This commit was originally because it was suspected to cause a crash,
but a reproducer did not surface.
A crash that was exposed by this change was fixed in 1d8f2e5292.
This reverts the revert commit 0581c0b0ee.
This patch adds isGuaranteedNotToBePoison and programUndefinedIfUndefOrPoison.
isGuaranteedNotToBePoison will be used at D75808. The latter function is used at isGuaranteedNotToBePoison.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D84242
Recognize umin/umax/smin/smax intrinsics and convert them to the
already existing SCEV nodes of the same name.
In the future we'll want SCEVExpander to also produce the intrinsics,
but we're not ready for that yet.
Differential Revision: https://reviews.llvm.org/D87160
This reverts commit e441b7a7a0.
This patch causes a compile error in tensorflow opensource project. The stack trace looks like:
Point of crash:
llvm/include/llvm/Analysis/LoopInfoImpl.h : line 35
(gdb) ptype *this
type = const class llvm::LoopBase<llvm::BasicBlock, llvm::Loop> [with BlockT = llvm::BasicBlock, LoopT = llvm::Loop]
(gdb) p *this
$1 = {ParentLoop = 0x0, SubLoops = std::vector of length 0, capacity 0, Blocks = std::vector of length 0, capacity 1,
DenseBlockSet = {<llvm::SmallPtrSetImpl<llvm::BasicBlock const*>> = {<llvm::SmallPtrSetImplBase> = {<llvm::DebugEpochBase> = {Epoch = 3}, SmallArray = 0x1b2bf6c8, CurArray = 0x1b2bf6c8,
CurArraySize = 8, NumNonEmpty = 0, NumTombstones = 0}, <No data fields>}, SmallStorage = {0xfffffffffffffffe, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}}, IsInvalid = true}
(gdb) p *this->DenseBlockSet->CurArray
$2 = (const void *) 0xfffffffffffffffe
I will try to get a case from tensorflow or use creduce to get a small case.
Now that SCEVExpander can preserve LCSSA form,
we do not have to worry about LCSSA form when
trying to look through PHIs. SCEVExpander will take
care of inserting LCSSA PHI nodes as required.
This increases precision of the analysis in some cases.
Reviewed By: mkazantsev, bmahjour
Differential Revision: https://reviews.llvm.org/D71539
This is the max version of D85046.
This change causes binary changes in 44 out of 237 benchmarks (out of
MultiSource/SPEC2000/SPEC2006)
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D85189
In some cases, it seems like we can get rid of unnecessary s/umins by
using information from the loop guards (unless I am missing something).
One place where this seems to be helpful in practice is when computing
loop trip counts. This patch just changes howManyGreaterThans for now.
Note that this requires a loop for which we can check 'is guarded'.
On SPEC2000/SPEC2006/MultiSource, there are some notable changes for
some programs in the number of loops unrolled and trip counts computed.
```
Same hash: 179 (filtered out)
Remaining: 58
Metric: scalar-evolution.NumTripCountsComputed
Program base patch diff
test-suite...langs-C/compiler/compiler.test 25.00 31.00 24.0%
test-suite.../Applications/SPASS/SPASS.test 2020.00 2323.00 15.0%
test-suite...langs-C/allroots/allroots.test 29.00 32.00 10.3%
test-suite.../Prolangs-C/loader/loader.test 17.00 18.00 5.9%
test-suite...fice-ispell/office-ispell.test 253.00 265.00 4.7%
test-suite...006/450.soplex/450.soplex.test 3552.00 3692.00 3.9%
test-suite...chmarks/MallocBench/gs/gs.test 453.00 470.00 3.8%
test-suite...ngs-C/assembler/assembler.test 29.00 30.00 3.4%
test-suite.../Benchmarks/Ptrdist/bc/bc.test 263.00 270.00 2.7%
test-suite...rks/FreeBench/pifft/pifft.test 722.00 741.00 2.6%
test-suite...count/automotive-bitcount.test 41.00 42.00 2.4%
test-suite...0/253.perlbmk/253.perlbmk.test 1417.00 1451.00 2.4%
test-suite...000/197.parser/197.parser.test 387.00 396.00 2.3%
test-suite...lications/sqlite3/sqlite3.test 1168.00 1189.00 1.8%
test-suite...000/255.vortex/255.vortex.test 173.00 176.00 1.7%
Metric: loop-unroll.NumUnrolled
Program base patch diff
test-suite...langs-C/compiler/compiler.test 1.00 3.00 200.0%
test-suite.../Applications/SPASS/SPASS.test 134.00 234.00 74.6%
test-suite...count/automotive-bitcount.test 3.00 4.00 33.3%
test-suite.../Prolangs-C/loader/loader.test 3.00 4.00 33.3%
test-suite...langs-C/allroots/allroots.test 3.00 4.00 33.3%
test-suite...Source/Benchmarks/sim/sim.test 10.00 12.00 20.0%
test-suite...fice-ispell/office-ispell.test 21.00 25.00 19.0%
test-suite.../Benchmarks/Ptrdist/bc/bc.test 32.00 38.00 18.8%
test-suite...006/450.soplex/450.soplex.test 300.00 352.00 17.3%
test-suite...rks/FreeBench/pifft/pifft.test 60.00 69.00 15.0%
test-suite...chmarks/MallocBench/gs/gs.test 57.00 63.00 10.5%
test-suite...ngs-C/assembler/assembler.test 10.00 11.00 10.0%
test-suite...0/253.perlbmk/253.perlbmk.test 145.00 157.00 8.3%
test-suite...000/197.parser/197.parser.test 43.00 46.00 7.0%
test-suite...TimberWolfMC/timberwolfmc.test 205.00 214.00 4.4%
Geomean difference 7.6%
```
Fixes https://bugs.llvm.org/show_bug.cgi?id=46939
Fixes https://bugs.llvm.org/show_bug.cgi?id=46924 on X86.
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D85046
This assert was added to verify assumption that GEP's SCEV will be of pointer type,
basing on fact that it should be a SCEVAddExpr with (at least) last operand being
pointer. Two notes:
- GEP's SCEV does not have to be a SCEVAddExpr after all simplifications;
- In current state, GEP's SCEV does not have to have at least one pointer operands
(all of them can become int during the transforms).
However, we might want to be at a point where it is true. We are currently removing
this assert and will try to enumerate the cases where "is pointer" notion might be
lost during the transforms. When all of them are fixed, we can return it.
Differential Revision: https://reviews.llvm.org/D84294
Reviewed By: lebedev.ri
Many tests use opt's -analyze feature, which does not translate well to
NPM and has better alternatives. The alternative here is to explicitly
add a pass that calls ScalarEvolution::print().
The legacy pass manager RUNs aren't changing, but they are now pinned to
the legacy pass manager. For each legacy pass manager RUN, I added a
corresponding NPM RUN using the 'print<scalar-evolution>' pass. For
compatibility with update_analyze_test_checks.py and existing test
CHECKs, 'print<scalar-evolution>' now prints what -analyze prints per
function.
This was generated by the following Python script and failures were
manually fixed up:
import sys
for i in sys.argv:
with open(i, 'r') as f:
s = f.read()
with open(i, 'w') as f:
for l in s.splitlines():
if "RUN:" in l and ' -analyze ' in l and '\\' not in l:
f.write(l.replace(' -analyze ', ' -analyze -enable-new-pm=0 '))
f.write('\n')
f.write(l.replace(' -analyze ', ' -disable-output ').replace(' -scalar-evolution ', ' "-passes=print<scalar-evolution>" ').replace(" | ", " 2>&1 | "))
f.write('\n')
else:
f.write(l)
There are a couple failures still in ScalarEvolution under NPM, but
those are due to other unrelated naming conflicts.
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D83798
Summary:
While InstCombine trivially converts that `srem` into a `urem`,
it might happen later than wanted, in particular i'd like
for that to happen on https://godbolt.org/z/bwuEmJ test case
early in pipeline, before first instcombine run, just before `-mem2reg`.
SCEV should recognize this case natively.
Reviewers: mkazantsev, efriedma, nikic, reames
Reviewed By: efriedma
Subscribers: clementval, hiraditya, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D82721
Summary:
The added assertion fails on the added test without the fix.
Reduced from test-suite/MultiSource/Benchmarks/MiBench/office-ispell/correct.c
In IR, getelementptr, obviously, takes pointer as it's base,
and returns a pointer.
When creating an SCEV expression, SCEV operands are sorted in hope
that it increases folding potential, and at the same time SCEVAddExpr's
type is the type of the last(!) operand.
Which means, in some exceedingly rare cases, pointer operand may happen to
end up not being the last operand, and as a result SCEV for GEP
will suddenly have a non-pointer return type.
We should ensure that does not happen.
In the end, actually storing the `Type *`, at the cost of increasing
memory footprint of `SCEVAddExpr`, appears to be the solution.
We can't just store a 'is a pointer' bit and create pointer type
on the fly since we don't have data layout in getType().
Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=46457 | PR46457 ]]
Reviewers: efriedma, mkazantsev, reames, nikic
Reviewed By: efriedma
Subscribers: hiraditya, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D82633
Summary:
This is boringly straight-forward, each iteration we see if
V is some expression that we can look into, and if it has
a single pointer operand, then set V to that operand
and repeat.
Reviewers: efriedma, mkazantsev, reames, nikic
Reviewed By: nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D82632
This makes it usable from outside of SCEV,
while previously it was internal to the ScalarEvolution.cpp
In particular, i want to use it in an WIP alloca promotion helper pass,
to analyze if some SCEV is a multiple of some other SCEV.
Move ScalarEvolution::forgetLoopDispositions implementation to ScalarEvolution.cpp to remove the dependency.
Add implicit header dependency to source files where necessary.
Change isa<> to a variadic function template, so that it can be used to test against one of multiple types as follows:
isa<Type0, Type1, Type2>(Val)
Differential Revision: https://reviews.llvm.org/D81045
Summary:
That's just really wrong. While sure, if LHS is AddRec, and we could
propagate it's no-wrap flags, that doesn't make, because as long as
the operands of `or` had no common bits set, then the `add`
of these operands will never overflow: http://volta.cs.utah.edu:8080/z/gmt7Sy
IOW we need no propagation/detection, we are free to just set NUW+NSW.
But as rG39e3683534c83573da5c8b70c8adfb43948f601f shows,
even when the old code failed to "deduce" flags,
we'd eventually re-deduce them somewhere, later.
So let's just set them.
Reviewers: mkazantsev, reames, sanjoy, efriedma
Reviewed By: efriedma
Subscribers: efriedma, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D81246
Summary:
There was this comment here previously:
```
- // It is currently not resolved how to interpret NSW for left
- // shift by BitWidth - 1, so we avoid applying flags in that
- // case. Remove this check (or this comment) once the situation
- // is resolved. See
- // http://lists.llvm.org/pipermail/llvm-dev/2015-April/084195.html
- // and http://reviews.llvm.org/D8890 .
```
But langref was fixed in rL286785, and the behavior is pretty obvious:
http://volta.cs.utah.edu:8080/z/MM4WZP
^ nuw can always be propagated. nsw can be propagated if
either nuw is specified, or the shift is by *less* than bitwidth-1.
This mimics similar D81189 Reassociate change, alive2 is happy about that one.
I'm not sure `NUW` isn't being printed, but that seems unrelated.
Reviewers: mkazantsev, reames, sanjoy, nlopes, craig.topper, efriedma
Reviewed By: efriedma
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D81243
Summary:
Users of SCEV reasonably assume that multiplication of two constant
SCEVs will in turn be constant.
