With improved analysis in determining CFG equivalence that does
not require strict dominance and post-dominance conditions, we
now relax isSafeToMoveBefore() such that an instruction I can
be moved before InsertPoint even if they do not strictly dominate
each other, as long as they follow the same control flow path.
For example, we can move Instruction 0 before Instruction 1,
and vice versa.
```
if (cond1)
// Instruction 0: %add = add i32 1, 2
if (cond1)
// Instruction 1: %add2 = add i32 2, 1
```
Reviewed By: Whitney
Differential Revision: https://reviews.llvm.org/D110456
Thinlink provides an opportunity to propagate function attributes across modules, enabling additional propagation opportunities.
This change propagates (currently default off, turn on with `disable-thinlto-funcattrs=1`) noRecurse and noUnwind based off of function summaries of the prevailing functions in bottom-up call-graph order. Testing on clang self-build:
1. There's a 35-40% increase in noUnwind functions due to the additional propagation opportunities.
2. Throughput is measured at 10-15% increase in thinlink time which itself is 1.5% of E2E link time.
Implementation-wise this adds the following summary function attributes:
1. noUnwind: function is noUnwind
2. mayThrow: function contains a non-call instruction that `Instruction::mayThrow` returns true on (e.g. windows SEH instructions)
3. hasUnknownCall: function contains calls that don't make it into the summary call-graph thus should not be propagated from (e.g. indirect for now, could add no-opt functions as well)
Testing:
Clang self-build passes and 2nd stage build passes check-all
ninja check-all with newly added tests passing
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D36850
We see that it might otherwise do:
%10 = getelementptr {}**, <2 x {}***> %9, <2 x i32> <i32 10, i32 4>
%11 = bitcast <2 x {}***> %10 to <2 x i64*>
...
%27 = extractelement <2 x i64*> %11, i32 0
%28 = bitcast i64* %27 to <2 x i64>*
store <2 x i64> %22, <2 x i64>* %28, align 4, !tbaa !2
Which is an out-of-bounds store (the extractelement got offset 10
instead of offset 4 as intended). With the fix, we correctly generate
extractelement for i32 1 and generate correct code.
Differential Revision: https://reviews.llvm.org/D106613
This is no-functional-change-intended, but it hopefully makes things
slightly clearer and more efficient to have transforms that require
'shl' be called only from visitShl(). Further cleanup is possible.
This is another step towards trying to re-apply D110170
by eliminating conflicting transforms that cause infinite loops.
a47c8e40c7 was a previous patch in this direction.
The diffs here are mostly cosmetic, but intentional:
1. The existing code that would handle this pattern in FoldShiftByConstant()
is limited to 'shl' only now. The formatting change to IsLeftShift shows
that we could move several transforms into visitShl() directly for
efficiency because they are not common shift transforms.
2. The tests are regenerated to show new instruction names to prove that
we are getting (almost) identical logic results.
3. The one case where we differ ("trunc_sandwich_small_shift1") shows that
we now use a narrow 'and' instruction. Previously, we relied on another
transform to do that, but it is limited to legal types. That seems to
be a legacy constraint from when IR analysis and codegen were less robust.
https://alive2.llvm.org/ce/z/JxyGA4
declare void @llvm.assume(i1)
define i8 @src(i32 %x, i32 %c0, i8 %c1) {
; The sum of the shifts must not overflow the source width.
%z1 = zext i8 %c1 to i32
%sum = add i32 %c0, %z1
%ov = icmp ult i32 %sum, 32
call void @llvm.assume(i1 %ov)
%sh1 = lshr i32 %x, %c0
%tr = trunc i32 %sh1 to i8
%sh2 = lshr i8 %tr, %c1
ret i8 %sh2
}
define i8 @tgt(i32 %x, i32 %c0, i8 %c1) {
%z1 = zext i8 %c1 to i32
%sum = add i32 %c0, %z1
%maskc = lshr i8 -1, %c1
%s = lshr i32 %x, %sum
%t = trunc i32 %s to i8
%a = and i8 %t, %maskc
ret i8 %a
}
Function specialization was crashing on poison values and constexpr values.
The problem is that these values are not added to the solver, so it crashes
when a lookup is performed for these values. This fixes that by not
specialising on these values. For poison that is obvious, but for constexpr
this is a change in behaviour. Thus, in one way this is a bit of a stopgap, but
specialising on constexpr values wasn't done very intentionally, and need some
more work and tests if we wanted to support this.
As a follow up, we need to look if the solver should exit more gracefully and
return a "don't know", or that it should really support these constexprs.
This should fix PR51600 (https://bugs.llvm.org/show_bug.cgi?id=51600).
