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[DA] Check element size when analyzing deps between same instruction #148813

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Merged
merged 1 commit into from
Jul 17, 2025
Merged

[DA] Check element size when analyzing deps between same instruction #148813

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14 changes: 6 additions & 8 deletions llvm/lib/Analysis/DependenceAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3670,14 +3670,12 @@ DependenceInfo::depends(Instruction *Src, Instruction *Dst,
const SCEV *SrcEv = SE->getMinusSCEV(SrcSCEV, SrcBase);
const SCEV *DstEv = SE->getMinusSCEV(DstSCEV, DstBase);

if (Src != Dst) {
// Check that memory access offsets are multiples of element sizes.
if (!SE->isKnownMultipleOf(SrcEv, EltSize, Assume) ||
!SE->isKnownMultipleOf(DstEv, EltSize, Assume)) {
LLVM_DEBUG(dbgs() << "can't analyze SCEV with different offsets\n");
return std::make_unique<Dependence>(Src, Dst,
SCEVUnionPredicate(Assume, *SE));
}
// Check that memory access offsets are multiples of element sizes.
if (!SE->isKnownMultipleOf(SrcEv, EltSize, Assume) ||
!SE->isKnownMultipleOf(DstEv, EltSize, Assume)) {
LLVM_DEBUG(dbgs() << "can't analyze SCEV with different offsets\n");
return std::make_unique<Dependence>(Src, Dst,
SCEVUnionPredicate(Assume, *SE));
}

if (!Assume.empty()) {
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6 changes: 3 additions & 3 deletions llvm/test/Analysis/DependenceAnalysis/DifferentOffsets.ll
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Expand Up @@ -11,7 +11,7 @@
define i32 @alias_with_different_offsets(ptr nocapture %A) {
; CHECK-LABEL: 'alias_with_different_offsets'
; CHECK-NEXT: Src: store i32 2, ptr %arrayidx, align 1 --> Dst: store i32 2, ptr %arrayidx, align 1
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: store i32 2, ptr %arrayidx, align 1 --> Dst: %0 = load i32, ptr %A, align 1
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %0 = load i32, ptr %A, align 1 --> Dst: %0 = load i32, ptr %A, align 1
Expand Down Expand Up @@ -207,11 +207,11 @@ end:
; *((long long *)idx) = 1;
; }
;
; FIXME: There are loop-carried dependencies across iterations in the store.
; There are loop-carried dependencies across iterations in the store.
define void @multidim_accesses2(ptr %A) {
; CHECK-LABEL: 'multidim_accesses2'
; CHECK-NEXT: Src: store i64 1, ptr %idx, align 4 --> Dst: store i64 1, ptr %idx, align 4
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: da analyze - confused!
;
entry:
br label %for.i
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3 changes: 3 additions & 0 deletions llvm/test/Analysis/DependenceAnalysis/MIVCheckConst.ll
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Expand Up @@ -40,6 +40,9 @@ define void @test(ptr %A, ptr %B, i1 %arg, i32 %n, i32 %m) #0 align 2 {
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %v27 = load <32 x i32>, ptr %v25, align 256 --> Dst: %v27 = load <32 x i32>, ptr %v25, align 256
; CHECK-NEXT: da analyze - consistent input [0 S S]!
; CHECK-NEXT: Runtime Assumptions:
; CHECK-NEXT: Equal predicate: (zext i7 (4 * (trunc i32 %v1 to i7) * (1 + (trunc i32 %n to i7))) to i32) == 0
; CHECK-NEXT: Equal predicate: (8 * (zext i4 (trunc i32 %v1 to i4) to i32))<nuw><nsw> == 0
; CHECK-NEXT: Src: %v27 = load <32 x i32>, ptr %v25, align 256 --> Dst: %v32 = load <32 x i32>, ptr %v30, align 128
; CHECK-NEXT: da analyze - input [* S S|<]!
; CHECK-NEXT: Runtime Assumptions:
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