However, that is not always the case:
First, we can get here with reached depth limit, and will create
MultExpr SCEV `C1 * C2` and cache it.
Then, we can get here with the same operands, but with small depth
level. But this time we will find existing MultExpr SCEV and return
it, instead of expected constant SCEV.
This patch changes getMultExpr to not apply depth limit to all constant
operands expression, allowing them to be folded.
Reviewers: reames, mkazantsev
Subscribers: hiraditya, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D79893
Summary:
This is RFC for fixes in poison-related functions of ValueTracking.
These functions assume that a value can be poison bitwisely, but the semantics
of bitwise poison is not clear at the moment.
Allowing a value to have bitwise poison adds complexity to reasoning about
correctness of optimizations.
This patch makes the analysis functions simply assume that a value is
either fully poison or not, which has been used to understand the correctness
of a few previous optimizations.
The bitwise poison semantics seems to be only used by these functions as well.
In terms of implementation, using value-wise poison concept makes existing
functions do more precise analysis, which is what this patch contains.
Reviewers: spatel, lebedev.ri, jdoerfert, reames, nikic, nlopes, regehr
Reviewed By: nikic
Subscribers: fhahn, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78503
Summary:
This is RFC for fixes in poison-related functions of ValueTracking.
These functions assume that a value can be poison bitwisely, but the semantics
of bitwise poison is not clear at the moment.
Allowing a value to have bitwise poison adds complexity to reasoning about
correctness of optimizations.
This patch makes the analysis functions simply assume that a value is
either fully poison or not, which has been used to understand the correctness
of a few previous optimizations.
The bitwise poison semantics seems to be only used by these functions as well.
In terms of implementation, using value-wise poison concept makes existing
functions do more precise analysis, which is what this patch contains.
Reviewers: spatel, lebedev.ri, jdoerfert, reames, nikic, nlopes, regehr
Reviewed By: nikic
Subscribers: fhahn, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78503
Now that we have scalable vectors, there's a distinction that isn't
getting captured in the original SequentialType: some vectors don't have
a known element count, so counting the number of elements doesn't make
sense.
In some cases, there's a better way to express the commonality using
other methods. If we're dealing with GEPs, there's GEP methods; if we're
dealing with a ConstantDataSequential, we can query its element type
directly.
In the relatively few remaining cases, I just decided to write out
the type checks. We're talking about relatively few places, and I think
the abstraction doesn't really carry its weight. (See thread "[RFC]
Refactor class hierarchy of VectorType in the IR" on llvmdev.)
Differential Revision: https://reviews.llvm.org/D75661
For the PHI node
%1 = phi [%A, %entry], [%X, %latch]
it is incorrect to use SCEV of backedge val %X as an exit value
of PHI unless %X is loop invariant.
This is because exit value of %1 is value of %X at one-before-last
iteration of the loop.
Reviewed By: Meinersbur
Differential Revision: https://reviews.llvm.org/D73181
Because we have to use a ConstantExpr at some point, the canonical form
isn't set in stone, but this seems reasonable.
The pretty sizeof(<vscale x 4 x i32>) dumping is a relic of ancient
LLVM; I didn't have to touch that code. :)
Differential Revision: https://reviews.llvm.org/D75887
Calculating SCEVs can be cumbersome, and may take very long time (even
hours, for very long expressions). To prevent recalculating expressions
over and over again, we cache them.
This change add cache queries to key positions, to prevent recalculation
of the expressions.
Fix PR43571.
Differential Revision: https://reviews.llvm.org/D70097
Summary:
This patch moves the getIndexExpressionsFromGEP function from polly
into ScalarEvolution so that both polly and DependenceAnalysis can
use it for the purpose of subscript delinearization when the array
sizes are not parametric.
Authored By: bmahjour
Reviewer: Meinersbur, sebpop, fhahn, dmgreen, grosser, etiotto, bollu
Reviewed By: Meinersbur
Subscribers: hiraditya, arphaman, Whitney, ppc-slack, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D73995
Summary:
This was a very odd API, where you had to pass a flag into a zext
function to say whether the extended bits really were zero or not. All
callers passed in a literal true or false.
I think it's much clearer to make the function name reflect the
operation being performed on the value we're tracking (rather than on
the KnownBits Zero and One fields), so zext means the value is being
zero extended and new function anyext means the value is being extended
with unknown bits.
NFC.
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D74482
Summary:
Loop unroll spends a lot of time in SCEVs processing in case when a function
contains hundreds of simple 'for' loops with a quite complex arrays indexes like
for (int i = 0; i < 8; ++i) {
for (int j = 0; j < 32; ++j) {
C[j*8+i] = B[j*32+i+128] + A[i*64+128];
}
}
for (int i = 0; i < 8; ++i) {
for (int j = 0; j < 8; ++j) {
for (int k = 0; k < 32; ++k) {
D[k*64+i*8+j] = D[k*64+i*8+j] + E[i+16] * C[k*8+j+256];
}
}
}
The patch improves loop unroll speed since isLoopBackedgeGuardedByCond takes
much less time than isLoopEntryGuardedByCond in the edge case.
Reviewers: skatkov, sanjoy, mkazantsev
Reviewed By: sanjoy
Subscribers: fhahn, hiraditya, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D72929
If addrecexpr has nuw flag, the value should never be less than its
start value and start value does not required to be SCEVConstant.
Reviewed By: nikic, sanjoy
Differential Revision: https://reviews.llvm.org/D71690
Teach SCEV about the @loop.decrement.reg intrinsic, which has exactly the same
semantics as a sub expression. This allows us to query hardware-loops, which
contain this @loop.decrement.reg intrinsic, so that we can calculate iteration
counts, exit values, etc. of hardwareloops.
This "int_loop_decrement_reg" intrinsic is defined as "IntrNoDuplicate". Thus,
while hardware-loops and tripcounts now become analysable by SCEV, this
prevents the usual loop transformations from applying transformations on
hardware-loops, which is what we want at this point, for which I have added
test cases for loopunrolling and IndVarSimplify and LFTR.
Differential Revision: https://reviews.llvm.org/D71563
GEP index size can be specified in the DataLayout, introduced in D42123. However, there were still places
in which getIndexSizeInBits was used interchangeably with getPointerSizeInBits. This notably caused issues
with Instcombine's visitPtrToInt; but the unit tests was incorrect, so this remained undiscovered.
This fixes the buildbot failures.
Differential Revision: https://reviews.llvm.org/D68328
Patch by Joseph Faulls!
GEP index size can be specified in the DataLayout, introduced in D42123. However, there were still places
in which getIndexSizeInBits was used interchangeably with getPointerSizeInBits. This notably caused issues
with Instcombine's visitPtrToInt; but the unit tests was incorrect, so this remained undiscovered.
Differential Revision: https://reviews.llvm.org/D68328
Patch by Joseph Faulls!
As it can be seen from accompanying cleanup, it is not unheard of
to write `~Known.Zero` meaning "what maximal value can this KnownBits
produce". But i think `~Known.Zero` isn't *that* self-explanatory,
as compared to a method with a name.
Note that not all `~Known.Zero` places were cleaned up,
only those where this arguably improves things.
New pass manager doesn't use verifyAnalysis, so currently there is no
way to call SCEV verification from command line when new PM is used.
This patch adds a pass that allows you to do that.
Reviewers: reames, fhahn, sanjoy.google, nikic
Reviewed By: fhahn
Subscribers: hiraditya, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70423
For the various trip-count tests, the classification isn't useful and makes the auto-generated tests super verbose. By skipping it, we make the auto-gen tests closer to the manually written ones. Up next: auto-genning a bunch of the existings tests.
Simple loop unswitch likes to leave around unsimplified and/or/xors. SCEV today bails out on these idioms which is unfortunate in general, and specifically for the unswitch interaction.
Differential Revision: https://reviews.llvm.org/D70459
This file lists every pass in LLVM, and is included by Pass.h, which is
very popular. Every time we add, remove, or rename a pass in LLVM, it
caused lots of recompilation.
I found this fact by looking at this table, which is sorted by the
number of times a file was changed over the last 100,000 git commits
multiplied by the number of object files that depend on it in the
current checkout:
recompiles touches affected_files header
342380 95 3604 llvm/include/llvm/ADT/STLExtras.h
314730 234 1345 llvm/include/llvm/InitializePasses.h
307036 118 2602 llvm/include/llvm/ADT/APInt.h
213049 59 3611 llvm/include/llvm/Support/MathExtras.h
170422 47 3626 llvm/include/llvm/Support/Compiler.h
162225 45 3605 llvm/include/llvm/ADT/Optional.h
158319 63 2513 llvm/include/llvm/ADT/Triple.h
140322 39 3598 llvm/include/llvm/ADT/StringRef.h
137647 59 2333 llvm/include/llvm/Support/Error.h
131619 73 1803 llvm/include/llvm/Support/FileSystem.h
Before this change, touching InitializePasses.h would cause 1345 files
to recompile. After this change, touching it only causes 550 compiles in
an incremental rebuild.
Reviewers: bkramer, asbirlea, bollu, jdoerfert
Differential Revision: https://reviews.llvm.org/D70211
This patch fixes two issues noticed by inspection when going to enable the loop predication code in IndVarSimplify.
Issue 1 - Both the LoopPredication transform, and the already on by default optimizeLoopExits transform, modify the exit count of the exits they modify. (either to 0 or Infinity) Looking at the code more closely, this was not reflected into SCEV and we were instead running later transforms with incorrect SCEVs. Fixing this requires forgetting the loop, weakening a too strong assert, and updating SCEV to not pessimize results when a loop is provable untaken. I haven't been able to find a test case to demonstrate the miscompile.
Issue 2 - For modules without a data layout, we can end up with unsized pointer typed exit counts. Just bail out of this case.
I think these are the last two issues which need addressed before we enable this by default. The code has already survived a decent amount of fuzzing without revealing either of the above.
Differential Revision: https://reviews.llvm.org/D69695
We were already going to all of the trouble of computing maximum constant exit counts for each loop exit, we might as well expose them through the API. The change in IndVars is mostly to demonstrate that the wired up code works, but it als very slightly strengthens the transform. The strengthened case is rather narrow though: it requires one exactly analyzeable exit, one imprecisely analyzeable exit (with the upper bound less than the precise one), and one unanalyzeable exit. I coudn't construct a reasonably stable test case.
This does increase the memory usage of the BackedgeTakenCount by a factor of 2 in the worst case.
I also noticed the loop in IndVars is O(#Exits ^ 2). This doesn't change with this patch. A future patch will cache this result inside of SCEV to avoid requering.
This is a first step in figuring out a proper API for maximum (non constant) exit counts. This may evolve a bit as we get experience with the API needs; suggestions very welcome. This patch just tried to provide a framework that we can later add maximum too in a clean and obvious way.
Summary:
This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790
Reviewers: courbet
Subscribers: arsenm, dschuff, jyknight, sdardis, jvesely, nhaehnle, sbc100, jgravelle-google, hiraditya, aheejin, fedor.sergeev, jrtc27, atanasyan, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69216
llvm-svn: 375398
This is a common idiom which arises after induction variables are widened, and we have two or more exit conditions. Interestingly, we don't have instcombine or instsimplify support for this either.
Differential Revision: https://reviews.llvm.org/D69006
llvm-svn: 375349
Currently -verify-scev only fails if there is a constant difference
between two BE counts. This misses a lot of cases.
This patch adds a -verify-scev-strict options, which fails for any
non-zero differences, if used together with -verify-scev.