Differential Revision: https://reviews.llvm.org/D110529
As it contains a self-reference, the default copy/move ctors
would not be safe.
Move the DSEState::get() method into the ctor to make sure no move
occurs here even without NRVO.
This is a speculative fix for test failures on
llvm-clang-x86_64-expensive-checks-win.
This is another regression noted with the proposal to canonicalize
to the min/max intrinsics in D98152.
Here are Alive2 attempts to show correctness without specifying
exact constants:
https://alive2.llvm.org/ce/z/bvfCwh (smax)
https://alive2.llvm.org/ce/z/of7eqy (smin)
https://alive2.llvm.org/ce/z/2Xtxoh (umax)
https://alive2.llvm.org/ce/z/Rm4Ad8 (umin)
(if you comment out the assume and/or no-wrap, you should see failures)
The different output for the umin test is due to a fold added with
c4fc2cb5b2 :
// umin(x, 1) == zext(x != 0)
We probably want to adjust that, so it applies more generally
(umax --> sext or patterns where we can fold to select-of-constants).
Some folds that were ok when starting with cmp+select may increase
instruction count for the equivalent intrinsic, so we have to decide
if it's worth altering a min/max.
Differential Revision: https://reviews.llvm.org/D110038
This is a followup to D109844 (and alternative to D109907), which
integrates the new "earliest escape" tracking into AliasAnalysis.
This is done by replacing the pre-existing context-free capture
cache in AAQueryInfo with a replaceable (virtual) object with two
implementations: The SimpleCaptureInfo implements the previous
behavior (check whether object is captured at all), while
EarliestEscapeInfo implements the new behavior from DSE.
This combines the "earliest escape" analysis with the full power of
BasicAA: It subsumes the call handling from D109907, considers a
wider range of escape sources, and works with AA recursion. The
compile-time cost is slightly higher than with D109907.
Differential Revision: https://reviews.llvm.org/D110368
It is sufficient that the object has not been captured before the
load that produces the pointer we're loading. A capture after that
can not affect the already loaded pointer.
This is small part of D110368 applied separately.
Only the multi-use cases are changing here because there's
another fold that catches the simpler patterns.
But that other fold is the source of infinite loops when we
try to add D110170, so removing that is planned as a follow-up.
Attempt to show the general proof in Alive2:
https://alive2.llvm.org/ce/z/Ns1uS2
Note that the overshift fold-to-zero tests are not
currently handled by instsimplify. If they were, we
could assert that the shift amount sum is less than
the source bitwidth.
In ThinLTO for locals we normally compute the GUID from the name after
prepending the source path to get a unique global id. SamplePGO indirect
call profiles contain the target GUID without this uniquification,
however (unless compiling with -funique-internal-linkage-names).
In order to correctly handle the call edges added to the combined index
for these indirect calls, during importing and bitcode writing we
consult a map of original to full GUID to identify the actual callee.
However, for a large application this was consuming a lot of compile
time as we need to do this repeatedly (especially during importing where
we may traverse call edges multiple times).
To fix this implement a suggestion in one of the FIXME comments, and
actually modify the call edges during a single traversal after the index
is built to perform the fixups once. I combined this fixup with the dead
code analysis performed on the index in order to avoid adding an
additional walk of the index. The dead code analysis is the first
analysis performed on the index.
This reduced the time required for a large thin link with SamplePGO by
about 20%.
No new test added, but I confirmed that there are existing tests that
will fail when no fixup is performed.
Differential Revision: https://reviews.llvm.org/D110374
It seems the crashes we saw wasn't caused by this (see comments on the review).
> This is basically D108837 but for jump threading. Free instructions
> should be ignored for the threading decision. JumpThreading already
> skips some free instructions (like pointer bitcasts), but does not
> skip various free intrinsics -- in fact, it currently gives them a
> fairly large cost of 2.
>
> Differential Revision: https://reviews.llvm.org/D110290
This reverts commit 4604695d7c.
This reverts the revert commit df56fc6ebb.
This version of the patch adjusts the location where the EarliestEscapes
cache is cleared when an instruction gets removed. The earliest escaping
instruction does not have to be a memory instruction.
It could be a ptrtoint instruction like in the added test
@earliest_escape_ptrtoint, which subsequently gets removed. We need to
invalidate the EarliestEscape entry referring to the ptrtoint when
deleting it.
This fixes the crash mentioned in
https://bugs.chromium.org/p/chromium/issues/detail?id=1252762#c6
This reverts commit bb9333c350.
This exposes another existing bug that causes an infinite loop as shown in
D110170
...so reverting while I look at another fix.
