This adjusts the description of `llvm.memcpy` to also allow operands
to be equal. This is in line with what Clang currently expects.
This change is intended to be temporary and followed by re-introduce
a variant with the non-overlapping guarantee for cases where we can
actually ensure that property in the front-end.
See the links below for more details:
http://lists.llvm.org/pipermail/cfe-dev/2020-August/066614.html
and PR11763.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D86815
Some tests from multibuild-malloc-free.ll do not actually use malloc or
free and where split out to multiblock-throwing.ll, but not removed from
the original file. This patch cleans that up. It also moves @test22 to
simple.ll, because it does not involve multiple blocks.
This patch moves the tests for the old MemDepAnalysis based DSE
implementation to the MemDepAnalysis subdirectory and updates them to
pass -enable-dse-memoryssa=false.
This is in preparation for the switch to MemorySSA-backed DSE.
This changes getDomMemoryDef to check if a Current is a valid
candidate for elimination before checking for reads. Before the change,
we were spending a lot of compile-time in checking for read accesses for
Current that might not even be removable.
This patch flips the logic, so we skip Current if they cannot be
removed before checking all their uses. This is much more efficient in
practice.
It also adds a more aggressive limit for checking partially overlapping
stores. The main problem with overlapping stores is that we do not know
if they will lead to elimination until seeing all of them. This patch
limits adds a new limit for overlapping store candidates, which keeps
the number of modified overlapping stores roughly the same.
This is another substantial compile-time improvement (while also
increasing the number of stores eliminated). Geomean -O3 -0.67%,
ReleaseThinLTO -0.97%.
http://llvm-compile-time-tracker.com/compare.php?from=0a929b6978a068af8ddb02d0d4714a2843dd8ba9&to=2e630629b43f64b60b282e90f0d96082fde2dacc&stat=instructions
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D86487
This patch adds support for memcmp in MemoryLocation::getForArgument.
memcmp reads from the first 2 arguments up to the number of bytes of the
third argument.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D86725
For DSE with MemorySSA it is beneficial to manually traverse the
defining access, instead of using a MemorySSA walker, so we can
better control the number of steps together with other limits and
also weed out invalid/unprofitable paths early on.
This patch requires a follow-up patch to be most effective, which I will
share soon after putting this patch up.
This temporarily XFAIL's the limit tests, because we now explore more
MemoryDefs that may not alias/clobber the killing def. This will be
improved/fixed by the follow-up patch.
This patch also renames some `Dom*` variables to `Earlier*`, because the
dominance relation is not really used/important here and potentially
confusing.
This patch allows us to aggressively cut down compile time, geomean
-O3 -0.64%, ReleaseThinLTO -1.65%, at the expense of fewer stores
removed. Subsequent patches will increase the number of removed stores
again, while keeping compile-time in check.
http://llvm-compile-time-tracker.com/compare.php?from=d8e3294118a8c5f3f97688a704d5a05b67646012&to=0a929b6978a068af8ddb02d0d4714a2843dd8ba9&stat=instructions
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D86486
Avoid computing InvisibleToCallerBefore/AfterRet up front. In most
cases, this information is not really needed. Instead, introduce helper
functions to compute and cache the result on demand.
Notably, this also does not use PointerMayBeCapturedBefore for
isInvisibleToCallerBeforeRet, as it requires the killing MemoryDef as
starting instruction, making the caching ineffective. But it appears the
use of PointerMayBeCapturedBefore has very limited benefits in practice
(e.g. on SPEC2000/SPEC2006/MultiSource there are no binary changes with
-O3 -flto). Refrain from using it for now, to limit-compile-time.
This gives some nice compile-time improvements:
http://llvm-compile-time-tracker.com/compare.php?from=db9345f6810f379a36752dc52caf5230585d0ebd&to=b4d091047e1b8a3d377d200137b79d03aca65663&stat=instructions
Limit elimination of stores at the end of a function to MemoryDefs with
a single underlying object, to save compile time.
In practice, the case with multiple underlying objects seems not very
important in practice. For -O3 -flto on MultiSource/SPEC2000/SPEC2006
this results in a total of 2 more stores being eliminated.
We can always re-visit that in the future.
Currently the code does not account for the fact that getDomMemoryDef
can be called with ScanLimit == 0, if we reached the limit while
processing an earlier access. Also tighten the check a bit more and bump
the scan limit now that it is handled properly.
In some cases, this brings a 2x speedup in terms of compile-time.
We are re-using tryToMergePartialOverlappingStores, which requires
earlier to domiante Later. In the long run,
tryToMergeParialOverlappingStores should be re-written using MemorySSA.
Fixes PR46513.
This fixes an instance where MemorySSA-using Dead Store Elimination is failing
to do a transformation that the non-MemorySSA-using version does.