With the stricter checking, some unit tests fail because
of mis-matches, especially around IndVarSimplify.
If there is no reason I am missing for just checking constant deltas, I
am planning on looking into the various failures.
Reviewers: efriedma, sanjoy.google, reames, atrick
Reviewed By: sanjoy.google
Differential Revision: https://reviews.llvm.org/D68592
llvm-svn: 374535
This reverts r366419 because the analysis performed is within the context of
the loop and it's only valid to add wrapping flags to "global" expressions if
they're always correct.
llvm-svn: 373184
At present, `-scalar-evolution-max-iterations` is a `cl::Optional`
option, which means it demands to be passed exactly zero or one times.
Our build system makes it pretty tricky to guarantee this. We often
accidentally pass the flag more than once (but always with the same
value) which results in an error, after which compilation fails:
```
clang (LLVM option parsing): for the -scalar-evolution-max-iterations option: may only occur zero or one times!
```
It seems reasonable to allow -scalar-evolution-max-iterations to be
passed more than once. Quoting the [[ http://llvm.org/docs/CommandLine.html#controlling-the-number-of-occurrences-required-and-allowed | documentation ]]:
> The cl::ZeroOrMore modifier ... indicates that your program will allow the option to be specified zero or more times.
> ...
> If an option is specified multiple times for an option of the cl::opt class, only the last value will be retained.
Original patch by: Enrico Bern Hardy Tanuwidjaja <etanuwid@fb.com>
Differential Revision: https://reviews.llvm.org/D67512
llvm-svn: 372346
We were failing to compute trip counts (both exact and maximum) for any loop which involved a comparison against either an umin or smin. It looks like this simply got missed when we added smin/umin to SCEV. (Note: umin was submitted separately earlier today. Turned out two folks hit this at the same time.)
Differential Revision: https://reviews.llvm.org/D67514
llvm-svn: 371776
This patch adds support for SCEVUMinExpr to getRangeRef,
similar to the support for SCEVUMaxExpr.
Reviewers: sanjoy.google, efriedma, reames, nikic
Reviewed By: sanjoy.google
Differential Revision: https://reviews.llvm.org/D67177
llvm-svn: 371768
Summary:
This is the first change to enable the TLI to be built per-function so
that -fno-builtin* handling can be migrated to use function attributes.
See discussion on D61634 for background. This is an enabler for fixing
handling of these options for LTO, for example.
This change should not affect behavior, as the provided function is not
yet used to build a specifically per-function TLI, but rather enables
that migration.
Most of the changes were very mechanical, e.g. passing a Function to the
legacy analysis pass's getTLI interface, or in Module level cases,
adding a callback. This is similar to the way the per-function TTI
analysis works.
There was one place where we were looking for builtins but not in the
context of a specific function. See FindCXAAtExit in
lib/Transforms/IPO/GlobalOpt.cpp. I'm somewhat concerned my workaround
could provide the wrong behavior in some corner cases. Suggestions
welcome.
Reviewers: chandlerc, hfinkel
Subscribers: arsenm, dschuff, jvesely, nhaehnle, mehdi_amini, javed.absar, sbc100, jgravelle-google, eraman, aheejin, steven_wu, george.burgess.iv, dexonsmith, jfb, asbirlea, gchatelet, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D66428
llvm-svn: 371284
Without this patch computeConstantDifference returns None for cases like
these:
computeConstantDifference(%x, %x)
computeConstantDifference({%x,+,16}, {%x,+,16})
Differential Revision: https://reviews.llvm.org/D65474
llvm-svn: 368193
We haven't changed the set of users, just specialized an operand for those users. Given that, the previous wrap flags must still be correct.
Sorry for the lack of test case. Noticed this while working on something else, and haven't figured out to exercise this standalone.
llvm-svn: 365053
The previous output was next to useless if *any* exit was not computable. If we have more than one exit, show the exit count for each so that it's easier to see what's going from with SCEV analysis when debugging.
llvm-svn: 364579
This patch really contains two pieces:
Teach SCEV how to fold a phi in the header of a loop to the value on the backedge when a) the backedge is known to execute at least once, and b) the value is safe to use globally within the scope dominated by the original phi.
Teach IndVarSimplify's rewriteLoopExitValues to allow loop invariant expressions which already exist (and thus don't need new computation inserted) even in loops where we can't optimize away other uses.
Differential Revision: https://reviews.llvm.org/D63224
llvm-svn: 363619
Based on D59959, this switches SCEV to use unsigned/signed range
intersection based on the sign hint. This will prefer non-wrapping
ranges in the relevant domain. I've left the one intersection in
getRangeForAffineAR() to use the smallest intersection heuristic,
as there doesn't seem to be any obvious preference there.
Differential Revision: https://reviews.llvm.org/D60035
llvm-svn: 363490
SCEV does not propagate arguments through one-input Phis so as to make it easy for the SCEV expander (and related code) to preserve LCSSA. It's not entirely clear this restriction is neccessary, but for the moment it exists. For this reason, we don't analyze single-entry phi inputs. However it is possible that when an this input leaves the loop through LCSSA Phi, it is a provable constant. Missing that results in an order of optimization issue in loop exit value rewriting where we miss some oppurtunities based on order in which we visit sibling loops.
This patch teaches computeSCEVAtScope about this case. We can generalize it later, but so far we can only replace LCSSA Phis with their constant loop-exiting values. We should probably also add similiar logic directly in the SCEV construction path itself.
Patch by: mkazantsev (with revised commit message by me)
Differential Revision: https://reviews.llvm.org/D58113
llvm-svn: 363180
The issue is that if we have a loop with multiple predecessors outside the loop, the code was expecting to merge them and only return if equal, but instead returned the first one seen.
I have no idea if this actually tripped anywhere. I noticed it by accident when reading the code and have no idea how to go about constructing a test case.
llvm-svn: 363112
Summary:
Currently we express umin as `~umax(~x, ~y)`. However, this becomes
a problem for operands in non-integral pointer spaces, because `~x`
is not something we can compute for `x` non-integral. However, since
comparisons are generally still allowed, we are actually able to
express `umin(x, y)` directly as long as we don't try to express is
as a umax. Support this by adding an explicit umin/smin representation
to SCEV. We do this by factoring the existing getUMax/getSMax functions
into a new function that does all four. The previous two functions were
largely identical.
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D50167
llvm-svn: 360159
Summary:
Commit
rL331949: SCEV] Do not use induction in isKnownPredicate for simplification umax
changed the codepath for umax from isKnownPredicate to
isKnownViaNonRecursiveReasoning to avoid compile time blow up (and as
I found out also stack overflows). However, there is an exact copy of
the code for umax that was lacking this change. In D50167 I want to unify
these codepaths, but to avoid that being a behavior change for the smax
case, pull this independent bit out of it.
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D61166
llvm-svn: 359693
This reverts commit 7bf4d7c07f2fac862ef34c82ad0fef6513452445.
After thinking about this more, this isn't right, the range is not exact
in the same sense as makeExactICmpRegion(). This needs a separate
function.
llvm-svn: 358876
Following D60632 makeGuaranteedNoWrapRegion() always returns an
exact nowrap region. Rename the function accordingly. This is in
line with the naming of makeExactICmpRegion().
llvm-svn: 358875
ConstantRanges have an annoying special case: If upper and lower are
the same, it can be either an empty or a full set. When constructing
constant ranges nearly always a full set is intended, but this still
requires an explicit check in many places.
This revision adds a getNonEmpty() constructor that disambiguates this
case: If upper and lower are the same, a full set is created.
Differential Revision: https://reviews.llvm.org/D60947
llvm-svn: 358854
This adds a WithOverflowInst class with a few helper methods to get
the underlying binop, signedness and nowrap type and makes use of it
where sensible. There will be two more uses in D60650/D60656.
The refactorings are all NFC, though I left some TODOs where things
could be improved. In particular we have two places where add/sub are
handled but mul isn't.
Differential Revision: https://reviews.llvm.org/D60668
llvm-svn: 358512
Summary:
Create a method to forget everything in SCEV.
Add a cl::opt and PassManagerBuilder option to use this in LoopUnroll.
Motivation: Certain Halide applications spend a very long time compiling in forgetLoop, and prefer to forget everything and rebuild SCEV from scratch.
Sample difference in compile time reduction: 21.04 to 14.78 using current ToT release build.
Testcase showcasing this cannot be opensourced and is fairly large.
The option disabled by default, but it may be desirable to enable by
default. Evidence in favor (two difference runs on different days/ToT state):
File Before (s) After (s)
clang-9.bc 7267.91 6639.14
llvm-as.bc 194.12 194.12
llvm-dis.bc 62.50 62.50
opt.bc 1855.85 1857.53
File Before (s) After (s)
clang-9.bc 8588.70 7812.83
llvm-as.bc 196.20 194.78
llvm-dis.bc 61.55 61.97
opt.bc 1739.78 1886.26
Reviewers: sanjoy
Subscribers: mehdi_amini, jlebar, zzheng, javed.absar, dmgreen, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60144
llvm-svn: 358304
Summary:
This lets us avoid e.g. checking if A >=s B in getSMaxExpr(A, B) if we've
already established that (A smax B) is the best we can do.
Fixes PR41225.
Reviewers: asbirlea
Subscribers: mcrosier, jlebar, bixia, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60010
llvm-svn: 357320
This adds ConstantRange::getFull(BitWidth) and
ConstantRange::getEmpty(BitWidth) named constructors as more readable
alternatives to the current ConstantRange(BitWidth, /* full */ false)
and similar. Additionally private getFull() and getEmpty() member
functions are added which return a full/empty range with the same bit
width -- these are commonly needed inside ConstantRange.cpp.
The IsFullSet argument in the ConstantRange(BitWidth, IsFullSet)
constructor is now mandatory for the few usages that still make use of it.
Differential Revision: https://reviews.llvm.org/D59716
llvm-svn: 356852
Summary:
This fixes an extremely long compile time caused by recursive analysis
of truncs, which were not previously subject to any depth limits unlike
some of the other ops. I decided to use the same control used for
sext/zext, since the routines analyzing these are sometimes mutually
recursive with the trunc analysis.
Reviewers: mkazantsev, sanjoy
Subscribers: sanjoy, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58994
llvm-svn: 355949
In some cases, MaxBECount can be less precise than ExactBECount for AND
and OR (the AND case was PR26207). In the OR test case, both ExactBECounts are
undef, but MaxBECount are different, so we hit the assertion below. This
patch uses the same solution the AND case already uses.
Assertion failed:
((isa<SCEVCouldNotCompute>(ExactNotTaken) || !isa<SCEVCouldNotCompute>(MaxNotTaken))
&& "Exact is not allowed to be less precise than Max"), function ExitLimit
This patch also consolidates test cases for both AND and OR in a single
test case.
Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=13245
Reviewers: sanjoy, efriedma, mkazantsev
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D58853
llvm-svn: 355259
The value stored in SCEVConstant is of type ConstantInt*, which can
never be UndefValue. So we should never hit that code.
Reviewers: mkazantsev, sanjoy
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D58851
llvm-svn: 355257
Currently, SCEV creates SCEVUnknown for every node of unreachable code. If we
have a huge amounts of such code, we will be littering SE with these nodes. We could
just state that they all are undef and save some memory.