It caused compiler crashes, see comment on the code review for repro.
> This is basically D108837 but for jump threading. Free instructions
> should be ignored for the threading decision. JumpThreading already
> skips some free instructions (like pointer bitcasts), but does not
> skip various free intrinsics -- in fact, it currently gives them a
> fairly large cost of 2.
>
> Differential Revision: https://reviews.llvm.org/D110290
This reverts commit 1e3c6fc7cb.
When moving an entire basic block BB before InsertPoint, currently
we check for all instructions whether the operands dominates
InsertPoint, however, this can be improved such that even an
operand does not dominate InsertPoint, as long as it appears as
a previous instruction in the same BB, it is safe to move.
Reviewed By: Whitney
Differential Revision: https://reviews.llvm.org/D110378
There are several places in the code that are currently broken as
they assume an Instruction always has a parent Function when
attempting to get the vscale_range attribute. This patch adds checks
that an Instruction has a parent.
I've added a test for a parentless @llvm.vscale intrinsic call here:
unittests/Analysis/ValueTrackingTest.cpp
Differential Revision: https://reviews.llvm.org/D110158
This is basically D108837 but for jump threading. Free instructions
should be ignored for the threading decision. JumpThreading already
skips some free instructions (like pointer bitcasts), but does not
skip various free intrinsics -- in fact, it currently gives them a
fairly large cost of 2.
Differential Revision: https://reviews.llvm.org/D110290
While both GlobalAlias and GlobalIFunc are GlobalIndirectSymbol, their
`getIndirectSymbol()` usage is quite different (GlobalIFunc's resolver
is an entity different from GlobalIFunc itself).
As discussed on https://lists.llvm.org/pipermail/llvm-dev/2020-September/144904.html
("[IR] Modelling of GlobalIFunc"), the name `getBaseObject` is confusing when
used with GlobalIFunc.
To resolve the confusion:
* Move GloalIndirectSymol::getBaseObject to GlobalAlias:: (GlobalIFunc should use `getResolver` instead)
* Change GlobalValue::getBaseObject not to inspect GlobalIFunc. Note: the function has 7 references.
* Add GlobalIFunc::getResolverFunction to peel off potential ConstantExpr indirection
(`strlen` in `test/LTO/Resolution/X86/ifunc.ll`)
Note: GlobalIFunc::getResolver (like GlobalAlias::getAliasee which does not peel
off ConstantExpr indirection) is kept to be used by ValueEnumerator.
Reviewed By: ibookstein
Differential Revision: https://reviews.llvm.org/D109792
At the moment, DSE only considers whether a pointer may be captured at
all in a function. This leads to cases where we fail to remove stores to
local objects because we do not check if they escape before potential
read-clobbers or after.
Doing context-sensitive escape queries in isReadClobber has been removed
a while ago in d1a1cce5b1 to save compile-time. See PR50220 for more
context.
This patch introduces a new capture tracker, which keeps track of the
'earliest' capture. An instruction A is considered earlier than instruction
B, if A dominates B. If 2 escapes do not dominate each other, the
terminator of the common dominator is chosen. If not all uses cannot be
analyzed, the earliest escape is set to the first instruction in the
function entry block.
If the query instruction dominates the earliest escape and is not in a
cycle, then pointer does not escape before the query instruction.
This patch uses this information when checking if a load of a loaded
underlying object may alias a write to a stack object. If the stack
object does not escape before the load, they do not alias.
I will share a follow-up patch to also use the information for call
instructions to fix PR50220.
In terms of compile-time, the impact is low in general,
NewPM-O3: +0.05%
NewPM-ReleaseThinLTO: +0.05%
NewPM-ReleaseLTO-g: +0.03
with the largest change being tramp3d-v4 (+0.30%)
http://llvm-compile-time-tracker.com/compare.php?from=1a3b3301d7aa9ab25a8bdf045c77298b087e3930&to=bc6c6899cae757c3480f4ad4874a76fc1eafb0be&stat=instructions
Compared to always computing the capture information on demand, we get
the following benefits from the caching:
NewPM-O3: -0.03%
NewPM-ReleaseThinLTO: -0.08%
NewPM-ReleaseLTO-g: -0.04%
The biggest speedup is tramp3d-v4 (-0.21%).
http://llvm-compile-time-tracker.com/compare.php?from=0b0c99177d1511469c633282ef67f20c851f58b1&to=bc6c6899cae757c3480f4ad4874a76fc1eafb0be&stat=instructions
Overall there is a small, but noticeable benefit from caching. I am not
entirely sure if the speedups warrant the extra complexity of caching.
