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[ArgPromotion] Remove incorrect TranspBlocks set for loads. (#84835)

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The TranspBlocks set was used to cache aliasing decision for all
processed loads in the parent loop. This is incorrect, because each load
can access a different location, which means one load not being modified
in a block doesn't translate to another load not being modified in the
same block.

All loads access the same underlying object, so we could perhaps use a
location without size for all loads and retain the cache, but that would
mean we loose precision.

For now, just drop the cache.

Fixes https://github.com/llvm/llvm-project/issues/84807

PR: https://github.com/llvm/llvm-project/pull/84835
This commit is contained in:
Florian Hahn 2024-03-12 09:47:42 +00:00 committed by GitHub
parent a3b52509d5
commit bba4a1daff
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GPG Key ID: B5690EEEBB952194
2 changed files with 8 additions and 12 deletions
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6
llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
View File

@ -653,10 +653,6 @@ static bool findArgParts(Argument *Arg, const DataLayout &DL, AAResults &AAR,
// check to see if the pointer is guaranteed to not be modified from entry of
// the function to each of the load instructions.
// Because there could be several/many load instructions, remember which
// blocks we know to be transparent to the load.
df_iterator_default_set<BasicBlock *, 16> TranspBlocks;
for (LoadInst *Load : Loads) {
// Check to see if the load is invalidated from the start of the block to
// the load itself.
@ -670,7 +666,7 @@ static bool findArgParts(Argument *Arg, const DataLayout &DL, AAResults &AAR,
// To do this, we perform a depth first search on the inverse CFG from the
// loading block.
for (BasicBlock *P : predecessors(BB)) {
for (BasicBlock *TranspBB : inverse_depth_first_ext(P, TranspBlocks))
for (BasicBlock *TranspBB : inverse_depth_first(P))
if (AAR.canBasicBlockModify(*TranspBB, Loc))
return false;
}

14
llvm/test/Transforms/ArgumentPromotion/aliasing-and-non-aliasing-loads-with-clobber.ll
View File

@ -7,17 +7,14 @@ target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:
; Test case for https://github.com/llvm/llvm-project/issues/84807.
; FIXME: Currently the loads from @callee are moved to @caller, even though
; the store in %then may aliases to load from %q.
; Make sure the loads from @callee are not moved to @caller, as the store
; in %then may aliases to load from %q.
define i32 @caller1(i1 %c) {
; CHECK-LABEL: define i32 @caller1(
; CHECK-SAME: i1 [[C:%.*]]) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[F_VAL:%.*]] = load i16, ptr @f, align 8
; CHECK-NEXT: [[TMP0:%.*]] = getelementptr i8, ptr @f, i64 8
; CHECK-NEXT: [[F_VAL1:%.*]] = load i64, ptr [[TMP0]], align 8
; CHECK-NEXT: call void @callee1(i16 [[F_VAL]], i64 [[F_VAL1]], i1 [[C]])
; CHECK-NEXT: call void @callee1(ptr noundef nonnull @f, i1 [[C]])
; CHECK-NEXT: ret i32 0
;
entry:
@ -27,13 +24,16 @@ entry:
define internal void @callee1(ptr nocapture noundef readonly %q, i1 %c) {
; CHECK-LABEL: define internal void @callee1(
; CHECK-SAME: i16 [[Q_0_VAL:%.*]], i64 [[Q_8_VAL:%.*]], i1 [[C:%.*]]) {
; CHECK-SAME: ptr nocapture noundef readonly [[Q:%.*]], i1 [[C:%.*]]) {
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[C]], label [[THEN:%.*]], label [[EXIT:%.*]]
; CHECK: then:
; CHECK-NEXT: store i16 123, ptr @f, align 8
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[Q_0_VAL:%.*]] = load i16, ptr [[Q]], align 8
; CHECK-NEXT: [[GEP_8:%.*]] = getelementptr inbounds i8, ptr [[Q]], i64 8
; CHECK-NEXT: [[Q_8_VAL:%.*]] = load i64, ptr [[GEP_8]], align 8
; CHECK-NEXT: call void @use(i16 [[Q_0_VAL]], i64 [[Q_8_VAL]])
; CHECK-NEXT: ret void
;