Differential Revision: https://reviews.llvm.org/D57567
Reviewed By: sanjoy
llvm-svn: 353017
Currently SCEV attempts to limit transformations so that they do not work with
big SCEVs (that may take almost infinite compile time). But for this, it uses heuristics
such as recursion depth and number of operands, which do not give us a guarantee
that we don't actually have big SCEVs. This situation is still possible, though it is not
likely to happen. However, the bug PR33494 showed a bunch of simple corner case
tests where we still produce huge SCEVs, even not reaching big recursion depth etc.
This patch introduces a concept of 'huge' SCEVs. A SCEV is huge if its expression
size (intoduced in D35989) exceeds some threshold value. We prohibit optimizing
transformations if any of SCEVs we are dealing with is huge. This gives us a reliable
check that we don't spend too much time working with them.
As the next step, we can possibly get rid of old limiting mechanisms, such as recursion
depth thresholds.
Differential Revision: https://reviews.llvm.org/D35990
Reviewed By: reames
llvm-svn: 352728
The code of AddRec simplification is using wrong loop when it creates a new
AddRecExpr. It should be using AddRecLoop which we have saved and against which
all gate checks are made, and not calling AddRec->getLoop() over and over
again because AddRec may change and become an AddRecurrency from outer loop
during the transform iterations.
Considering this change trivial, commiting for postcommit review.
llvm-svn: 352451
This patch introduces the field `ExpressionSize` in SCEV. This field is
calculated only once on SCEV creation, and it represents the complexity of
this SCEV from arithmetical point of view (not from the point of the number
of actual different SCEV nodes that are used in the expression). Roughly
saying, it is the number of operands and operations symbols when we print this
SCEV.
A formal definition is following: if SCEV `X` has operands
`Op1`, `Op2`, ..., `OpN`,
then
Size(X) = 1 + Size(Op1) + Size(Op2) + ... + Size(OpN).
Size of SCEVConstant and SCEVUnknown is one.
Expression size may be used as a universal way to limit SCEV transformations
for huge SCEVs. Currently, we have a bunch of options that represents various
limits (such as recursion depth limit) that may not make any sense from the
point of view of a LLVM users who is not familiar with SCEV internals, and all
these different options pursue one goal. A more general rule that may
potentially allow us to get rid of this redundancy in options is "do not make
transformations with SCEVs of huge size". It can apply to all SCEV traversals
and transformations that may need to visit a SCEV node more than once, hence
they are prone to combinatorial explosions.
This patch only introduces SCEV sizes calculation as NFC, its utilization will
be introduced in follow-up patches.
Differential Revision: https://reviews.llvm.org/D35989
Reviewed By: reames
llvm-svn: 351725
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
We have a lot of various bugs that are caused by misuse of SCEV (in particular in LV),
all of them can simply be described as "we ask SCEV to prove some fact on invalid IR".
Some of examples of those are PR36311, PR37221, PR39160.
The problem is that these failues manifest differently (what we saw was failure of various
asserts across SCEV, but there can also be miscompiles). This patch adds an assert into two
SCEV methods that strongly rely on correctness of the IR and are involved in known failues.
This will at least allow us to have a clear indication of what was wrong in this case.
This patch also fixes a unit test with incorrect IR that fails this verification.
Differential Revision: https://reviews.llvm.org/D52930
Reviewed By: fhahn
llvm-svn: 346389
When we calculate a product of 2 AddRecs, we end up making quite massive
computations to deduce the operands of resulting AddRec. This process can
be optimized by computing all args of intermediate sum and then calling
`getAddExpr` once rather than calling `getAddExpr` with intermediate
result every time a new argument is computed.
Differential Revision: https://reviews.llvm.org/D53189
Reviewed By: rtereshin
llvm-svn: 345813
SCEV's transform that turns `{A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>` into
a single AddRec of size `2n+1` with complex combinatorial coefficients can easily
trigger exponential growth of the SCEV (in case if nothing gets folded and simplified).
We tried to restrain this transform using the option `scalar-evolution-max-add-rec-size`,
but its default value seems to be insufficiently small: the test attached to this patch
with default value of this option `16` has a SCEV of >3M symbols (when printed out).
This patch reduces the simplification limit. It is not a cure to combinatorial
explosions, but at least it reduces this corner case to something more or less
reasonable.
Differential Revision: https://reviews.llvm.org/D53282
Reviewed By: sanjoy
llvm-svn: 344584
by `getTerminator()` calls instead be declared as `Instruction`.
This is the biggest remaining chunk of the usage of `getTerminator()`
that insists on the narrow type and so is an easy batch of updates.
Several files saw more extensive updates where this would cascade to
requiring API updates within the file to use `Instruction` instead of
`TerminatorInst`. All of these were trivial in nature (pervasively using
`Instruction` instead just worked).
llvm-svn: 344502
This reverts r319889.
Unfortunately, wrapping flags are not a part of SCEV's identity (they
do not participate in computing a hash value or in equality
comparisons) and in fact they could be assigned after the fact w/o
rebuilding a SCEV.
Grep for const_cast's to see quite a few of examples, apparently all
for AddRec's at the moment.
So, if 2 expressions get built in 2 slightly different ways: one with
flags set in the beginning, the other with the flags attached later
on, we may end up with 2 expressions which are exactly the same but
have their operands swapped in one of the commutative N-ary
expressions, and at least one of them will have "sorted by complexity"
invariant broken.
2 identical SCEV's won't compare equal by pointer comparison as they
are supposed to.
A real-world reproducer is added as a regression test: the issue
described causes 2 identical SCEV expressions to have different order
of operands and therefore compare not equal, which in its turn
prevents LoadStoreVectorizer from vectorizing a pair of consecutive
loads.
On a larger example (the source of the test attached, which is a
bugpoint) I have seen even weirder behavior: adding a constant to an
existing SCEV changes the order of the existing terms, for instance,
getAddExpr(1, ((A * B) + (C * D))) returns (1 + (C * D) + (A * B)).
Differential Revision: https://reviews.llvm.org/D40645
llvm-svn: 340777
as well as sext(C + x + ...) -> (D + sext(C-D + x + ...))<nuw><nsw>
similar to the equivalent transformation for zext's
if the top level addition in (D + (C-D + x * n)) could be proven to
not wrap, where the choice of D also maximizes the number of trailing
zeroes of (C-D + x * n), ensuring homogeneous behaviour of the
transformation and better canonicalization of such AddRec's
(indeed, there are 2^(2w) different expressions in `B1 + ext(B2 + Y)` form for
the same Y, but only 2^(2w - k) different expressions in the resulting `B3 +
ext((B4 * 2^k) + Y)` form, where w is the bit width of the integral type)
This patch generalizes sext(C1 + C2*X) --> sext(C1) + sext(C2*X) and
sext{C1,+,C2} --> sext(C1) + sext{0,+,C2} transformations added in
r209568 relaxing the requirements the following way:
1. C2 doesn't have to be a power of 2, it's enough if it's divisible by 2
a sufficient number of times;
2. C1 doesn't have to be less than C2, instead of extracting the entire
C1 we can split it into 2 terms: (00...0XXX + YY...Y000), keep the
second one that may cause wrapping within the extension operator, and
move the first one that doesn't affect wrapping out of the extension
operator, enabling further simplifications;
3. C1 and C2 don't have to be positive, splitting C1 like shown above
produces a sum that is guaranteed to not wrap, signed or unsigned;
4. in AddExpr case there could be more than 2 terms, and in case of
AddExpr the 2nd and following terms and in case of AddRecExpr the
Step component don't have to be in the C2*X form or constant
(respectively), they just need to have enough trailing zeros,
which in turn could be guaranteed by means other than arithmetics,
e.g. by a pointer alignment;
5. the extension operator doesn't have to be a sext, the same
transformation works and profitable for zext's as well.
Apparently, optimizations like SLPVectorizer currently fail to
vectorize even rather trivial cases like the following:
double bar(double *a, unsigned n) {
double x = 0.0;
double y = 0.0;
for (unsigned i = 0; i < n; i += 2) {
x += a[i];
y += a[i + 1];
}
return x * y;
}
If compiled with `clang -std=c11 -Wpedantic -Wall -O3 main.c -S -o - -emit-llvm`
(!{!"clang version 7.0.0 (trunk 337339) (llvm/trunk 337344)"})
it produces scalar code with the loop not unrolled with the unsigned `n` and
`i` (like shown above), but vectorized and unrolled loop with signed `n` and
`i`. With the changes made in this commit the unsigned version will be
vectorized (though not unrolled for unclear reasons).
How it all works:
Let say we have an AddExpr that looks like (C + x + y + ...), where C
is a constant and x, y, ... are arbitrary SCEVs. Let's compute the
minimum number of trailing zeroes guaranteed of that sum w/o the
constant term: (x + y + ...). If, for example, those terms look like
follows:
i
XXXX...X000
YYYY...YY00
...
ZZZZ...0000
then the rightmost non-guaranteed-zero bit (a potential one at i-th
position above) can change the bits of the sum to the left (and at
i-th position itself), but it can not possibly change the bits to the
right. So we can compute the number of trailing zeroes by taking a
minimum between the numbers of trailing zeroes of the terms.
Now let's say that our original sum with the constant is effectively
just C + X, where X = x + y + .... Let's also say that we've got 2
guaranteed trailing zeros for X:
j
CCCC...CCCC
XXXX...XX00 // this is X = (x + y + ...)
Any bit of C to the left of j may in the end cause the C + X sum to
wrap, but the rightmost 2 bits of C (at positions j and j - 1) do not
affect wrapping in any way. If the upper bits cause a wrap, it will be
a wrap regardless of the values of the 2 least significant bits of C.
If the upper bits do not cause a wrap, it won't be a wrap regardless
of the values of the 2 bits on the right (again).
So let's split C to 2 constants like follows:
0000...00CC = D
CCCC...CC00 = (C - D)
and represent the whole sum as D + (C - D + X). The second term of
this new sum looks like this:
CCCC...CC00
XXXX...XX00
----------- // let's add them up
YYYY...YY00
The sum above (let's call it Y)) may or may not wrap, we don't know,
so we need to keep it under a sext/zext. Adding D to that sum though
will never wrap, signed or unsigned, if performed on the original bit
width or the extended one, because all that that final add does is
setting the 2 least significant bits of Y to the bits of D:
YYYY...YY00 = Y
0000...00CC = D
----------- <nuw><nsw>
YYYY...YYCC
Which means we can safely move that D out of the sext or zext and
claim that the top-level sum neither sign wraps nor unsigned wraps.
Let's run an example, let's say we're working in i8's and the original
expression (zext's or sext's operand) is 21 + 12x + 8y. So it goes
like this:
0001 0101 // 21
XXXX XX00 // 12x
YYYY Y000 // 8y
0001 0101 // 21
ZZZZ ZZ00 // 12x + 8y
0000 0001 // D
0001 0100 // 21 - D = 20
ZZZZ ZZ00 // 12x + 8y
0000 0001 // D
WWWW WW00 // 21 - D + 12x + 8y = 20 + 12x + 8y
therefore zext(21 + 12x + 8y) = (1 + zext(20 + 12x + 8y))<nuw><nsw>
This approach could be improved if we move away from using trailing
zeroes and use KnownBits instead. For instance, with KnownBits we could
have the following picture:
i
10 1110...0011 // this is C
XX X1XX...XX00 // this is X = (x + y + ...)
Notice that some of the bits of X are known ones, also notice that
known bits of X are interspersed with unknown bits and not grouped on
the rigth or left.