The way the caching works also means that we might miss a few cases, as
it is less precise. Also, there may be a better way to cache things.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D109844
The NFC commit e5692a564a changed the logic for
DomTreeUpdates to use the range [succ_begin, succ_begin) when
looking for SuccsOfPredBB rather than using [succ_begin, succ_end).
As the commit was NFC this is identified as a typo (it has been
discussed briefly in phabricator).
The typo was found when inspecting the code, so I've got no idea if
changing back to the old range has any significant impact (such as
solving any PR:s or causing some new problems). But at least this
restores the code to the originally indented behavior.
Bisecting and reducing opt pipelines that includes the
ModuleInlinerWrapperPass has turned out to be a bit problematic.
This is far from perfect (it still lacks information about inline
advisor params etc.), but it should give some kind of hint to what
the wrapped pipeline looks like when using -print-pipeline-passes.
Reviewed By: aeubanks, mtrofin
Differential Revision: https://reviews.llvm.org/D109878
This patch fixes a problem when the AAKernelInfo state was invalidated,
e.g., due to `optnone` for a kernel, but not all parts indicated the
invalidation properly. We further eliminate most full state
invalidations as they should never be necessary.
Differential Revision: https://reviews.llvm.org/D109468
This is a follow-up of D110029, which uses bitset to indicate execution mode. This patches makes the changes in the function call.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D110279
When determining whether to fold branches to a common destination by
merging two blocks, SimplifyCFG will count the number of instructions to
be moved into the first basic block. However, there's no reason to count
free instructions like bitcasts and other similar instructions.
This resolves missed branch foldings with -fstrict-vtable-pointers in
llvm-test-suite's lambda benchmark.
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D108837
Avoid relying on the default cost kinds in TTI calls (we already do this in other places in SLP) - noticed while trying to see how much work it'd be to extend D110242 and remove all remaining uses of default CostKind arguments.
This patch is for fixing potential shufflevector-related bugs like D93818.
As D93818, this patch change shufflevector's default placeholder to poison.
To reduce risk, it was divided into several patches, and this patch is for InstCombineVectorOps.
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D110230
The execution mode of a kernel is stored in a global variable, whose value means:
- 0 - SPMD mode
- 1 - indicates generic mode
- 2 - SPMD mode execution with generic mode semantics
We are going to add support for SIMD execution mode. It will be come with another
execution mode, such as SIMD-generic mode. As a result, this value-based indicator
is not flexible.
This patch changes to bitset based solution to encode execution mode. Each
position is:
[0] - generic mode
[1] - SPMD mode
[2] - SIMD mode (will be added later)
In this way, `0x1` is generic mode, `0x2` is SPMD mode, and `0x3` is SPMD mode
execution with generic mode semantics. In the future after we add the support for
SIMD mode, `0b1xx` will be in SIMD mode.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D110029
This patch is for fixing potential shufflevector-related bugs like D93818.
As D93818, this patch change shufflevector's default placeholder to poison.
To reduce risk, it was divided into several patches, and this patch is for InstCombineCompares and InstructionCombining.
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D110227
This patch is for fixing potential shufflevector-related bugs like D93818.
As D93818, this patch change shufflevector's default placeholder to poison.
To reduce risk, it was divided into several patches, and this patch is for InstCombineCasts.
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D110226
Summary:
The thread ID function was reintroduced in D110195, but could
potentially be removed by the optimizer. Make the function noinline to
preserve the call sites and add it to the externalization RAII so its
definition is not removed by the attributor.
IR with matrix intrinsics is likely to also contain large vector
operations, which can benefit from early simplifications.
This is the last step in a series of changes to improve code-gen for
code using matrix subscript operators with the C/C++ matrix extension in
CLang, like
using matrix_t = double __attribute__((matrix_type(15, 15)));
void foo(unsigned i, matrix_t &A, matrix_t &B) {
for (unsigned j = 0; j < 4; ++j)
for (unsigned k = 0; k < i; k++)
B[k][j] -= A[k][j] * B[i][j];
}
https://clang.godbolt.org/z/6dKxK1Ed7
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D102496
This reverts commit 2f6b07316f.
This caused several bots to hit an infinite loop at stage 2,
so it needs to be reverted while figuring out how to fix that.
The folding rule (select C, (gep Ptr, Idx), Ptr) -> (gep Ptr, (select C,
Idx, 0)) creates a malformed SELECT IR if C is a vector while Idx is scalar.
SELECT VecC, ScalarIdx, 0
We could splat Idx to a vector but it defeats the purpose of
optimisation. Don't apply the folding rule in this case.
This fixes a regression from commit d561b6fbdb.
Congzhe Cao