Differential Revision: https://reviews.llvm.org/D83783
This patch adds support for eliminating stores by free & lifetime.end
calls. We can remove stores that are not read before calling a memory
terminator and we can eliminate all stores after a memory terminator
until we see a new lifetime.start. The second case seems to not really
trigger much in practice though.
Reviewers: dmgreen, rnk, efriedma, bryant, asbirlea, Tyker
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D72410
This patch add support for eliminating MemoryDefs that do not have any
aliasing users, which indicates that there are no reads/writes to the
memory location until the end of the function.
To eliminate such defs, we have to ensure that the underlying object is
not visible in the caller and does not escape via returning. We need a
separate check for that, as InvisibleToCaller does not consider returns.
Reviewers: dmgreen, rnk, efriedma, bryant, asbirlea, Tyker, george.burgess.iv
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D72631
This patch extends storeIsNoop to also detect stores of 0 to an calloced
object. This basically ports the logic from legacy DSE to the MemorySSA
backed version.
It triggers in a few cases on MultiSource, SPEC2000, SPEC2006 with -O3
LTO:
Same hash: 218 (filtered out)
Remaining: 19
Metric: dse.NumNoopStores
Program base patch2 diff
test-suite...CFP2000/177.mesa/177.mesa.test 1.00 15.00 1400.0%
test-suite...6/482.sphinx3/482.sphinx3.test 1.00 14.00 1300.0%
test-suite...lications/ClamAV/clamscan.test 2.00 28.00 1300.0%
test-suite...CFP2006/433.milc/433.milc.test 1.00 8.00 700.0%
test-suite...pplications/oggenc/oggenc.test 2.00 9.00 350.0%
test-suite.../CINT2000/176.gcc/176.gcc.test 6.00 6.00 0.0%
test-suite.../CINT2006/403.gcc/403.gcc.test NaN 137.00 nan%
test-suite...libquantum/462.libquantum.test NaN 3.00 nan%
test-suite...6/464.h264ref/464.h264ref.test NaN 7.00 nan%
test-suite...decode/alacconvert-decode.test NaN 2.00 nan%
test-suite...encode/alacconvert-encode.test NaN 2.00 nan%
test-suite...ications/JM/ldecod/ldecod.test NaN 9.00 nan%
test-suite...ications/JM/lencod/lencod.test NaN 39.00 nan%
test-suite.../Applications/lemon/lemon.test NaN 2.00 nan%
test-suite...pplications/treecc/treecc.test NaN 4.00 nan%
test-suite...hmarks/McCat/08-main/main.test NaN 4.00 nan%
test-suite...nsumer-lame/consumer-lame.test NaN 3.00 nan%
test-suite.../Prolangs-C/bison/mybison.test NaN 1.00 nan%
test-suite...arks/mafft/pairlocalalign.test NaN 30.00 nan%
Reviewers: efriedma, zoecarver, asbirlea
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D82204
Currently we stop exploring candidates too early in some cases.
In particular, we can continue checking the defining accesses of
non-removable MemoryDefs and defs without analyzable write location
(read clobbers are already ruled out using MemorySSA at this point).
As we traverse the CFG backwards, we could end up reaching unreachable
blocks. For unreachable blocks, we won't have computed post order
numbers and because DomAccess is reachable, unreachable blocks cannot be
on any path from it.
This fixes a crash with unreachable blocks.
All cases in the test are supported now, it only still failed because an
over-eager regex match not accounting for `, align ` being added to each
load/store now.
Port partial constant store merging logic to MemorySSA backed DSE. The
heavy lifting is done by the existing helper function. It is used in
context where we already ensured that the later instruction can
eliminate the earlier one, if it is a complete overwrite.
isOverwrite expects the later location as first argument and the earlier
result later. The adjusted call is intended to check whether CC
overwrites DefLoc.
This patch relaxes the post-dominance requirement for accesses to
objects visible after the function returns.
Instead of requiring the killing def to post-dominate the access to
eliminate, the set of 'killing blocks' (= blocks that completely
overwrite the original access) is collected.
If all paths from the access to eliminate and an exit block go through a
killing block, the access can be removed.
To check this property, we first get the common post-dominator block for
the killing blocks. If this block does not post-dominate the access
block, there may be a path from DomAccess to an exit block not involving
any killing block.
Otherwise we have to check if there is a path from the DomAccess to the
common post-dominator, that does not contain a killing block. If there
is no such path, we can remove DomAccess. For this check, we start at
the common post-dominator and then traverse the CFG backwards. Paths are
terminated when we hit a killing block or a block that is not executed
between DomAccess and a killing block according to the post-order
numbering (if the post order number of a block is greater than the one
of DomAccess, the block cannot be in in a path starting at DomAccess).