We can see at the position i that C(i) and X(i) are both known ones,
therefore the (i + 1)th carry bit is guaranteed to be 1 regardless of
the bits of C to the right of i. For instance, the C(i - 1) bit only
affects the bits of the sum at positions i - 1 and i, and does not
influence if the sum is going to wrap or not. Therefore we could split
the constant C the following way:
i
00 0010...0011 = D
10 1100...0000 = (C - D)
Let's compute the KnownBits of (C - D) + X:
XX1 1 = carry bit, blanks stand for known zeroes
10 1100...0000 = (C - D)
XX X1XX...XX00 = X
--- -----------
XX X0XX...XX00
Will this add wrap or not essentially depends on bits of X. Adding D
to this sum, however, is guaranteed to not to wrap:
0 X
00 0010...0011 = D
sX X0XX...XX00 = (C - D) + X
--- -----------
sX XXXX XX11
As could be seen above, adding D preserves the sign bit of (C - D) +
X, if any, and has a guaranteed 0 carry out, as expected.
The more bits of (C - D) we constrain, the better the transformations
introduced here canonicalize expressions as it leaves less freedom to
what values the constant part of ((C - D) + x + y + ...) can take.
Reviewed By: mzolotukhin, efriedma
Differential Revision: https://reviews.llvm.org/D48853
llvm-svn: 337943
if the top level addition in (D + (C-D + x + ...)) could be proven to
not wrap, where the choice of D also maximizes the number of trailing
zeroes of (C-D + x + ...), ensuring homogeneous behaviour of the
transformation and better canonicalization of such expressions.
This enables better canonicalization of expressions like
1 + zext(5 + 20 * %x + 24 * %y) and
zext(6 + 20 * %x + 24 * %y)
which get both transformed to
2 + zext(4 + 20 * %x + 24 * %y)
This pattern is common in address arithmetics and the transformation
makes it easier for passes like LoadStoreVectorizer to prove that 2 or
more memory accesses are consecutive and optimize (vectorize) them.
Reviewed By: mzolotukhin
Differential Revision: https://reviews.llvm.org/D48853
llvm-svn: 337859
SCEV tries to constant-fold arguments of trunc operands in SCEVAddExpr, and when it does
that, it passes wrong flags into the recursion. It is only valid to pass flags that are proved for
narrow type into a computation in wider type if we can prove that trunc instruction doesn't
actually change the value. If it did lose some meaningful bits, we may end up proving wrong
no-wrap flags for sum of arguments of trunc.
In the provided test we end up with `nuw` where it shouldn't be because of this bug.
The solution is to conservatively pass `SCEV::FlagAnyWrap` which is always a valid thing to do.
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D49471
llvm-svn: 337435
It's a bit neater to write T.isIntOrPtrTy() over `T.isIntegerTy() ||
T.isPointerTy()`.
I used Python's re.sub with this regex to update users:
r'([\w.\->()]+)isIntegerTy\(\)\s*\|\|\s*\1isPointerTy\(\)'
llvm-svn: 336462
Summary:
Comment on Transforms/LoopVersioning/incorrect-phi.ll: With the change
SCEV is able to prove that the loop doesn't wrap-self (due to zext i16
to i64), disabling the entire loop versioning pass. Removed the zext and
just use i64.
Reviewers: sanjoy
Subscribers: jlebar, hiraditya, javed.absar, bixia, llvm-commits
Differential Revision: https://reviews.llvm.org/D48409
llvm-svn: 336140
We can have AddRec with loops having many predecessors.
This changes an assert to an early return.
Differential Revision: https://reviews.llvm.org/D48766
llvm-svn: 335965
Summary:
This initiates a discussion on changing Polly accordingly while re-applying r335197 (D48338).
I have never worked on Polly. The proposed change to param_div_div_div_2.ll is not educated, but just patterns that match the output.
All LLVM files are already reviewed in D48338.
Reviewers: jdoerfert, bollu, efriedma
Subscribers: jlebar, sanjoy, hiraditya, llvm-commits, bixia
Differential Revision: https://reviews.llvm.org/D48453
llvm-svn: 335292
Summary:
Try to match udiv and urem patterns, and sink zext down to the leaves.
I'm not entirely sure why some unrelated tests change, but the added <nsw>s seem right.
Reviewers: sanjoy
Subscribers: jlebar, hiraditya, bixia, llvm-commits
Differential Revision: https://reviews.llvm.org/D48338
llvm-svn: 335197
This reverts r334428. It incorrectly marks some multiplications as nuw. Tim
Shen is working on a proper fix.
Original commit message:
[SCEV] Add nuw/nsw to mul ops in StrengthenNoWrapFlags where safe.
Summary:
Previously we would add them for adds, but not multiplies.
llvm-svn: 335016
Summary:
Sending for presubmit review out of an abundance of caution; it would be
bad to mess this up.
Reviewers: sanjoy
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D48238
llvm-svn: 334875
Summary:
Obviates the need for mask/clear/setFlags helpers.
There are some expressions here which can be simplified, but to keep
this easy to review, I have not simplified them in this patch.
No functional change.
Reviewers: sanjoy
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D48237
llvm-svn: 334874
Summary:
Specifically, we transform
zext(2^K * (trunc X to iN)) to iM ->
2^K * (zext(trunc X to i{N-K}) to iM)<nuw>
This is helpful because pulling the 2^K out of the zext allows further
optimizations.
Reviewers: sanjoy
Subscribers: hiraditya, llvm-commits, timshen
Differential Revision: https://reviews.llvm.org/D48158
llvm-svn: 334737
Summary:
Previously we would do this simplification only if it did not introduce
any new truncs (excepting new truncs which replace other cast ops).
This change weakens this condition: If the number of truncs stays the
same, but we're able to transform trunc(X + Y) to X + trunc(Y), that's
still simpler, and it may open up additional transformations.
While we're here, also clean up some duplicated code.
Reviewers: sanjoy
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D48160
llvm-svn: 334736
Summary:
Previously we would add them for adds, but not multiplies.
Reviewers: sanjoy
Subscribers: llvm-commits, hiraditya
Differential Revision: https://reviews.llvm.org/D48038
llvm-svn: 334428
An expression like
(zext i2 {(trunc i32 (1 + %B) to i2),+,1}<%while.body> to i32)
will become zero exactly when the nested value becomes zero in its type.
Strip injective operations from the input value in howFarToZero to make
the value simpler.
Differential Revision: https://reviews.llvm.org/D47951
llvm-svn: 334318
The DEBUG() macro is very generic so it might clash with other projects.
The renaming was done as follows:
- git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
- git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
- Manual change to APInt
- Manually chage DOCS as regex doesn't match it.
In the transition period the DEBUG() macro is still present and aliased
to the LLVM_DEBUG() one.
Differential Revision: https://reviews.llvm.org/D43624
llvm-svn: 332240
During simplification umax we trigger isKnownPredicate twice. As a first attempt it
tries the induction. To do that it tries to get post increment of SCEV.
Re-writing the SCEV may result in simplification of umax. If the SCEV contains a lot
of umax operations this recursion becomes very slow.
The added test demonstrates the slow behavior.
To resolve this we use only simple ways to check whether the predicate is known.
Reviewers: sanjoy, mkazantsev
Reviewed By: sanjoy
Subscribers: lebedev.ri, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D46046
llvm-svn: 331949
This patch was temporarily reverted because it has exposed bug 37229 on
PowerPC platform. The bug is unrelated to the patch and was just a general
bug in the optimization done for PowerPC platform only. The bug was fixed
by the patch rL331410.
This patch returns the disabled commit since the bug was fixed.
llvm-svn: 331427
See r331124 for how I made a list of files missing the include.
I then ran this Python script:
for f in open('filelist.txt'):
f = f.strip()
fl = open(f).readlines()
found = False
for i in xrange(len(fl)):
p = '#include "llvm/'
if not fl[i].startswith(p):
continue
if fl[i][len(p):] > 'Config':
fl.insert(i, '#include "llvm/Config/llvm-config.h"\n')
found = True
break
if not found:
print 'not found', f
else:
open(f, 'w').write(''.join(fl))
and then looked through everything with `svn diff | diffstat -l | xargs -n 1000 gvim -p`
and tried to fix include ordering and whatnot.
No intended behavior change.
llvm-svn: 331184
The invocation of getExact in ScalarEvolution::getBackedgeTakenInfo is used
only for getting statistic and for assert.
Even if statistics is disabled, the code related to it will be eliminated
the invocation to getExact itself will not be eliminated
because it may have side-effects like creation of new SCEVs.
So do invocation only when we collect statistics or executes asserts.
Reviewers: mkazantsev, sanjoy, javed.absar
Reviewed By: javed.absar
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D46178
llvm-svn: 331099
Add new umin creation method which accepts a list of operands.
SCEV does not represents umin which is required in getExact, so
it transforms umin to umax with not. As a result the transformation of
tree of max to max with several operands does not work.
We just use the new introduced method for creation umin from several operands.
Reviewers: sanjoy, mkazantsev
Reviewed By: sanjoy
Subscribers: javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D46047
llvm-svn: 331015
This reverts commit 023c8be90980e0180766196cba86f81608b35d38.
This patch triggers miscompile of zlib on PowerPC platform. Most likely it is
caused by some pre-backend PPC-specific pass, but we don't clearly know the
reason yet. So we temporally revert this patch with intention to return it
once the problem is resolved. See bug 37229 for details.
llvm-svn: 330893
In the function `simplifyOneLoop` we optimistically assume that changes in the
inner loop only affect this very loop and have no impact on its parents. In fact,
after rL329047 has been merged, we can now calculate exit counts for outer
loops which may depend on inner loops. Thus, we need to invalidate all parents
when we do something to a loop.
There is an evidence of incorrect behavior of `simplifyOneLoop`: when we insert
`SE->verify()` check in the end of this funciton, it fails on a bunch of existing
test, in particular:
LLVM :: Transforms/LoopUnroll/peel-loop-not-forced.ll
LLVM :: Transforms/LoopUnroll/peel-loop-pgo.ll
LLVM :: Transforms/LoopUnroll/peel-loop.ll
LLVM :: Transforms/LoopUnroll/peel-loop2.ll
Note that previously we have fixed issues of this variety, see rL328483.
This patch makes this function invalidate the outermost loop properly.
Differential Revision: https://reviews.llvm.org/D45937
Reviewed By: chandlerc
llvm-svn: 330576
This patch teaches SCEV how to prove implications for SCEVUnknown nodes that are Phis.
If we need to prove `Pred` for `LHS, RHS`, and `LHS` is a Phi with possible incoming values
`L1, L2, ..., LN`, then if we prove `Pred` for `(L1, RHS), (L2, RHS), ..., (LN, RHS)` then we can also
prove it for `(LHS, RHS)`. If both `LHS` and `RHS` are Phis from the same block, it is sufficient
to prove the predicate for values that come from the same predecessor block.
The typical case that it handles is that we sometimes need to prove that `Phi(Len, Len - 1) >= 0`
given that `Len > 0`. The new logic was added to `isImpliedViaOperations` and only uses it and
non-recursive reasoning to prove the facts we need, so it should not hurt compile time a lot.
Differential Revision: https://reviews.llvm.org/D44001
Reviewed By: anna
llvm-svn: 329150
The patch changes the usage of dominate to properlyDominate
to satisfy the condition !(a < a) while using std::max.
It is actually NFC due to set data structure is used to keep
the Loops and no two identical loops can be in collection.
So in reality there is no difference between usage of
dominate and properlyDominate in this particular case.
However it might be changed so it is better to fix it.
llvm-svn: 329051
Current implementation of `computeExitLimit` has a big piece of code
the only purpose of which is to prove that after the execution of this
block the latch will be executed. What it currently checks is actually a
subset of situations where the exiting block dominates latch.
This patch replaces all these checks for simple particular cases with
domination check over loop's latch which is the only necessary condition
of taking the exiting block into consideration. This change allows to
calculate exact loop taken count for simple loops like
for (int i = 0; i < 100; i++) {
if (cond) {...} else {...}
if (i > 50) break;
. . .
}
Differential Revision: https://reviews.llvm.org/D44677
Reviewed By: efriedma
llvm-svn: 329047
Summary:
r327219 added wrappers to std::sort which randomly shuffle the container before sorting.
This will help in uncovering non-determinism caused due to undefined sorting
order of objects having the same key.
To make use of that infrastructure we need to invoke llvm::sort instead of std::sort.
Note: This patch is one of a series of patches to replace *all* std::sort to llvm::sort.
Refer D44363 for a list of all the required patches.
Reviewers: sanjoy, dexonsmith, hfinkel, RKSimon
Reviewed By: dexonsmith
Subscribers: david2050, llvm-commits
Differential Revision: https://reviews.llvm.org/D44944
llvm-svn: 328925
Currently, `getExact` fails if it sees two exit counts in different blocks. There is
no solid reason to do so, given that we only calculate exact non-taken count
for exiting blocks that dominate latch. Using this fact, we can simply take min
out of all exits of all blocks to get the exact taken count.
This patch makes the calculation more optimistic with enforcing our assumption
with asserts. It allows us to calculate exact backedge taken count in trivial loops
like
for (int i = 0; i < 100; i++) {
if (i > 50) break;
. . .
}
Differential Revision: https://reviews.llvm.org/D44676
Reviewed By: fhahn
llvm-svn: 328611
This patch teaches `computeConstantDifference` handle calculation of constant
difference between `(X + C1)` and `(X + C2)` which is `(C2 - C1)`.
Differential Revision: https://reviews.llvm.org/D43759
Reviewed By: anna
llvm-svn: 328609
Summary:
Revert r325687 workaround for PR36032 since
a fix was committed in r326154.
Reviewers: sbaranga
Differential Revision: http://reviews.llvm.org/D44768
From: Evgeny Stupachenko <evstupac@gmail.com>
<evgeny.v.stupachenko@intel.com>
llvm-svn: 328257
This is re-land of https://reviews.llvm.org/rL327362 with a fix
and regression test.
The crash was due to it is possible that for found MDL loop,
LHS or RHS may contain an invariant unknown SCEV which
does not dominate the MDL. Please see regression
test for an example.
Reviewers: sanjoy, mkazantsev, reames
Reviewed By: mkazantsev
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D44553
llvm-svn: 327822
Methods `computeExitLimitFromCondCached` and `computeExitLimitFromCondImpl` take
true and false branches as parameters and only use them for asserts and for identifying
whether true/false branch belongs to the loop (which can be done once earlier). This fact
complicates generalization of exit limit computation logic on guards because the guards
don't have blocks to which they go in case of failure explicitly.
The motivation of this patch is that currently this part of SCEV knows nothing about guards
and only works with explicit branches. As result, it fails to prove that a loop
for (i = 0; i < 100; i++)
guard(i < 10);
exits after 10th iteration, while in the equivalent example
for (i = 0; i < 100; i++)
if (i >= 10) break;
SCEV easily proves this fact. We are going to change it in near future, and this is why
we need to make these methods operate on more abstract level.
This patch refactors this code to get rid of these parameters as meaningless and prepare
ground for teaching these methods to work with guards as well as they work with explicit
branching instructions.
Differential Revision: https://reviews.llvm.org/D44419
llvm-svn: 327615
isAvailableAtLoopEntry duplicates logic of `properlyDominates` after checking invariance.
This patch replaces this logic with invocation of this method which is more profitable
because it supports caching.
Differential Revision: https://reviews.llvm.org/D43997
llvm-svn: 327373
It is a revert of rL327362 which causes build bot failures with assert like
Assertion `isAvailableAtLoopEntry(RHS, L) && "RHS is not available at Loop Entry"' failed.
llvm-svn: 327363
IsKnownPredicate is updated to implement the following algorithm
proposed by @sanjoy and @mkazantsev :
isKnownPredicate(Pred, LHS, RHS) {
Collect set S all loops on which either LHS or RHS depend.
If S is non-empty
a. Let PD be the element of S which is dominated by all other elements of S
b. Let E(LHS) be value of LHS on entry of PD.
To get E(LHS), we should just take LHS and replace all AddRecs that
are attached to PD on with their entry values.
Define E(RHS) in the same way.
c. Let B(LHS) be value of L on backedge of PD.
To get B(LHS), we should just take LHS and replace all AddRecs that
are attached to PD on with their backedge values.
Define B(RHS) in the same way.
d. Note that E(LHS) and E(RHS) are automatically available on entry of PD,
so we can assert on that.
e. Return true if isLoopEntryGuardedByCond(Pred, E(LHS), E(RHS)) &&
isLoopBackedgeGuardedByCond(Pred, B(LHS), B(RHS))
Return true if Pred, L, R is known from ranges, splitting etc.
}
This is follow-up for https://reviews.llvm.org/D42417.
Reviewers: sanjoy, mkazantsev, reames
Reviewed By: sanjoy, mkazantsev
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D43507
llvm-svn: 327362
The range of SCEVUnknown Phi which merges values `X1, X2, ..., XN`
can be evaluated as `U(Range(X1), Range(X2), ..., Range(XN))`.
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D43810
llvm-svn: 326418
Set default value for IgnoreOtherLoops of SCEVInitRewriter::rewrite to true
to be consistent with SCEVPostIncRewriter which does not have this parameter
but behaves as it would be true.
This is follow up for rL326067.
llvm-svn: 326174
The patch introduces the new function in ScalarEvolution to get
all loops used in specified SCEV.
This is a preparation for re-writing isKnownPredicate utility as
described in https://reviews.llvm.org/D42417.
Reviewers: sanjoy, mkazantsev, reames
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D43504
llvm-svn: 326072
The patch introduces the SCEVPostIncRewriter rewriter which
is similar to SCEVInitRewriter but rewrites AddRec with post increment
value of this AddRec.
This is a preparation for re-writing isKnownPredicate utility as
described in https://reviews.llvm.org/D42417.
Reviewers: sanjoy, mkazantsev, reames
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D43499
llvm-svn: 326071
The patch introduces an additional parameter IgnoreOtherLoops to SCEVInitRewriter.
if it is equal to true then rewriter will not invalidate result in case
SCEV depends on other loops then specified during creation.
The patch does not change the default behavior.
This is a preparation for re-writing isKnownPredicate utility as
described in https://reviews.llvm.org/D42417.
Reviewers: sanjoy, mkazantsev, reames
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D43498
llvm-svn: 326067
SCEV has multiple occurences of code when we need to prove some predicate on
every iteration of a loop and do it with invocations of couple `isLoopEntryGuardedByCond`,
`isLoopBackedgeGuardedByCond`. This patch factors out these two calls into a separate
method. It is a preparation step to extend this logic: it is not the only way how we can prove
such conditions.
Differential Revision: https://reviews.llvm.org/D43373
llvm-svn: 325745
of turning SCEVUnknowns of PHIs into AddRecExprs.
This feature is now hidden behind the -scev-version-unknown flag.
Fixes PR36032 and PR35432.
llvm-svn: 325687
There is a more powerful but still simple function `isKnownViaSimpleReasoning ` that
does constant range check and few more additional checks. We use it some places (e.g.
when proving implications) and in some other places we only check constant ranges.
Currently, indvar simplifier fails to remove the check in following loop:
int inc = ...;
for (int i = inc, j = inc - 1; i < 200; ++i, ++j)
if (i > j) { ... }
This patch replaces all usages of `isKnownPredicateViaConstantRanges` with
`isKnownViaSimpleReasoning` to have smarter proofs. In particular, it fixes the
case above.
Reviewed-By: sanjoy
Differential Revision: https://reviews.llvm.org/D43175
llvm-svn: 325214
Making a width of GEP Index, which is used for address calculation, to be one of the pointer properties in the Data Layout.
p[address space]:size:memory_size:alignment:pref_alignment:index_size_in_bits.
The index size parameter is optional, if not specified, it is equal to the pointer size.
Till now, the InstCombiner normalized GEPs and extended the Index operand to the pointer width.
It works fine if you can convert pointer to integer for address calculation and all registered targets do this.
But some ISAs have very restricted instruction set for the pointer calculation. During discussions were desided to retrieve information for GEP index from the Data Layout.
http://lists.llvm.org/pipermail/llvm-dev/2018-January/120416.html
I added an interface to the Data Layout and I changed the InstCombiner and some other passes to take the Index width into account.
This change does not affect any in-tree target. I added tests to cover data layouts with explicitly specified index size.
Differential Revision: https://reviews.llvm.org/D42123
llvm-svn: 325102
The current implementation of `getPostIncExpr` invokes `getAddExpr` for two recurrencies
and expects that it always returns it a recurrency. But this is not guaranteed to happen if we
have reached max recursion depth or refused to make SCEV simplification for other reasons.
This patch changes its implementation so that now it always returns SCEVAddRec without
relying on `getAddExpr`.
Differential Revision: https://reviews.llvm.org/D42953
llvm-svn: 324866
The failures happened because of assert which was overconfident about
SCEV's proving capabilities and is generally not valid.
Differential Revision: https://reviews.llvm.org/D42835
llvm-svn: 324473
Sometimes `isLoopEntryGuardedByCond` cannot prove predicate `a > b` directly.
But it is a common situation when `a >= b` is known from ranges and `a != b` is
known from a dominating condition. Thia patch teaches SCEV to sum these facts
together and prove strict comparison via non-strict one.
Differential Revision: https://reviews.llvm.org/D42835
llvm-svn: 324453
ScalarEvolution::isKnownPredicate invokes isLoopEntryGuardedByCond without check
that SCEV is available at entry point of the loop. It is incorrect and fixed by patch.
To bugs additionally fixed:
assert is moved after the check whether loop is not a nullptr.
Usage of isLoopEntryGuardedByCond in ScalarEvolution::isImpliedCondOperandsViaNoOverflow
is guarded by isAvailableAtLoopEntry.
Reviewers: sanjoy, mkazantsev, anna, dorit, reames
Reviewed By: mkazantsev
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D42417
llvm-svn: 324204
ScalarEvolution::isKnownPredicate invokes isLoopEntryGuardedByCond without check
that SCEV is available at entry point of the loop. It is incorrect and fixed by patch.
Reviewers: sanjoy, mkazantsev, anna, dorit
Reviewed By: mkazantsev
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D42165
llvm-svn: 323077
SCEV tracks the correspondence of created SCEV to original instruction.
However during creation of SCEV it is possible that nuw/nsw/exact flags are
lost.
As a result during expansion of the SCEV the instruction with nuw/nsw/exact
will be used where it was expected and we produce poison incorreclty.
Reviewers: sanjoy, mkazantsev, sebpop, jbhateja
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D41578
llvm-svn: 322058
This is fix for the crash caused by ScalarEvolution::getTruncateExpr.
It expects that if it checked the condition that SCEV is not in UniqueSCEVs cache in
the beginning that it will not be there inside this method.
However during recursion and transformation/simplification for sub expression,
it is possible that these modifications will end up with the same SCEV as we started from.
So we must always check whether SCEV is in cache and do not insert item if it is already there.