This gives the following improvements on the total number of stores
after DSE for MultiSource, SPEC2K, SPEC2006:
Tests: 237
Same hash: 206 (filtered out)
Remaining: 31
Metric: dse.NumRemainingStores
Program base new100 diff
test-suite...CFP2000/188.ammp/188.ammp.test 3624.00 3544.00 -2.2%
test-suite...ch/g721/g721encode/encode.test 128.00 126.00 -1.6%
test-suite.../Benchmarks/Olden/mst/mst.test 73.00 72.00 -1.4%
test-suite...CFP2006/433.milc/433.milc.test 3202.00 3163.00 -1.2%
test-suite...000/186.crafty/186.crafty.test 5062.00 5010.00 -1.0%
test-suite...-typeset/consumer-typeset.test 40460.00 40248.00 -0.5%
test-suite...Source/Benchmarks/sim/sim.test 642.00 639.00 -0.5%
test-suite...nchmarks/McCat/09-vor/vor.test 642.00 644.00 0.3%
test-suite...lications/sqlite3/sqlite3.test 35664.00 35563.00 -0.3%
test-suite...T2000/300.twolf/300.twolf.test 7202.00 7184.00 -0.2%
test-suite...lications/ClamAV/clamscan.test 19475.00 19444.00 -0.2%
test-suite...INT2000/164.gzip/164.gzip.test 2199.00 2196.00 -0.1%
test-suite...peg2/mpeg2dec/mpeg2decode.test 2380.00 2378.00 -0.1%
test-suite.../Benchmarks/Bullet/bullet.test 39335.00 39309.00 -0.1%
test-suite...:: External/Povray/povray.test 36951.00 36927.00 -0.1%
test-suite...marks/7zip/7zip-benchmark.test 67396.00 67356.00 -0.1%
test-suite...6/464.h264ref/464.h264ref.test 31497.00 31481.00 -0.1%
test-suite...006/453.povray/453.povray.test 51441.00 51416.00 -0.0%
test-suite...T2006/401.bzip2/401.bzip2.test 4450.00 4448.00 -0.0%
test-suite...Applications/kimwitu++/kc.test 23481.00 23471.00 -0.0%
test-suite...chmarks/MallocBench/gs/gs.test 6286.00 6284.00 -0.0%
test-suite.../CINT2000/254.gap/254.gap.test 13719.00 13715.00 -0.0%
test-suite.../Applications/SPASS/SPASS.test 30345.00 30338.00 -0.0%
test-suite...006/450.soplex/450.soplex.test 15018.00 15016.00 -0.0%
test-suite...ications/JM/lencod/lencod.test 27780.00 27777.00 -0.0%
test-suite.../CINT2006/403.gcc/403.gcc.test 105285.00 105276.00 -0.0%
There might be potential to pre-compute some of the information of which
blocks are on the path to an exit for each block, but the overall
benefit might be comparatively small.
On the set of benchmarks, 15738 times out of 20322 we reach the
CFG check, the CFG check is successful. The total number of iterations
in the CFG check is 187810, so on average we need less than 10 steps in
the check loop. Bumping the threshold in the loop from 50 to 150 gives a
few small improvements, but I don't think they warrant such a big bump
at the moment. This is all pending further tuning in the future.
Reviewers: dmgreen, bryant, asbirlea, Tyker, efriedma, george.burgess.iv
Reviewed By: george.burgess.iv
Differential Revision: https://reviews.llvm.org/D78932
See https://reviews.llvm.org/D74651 for the preallocated IR constructs
and LangRef changes.
In X86TargetLowering::LowerCall(), if a call is preallocated, record
each argument's offset from the stack pointer and the total stack
adjustment. Associate the call Value with an integer index. Store the
info in X86MachineFunctionInfo with the integer index as the key.
This adds two new target independent ISDOpcodes and two new target
dependent Opcodes corresponding to @llvm.call.preallocated.{setup,arg}.
The setup ISelDAG node takes in a chain and outputs a chain and a
SrcValue of the preallocated call Value. It is lowered to a target
dependent node with the SrcValue replaced with the integer index key by
looking in X86MachineFunctionInfo. In
X86TargetLowering::EmitInstrWithCustomInserter() this is lowered to an
%esp adjustment, the exact amount determined by looking in
X86MachineFunctionInfo with the integer index key.
The arg ISelDAG node takes in a chain, a SrcValue of the preallocated
call Value, and the arg index int constant. It produces a chain and the
pointer fo the arg. It is lowered to a target dependent node with the
SrcValue replaced with the integer index key by looking in
X86MachineFunctionInfo. In
X86TargetLowering::EmitInstrWithCustomInserter() this is lowered to a
lea of the stack pointer plus an offset determined by looking in
X86MachineFunctionInfo with the integer index key.
Force any function containing a preallocated call to use the frame
pointer.
Does not yet handle a setup without a call, or a conditional call.