Reviewers: sanjoy, mkazantsev, craig.topper
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D41380
llvm-svn: 321472
D30041 extended SCEVPredicateRewriter to improve handling of Phi nodes whose
update chain involves casts; PSCEV can now build an AddRecurrence for some
forms of such phi nodes, under the proper runtime overflow test. This means
that we can identify such phi nodes as an induction, and the loop-vectorizer
can now vectorize such inductions, however inefficiently. The vectorizer
doesn't know that it can ignore the casts, and so it vectorizes them.
This patch records the casts in the InductionDescriptor, so that they could
be marked to be ignored for cost calculation (we use VecValuesToIgnore for
that) and ignored for vectorization/widening/scalarization (i.e. treated as
TriviallyDead).
In addition to marking all these casts to be ignored, we also need to make
sure that each cast is mapped to the right vector value in the vector loop body
(be it a widened, vectorized, or scalarized induction). So whenever an
induction phi is mapped to a vector value (during vectorization/widening/
scalarization), we also map the respective cast instruction (if exists) to that
vector value. (If the phi-update sequence of an induction involves more than one
cast, then the above mapping to vector value is relevant only for the last cast
of the sequence as we allow only the "last cast" to be used outside the
induction update chain itself).
This is the last step in addressing PR30654.
llvm-svn: 320672
CreateAddRecFromPHIWithCastsImpl() adds an IncrementNUSW overflow predicate
which allows the PSCEV rewriter to rewrite this scev expression:
(zext i8 {0, + , (trunc i32 step to i8)} to i32)
into
{0, +, (sext i8 (trunc i32 step to i8) to i32)}
But then it adds the wrong Equal predicate:
%step == (zext i8 (trunc i32 %step to i8) to i32).
instead of:
%step == (sext i8 (trunc i32 %step to i8) to i32)
This is fixed here.
Differential Revision: https://reviews.llvm.org/D40641
llvm-svn: 320298
In this method, we invoke `SimplifyICmpOperands` which takes the `Cond` predicate
by reference and may change it along with `LHS` and `RHS` SCEVs. But then we invoke
`computeShiftCompareExitLimit` with Values from which the SCEVs have been derived,
these Values have not been modified while `Cond` could be.
One of possible outcomes of this is that we may falsely prove that an infinite loop ends
within some finite number of iterations.
In this patch, we save the original `Cond` and pass it along with original operands.
This logic may be removed in future once `computeShiftCompareExitLimit` works
with SCEVs instead of value operands.
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D40953
llvm-svn: 320142
Lexicographical comparison of SCEV trees is potentially expensive for big
expression trees. We can define ordering between them for AddRecs and
N-ary operations by SCEV NoWrap flags to make non-equality check
cheaper.
This change does not prevent grouping eqivalent SCEVs together and is
not supposed to have any meaningful impact on behavior of any transforms.
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D40645
llvm-svn: 319889
Current implementation of `compareSCEVComplexity` is being unreasonable with `SCEVUnknown`s:
every time it sees one, it creates a new value cache and tries to prove equality of two values using it.
This cache reallocates and gets lost from SCEV to SCEV.
This patch changes this behavior: now we create one cache for all values and share it between SCEVs.
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D40597
llvm-svn: 319880
Summary:
I don't think rL309080 is the right fix for PR33494 -- caching ExitLimit only
hides the problem[0]. The real issue is that because of how we forget SCEV
expressions ScalarEvolution::getBackedgeTakenInfo, in the test case for PR33494
computing the backedge for any loop invalidates the trip count for every other
loop. This effectively makes the SCEV cache useless.
I've instead made the SCEV expression invalidation in
ScalarEvolution::getBackedgeTakenInfo less aggressive to fix this issue.
[0]: One way to think about this is that rL309080 essentially augmented the
backedge-taken-count cache with another equivalent exit-limit cache. The bug
went away because we were explicitly not clearing the exit-limit cache in
getBackedgeTakenInfo. But instead of doing all of that, we can just avoid
clearing the backedge-taken-count cache.
Reviewers: mkazantsev, mzolotukhin
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D39361
llvm-svn: 319678
These command line options are not intended for public use, and often
don't even make sense in the context of a particular tool anyway. About
90% of them are already hidden, but when people add new options they
forget to hide them, so if you were to make a brand new tool today, link
against one of LLVM's libraries, and run tool -help you would get a
bunch of junk that doesn't make sense for the tool you're writing.
This patch hides these options. The real solution is to not have
libraries defining command line options, but that's a much larger effort
and not something I'm prepared to take on.
Differential Revision: https://reviews.llvm.org/D40674
llvm-svn: 319505
Currently, we use a set of pairs to cache responces like `CompareValueComplexity(X, Y) == 0`. If we had
proved that `CompareValueComplexity(S1, S2) == 0` and `CompareValueComplexity(S2, S3) == 0`,
this cache does not allow us to prove that `CompareValueComplexity(S1, S3)` is also `0`.
This patch replaces this set with `EquivalenceClasses` that merges Values into equivalence sets so that
any two values from the same set are equal from point of `CompareValueComplexity`. This, in particular,
allows us to prove the fact from example above.
Differential Revision: https://reviews.llvm.org/D40429
llvm-svn: 319153
Currently, we use a set of pairs to cache responces like `CompareSCEVComplexity(X, Y) == 0`. If we had
proved that `CompareSCEVComplexity(S1, S2) == 0` and `CompareSCEVComplexity(S2, S3) == 0`,
this cache does not allow us to prove that `CompareSCEVComplexity(S1, S3)` is also `0`.
This patch replaces this set with `EquivalenceClasses` any two values from the same set are equal from
point of `CompareSCEVComplexity`. This, in particular, allows us to prove the fact from example above.
Differential Revision: https://reviews.llvm.org/D40428
llvm-svn: 319149
Summary:
For a given loop, getLoopLatch returns a non-null value
when a loop has only one latch block. In the modified
context adding an assertion to check that both the outgoing branches of
a terminator instruction (of latch) does not target same header.
+
few minor code reorganization.
Reviewers: jbhateja
Reviewed By: jbhateja
Subscribers: sanjoy
Differential Revision: https://reviews.llvm.org/D40460
llvm-svn: 318997
Summary:
For a given loop, getLoopLatch returns a non-null value
when a loop has only one latch block. In the modified
context a check on both the outgoing branches of a terminator instruction (of latch) to same header is redundant.
Reviewers: jbhateja
Reviewed By: jbhateja
Subscribers: sanjoy
Differential Revision: https://reviews.llvm.org/D40460
llvm-svn: 318991
Given loops `L1` and `L2` with AddRecs `AR1` and `AR2` varying in them respectively.
When identifying loop disposition of `AR2` w.r.t. `L1`, we only say that it is varying if
`L1` contains `L2`. But there is also a possible situation where `L1` and `L2` are
consecutive sibling loops within the parent loop. In this case, `AR2` is also varying
w.r.t. `L1`, but we don't correctly identify it.
It can lead, for exaple, to attempt of incorrect folding. Consider:
AR1 = {a,+,b}<L1>
AR2 = {c,+,d}<L2>
EXAR2 = sext(AR1)
MUL = mul AR1, EXAR2
If we incorrectly assume that `EXAR2` is invariant w.r.t. `L1`, we can end up trying to
construct something like: `{a * {c,+,d}<L2>,+,b * {c,+,d}<L2>}<L1>`, which is incorrect
because `AR2` is not available on entrance of `L1`.
Both situations "`L1` contains `L2`" and "`L1` preceeds sibling loop `L2`" can be handled
with one check: "header of `L1` dominates header of `L2`". This patch replaces the old
insufficient check with this one.
Differential Revision: https://reviews.llvm.org/D39453
llvm-svn: 318819
I don't believe this was a problem in practice, as it's likely that the
boolean wasn't checked unless the backend condition was non-null.
llvm-svn: 318073
Summary:
If a compare instruction is same or inverse of the compare in the
branch of the loop latch, then return a constant evolution node.
This shall facilitate computations of loop exit counts in cases
where compare appears in the evolution chain of induction variables.
Will fix PR 34538
Reviewers: sanjoy, hfinkel, junryoungju
Reviewed By: sanjoy, junryoungju
Subscribers: javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D38494
llvm-svn: 318050
Max backedge taken count is always expected to be a constant; and this is
usually true by construction -- it is a SCEV expression with constant inputs.
However, if the max backedge expression ends up being computed to be a udiv with
a constant zero denominator[0], SCEV does not fold the result to a constant
since there is no constant it can fold it to (SCEV has no representation for
"infinity" or "undef").
However, in computeMaxBECountForLT we already know the denominator is positive,
and thus at least 1; and we can use this fact to avoid dividing by zero.
[0]: We can end up with a constant zero denominator if the signed range of the
stride is more precise than the unsigned range.
llvm-svn: 316615
Summary:
If a compare instruction is same or inverse of the compare in the
branch of the loop latch, then return a constant evolution node.
Currently scope of evaluation is limited to SCEV computation for
PHI nodes.
This shall facilitate computations of loop exit counts in cases
where compare appears in the evolution chain of induction variables.
Will fix PR 34538
Reviewers: sanjoy, hfinkel, junryoungju
Reviewed By: junryoungju
Subscribers: javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D38494
llvm-svn: 316054
This reverts commit r315713. It causes PR34968.
I think I know what the problem is, but I don't think I'll have time to fix it
this week.
llvm-svn: 315962
Summary:
This change uses the loop use list added in the previous change to remember the
loops that appear in the trip count expressions of other loops; and uses it in
forgetLoop. This lets us not scan every loop in the function on a forgetLoop
call.
With this change we no longer invalidate clear out backedge taken counts on
forgetValue. I think this is fine -- the contract is that SCEV users must call
forgetLoop(L) if their change to the IR could have changed the trip count of L;
solely calling forgetValue on a value feeding into the backedge condition of L
is not enough. Moreover, I don't think we can strengthen forgetValue to be
sufficient for invalidating trip counts without significantly re-architecting
SCEV. For instance, if we have the loop:
I = *Ptr;
E = I + 10;
do {
// ...
} while (++I != E);
then the backedge taken count of the loop is 9, and it has no reference to
either I or E, i.e. there is no way in SCEV today to re-discover the dependency
of the loop's trip count on E or I. So a SCEV client cannot change E to (say)
"I + 20", call forgetValue(E) and expect the loop's trip count to be updated.
Reviewers: atrick, sunfish, mkazantsev
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D38435
llvm-svn: 315713
Summary:
This patch teaches SCEV to calculate the maxBECount when the end bound
of the loop can vary. Note that we cannot calculate the exactBECount.
This will only be done when both conditions are satisfied:
1. the loop termination condition is strictly LT.
2. the IV is proven to not overflow.
This provides more information to users of SCEV and can be used to
improve identification of finite loops.
Reviewers: sanjoy, mkazantsev, silviu.baranga, atrick
Reviewed by: mkazantsev
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38825
llvm-svn: 315683
Summary:
Currently we do not correctly invalidate memoized results for add recurrences
that were created directly (i.e. they were not created from a `Value`). This
change fixes this by keeping loop use lists and using the loop use lists to
determine which SCEV expressions to invalidate.
Here are some statistics on the number of uses of in the use lists of all loops
on a clang bootstrap (config: release, no asserts):
Count: 731310
Min: 1
Mean: 8.555150
50th %time: 4
95th %tile: 25
99th %tile: 53
Max: 433
Reviewers: atrick, sunfish, mkazantsev
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D38434
llvm-svn: 315672
Summary:
Add LLVM_FORCE_ENABLE_DUMP cmake option, and use it along with
LLVM_ENABLE_ASSERTIONS to set LLVM_ENABLE_DUMP.