Does not yet handle musttail. That requires a LangRef change first.
Tried to look at all references to inalloca and see if they apply to
preallocated. I've made preallocated versions of tests testing inalloca
whenever possible and when they make sense (e.g. not alloca related,
inalloca edge cases).
Aside from the tests added here, I checked that this codegen produces
correct code for something like
```
struct A {
A();
A(A&&);
~A();
};
void bar() {
foo(foo(foo(foo(foo(A(), 4), 5), 6), 7), 8);
}
```
by replacing the inalloca version of the .ll file with the appropriate
preallocated code. Running the executable produces the same results as
using the current inalloca implementation.
Reverted due to unexpectedly passing tests, added REQUIRES: asserts for reland.
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D77689
See https://reviews.llvm.org/D74651 for the preallocated IR constructs
and LangRef changes.
In X86TargetLowering::LowerCall(), if a call is preallocated, record
each argument's offset from the stack pointer and the total stack
adjustment. Associate the call Value with an integer index. Store the
info in X86MachineFunctionInfo with the integer index as the key.
This adds two new target independent ISDOpcodes and two new target
dependent Opcodes corresponding to @llvm.call.preallocated.{setup,arg}.
The setup ISelDAG node takes in a chain and outputs a chain and a
SrcValue of the preallocated call Value. It is lowered to a target
dependent node with the SrcValue replaced with the integer index key by
looking in X86MachineFunctionInfo. In
X86TargetLowering::EmitInstrWithCustomInserter() this is lowered to an
%esp adjustment, the exact amount determined by looking in
X86MachineFunctionInfo with the integer index key.
The arg ISelDAG node takes in a chain, a SrcValue of the preallocated
call Value, and the arg index int constant. It produces a chain and the
pointer fo the arg. It is lowered to a target dependent node with the
SrcValue replaced with the integer index key by looking in
X86MachineFunctionInfo. In
X86TargetLowering::EmitInstrWithCustomInserter() this is lowered to a
lea of the stack pointer plus an offset determined by looking in
X86MachineFunctionInfo with the integer index key.
Force any function containing a preallocated call to use the frame
pointer.
Does not yet handle a setup without a call, or a conditional call.
Does not yet handle musttail. That requires a LangRef change first.
Tried to look at all references to inalloca and see if they apply to
preallocated. I've made preallocated versions of tests testing inalloca
whenever possible and when they make sense (e.g. not alloca related,
inalloca edge cases).
Aside from the tests added here, I checked that this codegen produces
correct code for something like
```
struct A {
A();
A(A&&);
~A();
};
void bar() {
foo(foo(foo(foo(foo(A(), 4), 5), 6), 7), 8);
}
```
by replacing the inalloca version of the .ll file with the appropriate
preallocated code. Running the executable produces the same results as
using the current inalloca implementation.
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D77689
This is D77454, except for stores. All the infrastructure work was done
for loads, so the remaining changes necessary are relatively small.
Differential Revision: https://reviews.llvm.org/D79968
For IR generated by a compiler, this is really simple: you just take the
datalayout from the beginning of the file, and apply it to all the IR
later in the file. For optimization testcases that don't care about the
datalayout, this is also really simple: we just use the default
datalayout.
The complexity here comes from the fact that some LLVM tools allow
overriding the datalayout: some tools have an explicit flag for this,
some tools will infer a datalayout based on the code generation target.
Supporting this properly required plumbing through a bunch of new
machinery: we want to allow overriding the datalayout after the
datalayout is parsed from the file, but before we use any information
from it. Therefore, IR/bitcode parsing now has a callback to allow tools
to compute the datalayout at the appropriate time.
Not sure if I covered all the LLVM tools that want to use the callback.
(clang? lli? Misc IR manipulation tools like llvm-link?). But this is at
least enough for all the LLVM regression tests, and IR without a
datalayout is not something frontends should generate.
This change had some sort of weird effects for certain CodeGen
regression tests: if the datalayout is overridden with a datalayout with
a different program or stack address space, we now parse IR based on the
overridden datalayout, instead of the one written in the file (or the
default one, if none is specified). This broke a few AVR tests, and one
AMDGPU test.
Outside the CodeGen tests I mentioned, the test changes are all just
fixing CHECK lines and moving around datalayout lines in weird places.
Differential Revision: https://reviews.llvm.org/D78403
Summary:
If the only use of a value is a start or end lifetime intrinsic then mark the intrinsic as trivially dead. This should allow for that value to then be removed as well.
Currently, this only works for allocas, globals, and arguments.
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D79355
Summary:
If the only use of a value is a start or end lifetime intrinsic then mark the intrinsic as trivially dead. This should allow for that value to then be removed as well.
Currently, this only works for allocas, globals, and arguments.
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D79355
Florian Hahn