Remove NDEBUG and only use LLVM_ENABLE_DUMP to enable dump methods.
Move definition of LLVM_ENABLE_DUMP from config.h to llvm-config.h so
it'll be picked up by public headers.
Differential Revision: https://reviews.llvm.org/D38406
llvm-svn: 315590
Summary:
This patch fixes an error in the patch to ScalarEvolution::createAddRecFromPHIWithCastsImpl
made in D37265. In that patch we handle the cases where the either the start or accum values can be
zero after truncation. But, we assume that the start value must be a constant if the accum is
zero. This is clearly an erroneous assumption. This change removes that assumption.
Reviewers: sanjoy, dorit, mkazantsev
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38814
llvm-svn: 315491
Summary:
A SCEV such as:
{%v2,+,((-1 * (trunc i64 (-1 * %v1) to i32)) + (-1 * (trunc i64 %v1 to i32)))}<%loop>
can be folded into, simply, {%v2,+,0}. However, the current code in ::getAddExpr()
will not try to apply the simplification m*trunc(x)+n*trunc(y) -> trunc(trunc(m)*x+trunc(n)*y)
because it only keys off having a non-multiplied trunc as the first term in the simplification.
This patch generalizes this code to try to do a more generic fold of these trunc
expressions.
Reviewers: sanjoy
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D37888
llvm-svn: 313988
forgetLoop() has pretty bad performance because it goes over
the same instructions over and over again in particular when
nested loop are involved.
The refactoring changes the function to a not-recursive function
and reusing the allocation for data-structures and the Visited
set.
NFCI
Differential Revision: https://reviews.llvm.org/D37659
llvm-svn: 312920
Summary:
When constructing the predicate P1 in ScalarEvolution::createAddRecFromPHIWithCastsImpl() it is possible
for the PHISCEV from which the predicate is constructed to be a SCEVConstant instead of a SCEVAddRec. If
this happens, then the cast<SCEVAddRec>(PHISCEV) in the code will assert.
Such a PHISCEV is possible if either the start value or the accumulator value is a constant value
that not equal to its truncated value, and if the truncated value is zero.
This patch adds tests that demonstrate the cast<> assertion, and fixes this problem by checking
whether the PHISCEV is a constant before constructing the P1 predicate; if it is, then P1 is
equivalent to one of P2 or P3. Additionally, if we know that the start value or accumulator
value are constants then we check whether the P2 and/or P3 predicates are known false at compile
time; if either is, then we bail out of constructing the AddRec.
Reviewers: sanjoy, mkazantsev, silviu.baranga
Reviewed By: mkazantsev
Subscribers: mkazantsev, llvm-commits
Differential Revision: https://reviews.llvm.org/D37265
llvm-svn: 312568
In LLVM IR the following code:
%r = urem <ty> %t, %b
is equivalent to
%q = udiv <ty> %t, %b
%s = mul <ty> nuw %q, %b
%r = sub <ty> nuw %t, %q ; (t / b) * b + (t % b) = t
As UDiv, Mul and Sub are already supported by SCEV, URem can be implemented
with minimal effort using that relation:
%r --> (-%b * (%t /u %b)) + %t
We implement two special cases:
- if %b is 1, the result is always 0
- if %b is a power-of-two, we produce a zext/trunc based expression instead
That is, the following code:
%r = urem i32 %t, 65536
Produces:
%r --> (zext i16 (trunc i32 %a to i16) to i32)
Note that while this helps get a tighter bound on the range analysis and the
known-bits analysis, this exposes some normalization shortcoming of SCEVs:
%div = udim i32 %a, 65536
%mul = mul i32 %div, 65536
%rem = urem i32 %a, 65536
%add = add i32 %mul, %rem
Will usually not be reduced.
llvm-svn: 312329
Pushes the sext onto the operands of a Sub if NSW is present.
Also adds support for propagating the nowrap flags of the
llvm.ssub.with.overflow intrinsic during analysis.
Differential Revision: https://reviews.llvm.org/D35256
llvm-svn: 310117
The patch rL309080 was reverted because it did not clean up the cache on "forgetValue"
method call. This patch re-enables this change, adds the missing check and introduces
two new unit tests that make sure that the cache is cleaned properly.
Differential Revision: https://reviews.llvm.org/D36087
llvm-svn: 309925
If SCEV can prove that the backedge taken count for a loop is zero, it does not
need to "understand" a recursive PHI to compute its exiting value.
This should fix PR33885.
llvm-svn: 309758
This patch reworks the function that searches constants in Add and Mul SCEV expression
chains so that now it does not visit a node more than once, and also renames this function
for better correspondence between its implementation and semantics.
Differential Revision: https://reviews.llvm.org/D35931
llvm-svn: 309367
This reverts commit r309080. The patch needs to clear out the
ScalarEvolution::ExitLimits cache in forgetMemoizedResults.
I've replied on the commit thread for the patch with more details.
llvm-svn: 309357
This patch adds a cache for computeExitLimit to save compilation time. A lot of examples of
tests that take extensive time to compile are attached to the bug 33494.
Differential Revision: https://reviews.llvm.org/D35827
llvm-svn: 309080
`SCEVUnknown::allUsesReplacedWith` does not need to call `forgetMemoizedResults`
since RAUW does a value-equivalent replacement by assumption. If this
assumption was false then the later setValPtr(New) call would be incorrect too.
This is a non-trivial performance optimization for functions with a large number
of loops since `forgetMemoizedResults` walks all loop backedge taken counts to
see if any of them use the SCEVUnknown being RAUWed. However, this improvement
is difficult to demonstrate without checking in an excessively large IR file.
llvm-svn: 309072
When SCEV calculates product of two SCEVAddRecs from the same loop, it
tries to combine them into one big AddRecExpr. If the sizes of the initial
SCEVs were `S1` and `S2`, the size of their product is `S1 + S2 - 1`, and every
operand of the resulting SCEV is combined from operands of initial SCEV and
has much higher complexity than they have.
As result, if we try to calculate something like:
%x1 = {a,+,b}
%x2 = mul i32 %x1, %x1
%x3 = mul i32 %x2, %x1
%x4 = mul i32 %x3, %x2
...
The size of such SCEVs grows as `2^N`, and the arguments
become more and more complex as we go forth. This leads
to long compilation and huge memory consumption.
This patch sets a limit after which we don't try to combine two
`SCEVAddRecExpr`s into one. By default, max allowed size of the
resulting AddRecExpr is set to 16.
Differential Revision: https://reviews.llvm.org/D35664
llvm-svn: 308847
using runtime checks
Extend the SCEVPredicateRewriter to work a bit harder when it encounters an
UnknownSCEV for a Phi node; Try to build an AddRecurrence also for Phi nodes
whose update chain involves casts that can be ignored under the proper runtime
overflow test. This is one step towards addressing PR30654.
Differential revision: http://reviews.llvm.org/D30041
llvm-svn: 308299
Going through the Constant methods requires redetermining that the Constant is a ConstantInt and then calling isZero/isOne/isMinusOne.
llvm-svn: 307292
In rL300494 there was an attempt to deal with excessive compile time on
invocations of getSign/ZeroExtExpr using local caching. This approach only
helps if we request the same SCEV multiple times throughout recursion. But
in the bug PR33431 we see a case where we request different values all the time,
so caching does not help and the size of the cache grows enormously.
In this patch we remove the local cache for this methods and add the recursion
depth limit instead, as we do for arithmetics. This gives us a guarantee that the
invocation sequence is limited and reasonably short.
Differential Revision: https://reviews.llvm.org/D34273
llvm-svn: 306785
In LLVM IR the following code:
%r = urem <ty> %t, %b
is equivalent to:
%q = udiv <ty> %t, %b
%s = mul <ty> nuw %q, %b
%r = sub <ty> nuw %t, %q ; (t / b) * b + (t % b) = t
As UDiv, Mul and Sub are already supported by SCEV, URem can be
implemented with minimal effort this way.
Note: While SRem and SDiv are also related this way, SCEV does not
provides SDiv yet.
llvm-svn: 306695
Summary:
This patch changes getRange to getRangeRef and returns a reference to the ConstantRange object stored inside the DenseMap caches. We then take advantage of that to add new helper methods that can return min/max value of a signed or unsigned ConstantRange using that reference without first copying the ConstantRange.
getRangeRef calls itself recursively and I believe the reference return is fine for those calls.
I've left getSignedRange and getUnsignedRange returning a ConstantRange object so they will make a copy now. This is to ensure safety since the reference will be invalidated if the DenseMap changes.
I'm sure there are still more places that can take advantage of the reference and I'll submit future patches as I find them.
Reviewers: sanjoy, davide
Reviewed By: sanjoy
Subscribers: zzheng, llvm-commits, mzolotukhin
Differential Revision: https://reviews.llvm.org/D32978
llvm-svn: 306229
MulOpsInlineThreshold option of SCEV is defaulted to 1000, which is inadequately high.
When constructing SCEVs of expressions like:
x1 = a * a
x2 = x1 * x1
x3 = x2 * x2
...
We actually have huge SCEVs with max allowed amount of operands inlined.
Such expressions are easy to get from unrolling of loops looking like
x = a
for (i = 0; i < n; i++)
x = x * x
Or more tricky cases where big powers are involved. If some non-linear analysis
tries to work with a SCEV that has 1000 operands, it may lead to excessively long
compilation. The attached test does not pass within 1 minute with default threshold.
This patch decreases its default value to 32, which looks much more reasonable if we
use analyzes with complexity O(N^2) or O(N^3) working with SCEV.
Differential Revision: https://reviews.llvm.org/D34397
llvm-svn: 305882
The description of this option was copy-pasted from another one and does not
correspond to reality.
Differential Revision: https://reviews.llvm.org/D34390
llvm-svn: 305782
This is a fix for PR33292 that shows a case of extremely long compilation
of a single .c file with clang, with most time spent within SCEV.
We have a mechanism of limiting recursion depth for getAddExpr to avoid
long analysis in SCEV. However, there are calls from getAddExpr to getMulExpr
and back that do not propagate the info about depth. As result of this, a chain
getAddExpr -> ... .> getAddExpr -> getMulExpr -> getAddExpr -> ... -> getAddExpr
can be extremely long, with every segment of getAddExpr's being up to max depth long.
This leads either to long compilation or crash by stack overflow. We face this situation while
analyzing big SCEVs in the test of PR33292.
This patch applies the same limit on max expression depth for getAddExpr and getMulExpr.
Differential Revision: https://reviews.llvm.org/D33984
llvm-svn: 305463
I did this a long time ago with a janky python script, but now
clang-format has built-in support for this. I fed clang-format every
line with a #include and let it re-sort things according to the precise
LLVM rules for include ordering baked into clang-format these days.
I've reverted a number of files where the results of sorting includes
isn't healthy. Either places where we have legacy code relying on
particular include ordering (where possible, I'll fix these separately)
or where we have particular formatting around #include lines that
I didn't want to disturb in this patch.
This patch is *entirely* mechanical. If you get merge conflicts or
anything, just ignore the changes in this patch and run clang-format
over your #include lines in the files.
Sorry for any noise here, but it is important to keep these things
stable. I was seeing an increasing number of patches with irrelevant
re-ordering of #include lines because clang-format was used. This patch
at least isolates that churn, makes it easy to skip when resolving
conflicts, and gets us to a clean baseline (again).
llvm-svn: 304787
Max Kazantsev