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LAA: strip unnecessary getUniqueCastUse #92119

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Jun 24, 2024
Merged

LAA: strip unnecessary getUniqueCastUse #92119

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34 changes: 6 additions & 28 deletions llvm/lib/Analysis/LoopAccessAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2873,21 +2873,6 @@ static Value *stripGetElementPtr(Value *Ptr, ScalarEvolution *SE, Loop *Lp) {
return GEP->getOperand(InductionOperand);
}

/// If a value has only one user that is a CastInst, return it.
static Value *getUniqueCastUse(Value *Ptr, Loop *Lp, Type *Ty) {
Value *UniqueCast = nullptr;
for (User *U : Ptr->users()) {
CastInst *CI = dyn_cast<CastInst>(U);
if (CI && CI->getType() == Ty) {
if (!UniqueCast)
UniqueCast = CI;
else
return nullptr;
}
}
return UniqueCast;
}

/// Get the stride of a pointer access in a loop. Looks for symbolic
/// strides "a[i*stride]". Returns the symbolic stride, or null otherwise.
static const SCEV *getStrideFromPointer(Value *Ptr, ScalarEvolution *SE, Loop *Lp) {
Expand Down Expand Up @@ -2950,21 +2935,14 @@ static const SCEV *getStrideFromPointer(Value *Ptr, ScalarEvolution *SE, Loop *L
return nullptr;

// Look for the loop invariant symbolic value.
const SCEVUnknown *U = dyn_cast<SCEVUnknown>(V);
if (!U) {
const auto *C = dyn_cast<SCEVIntegralCastExpr>(V);
if (!C)
return nullptr;
U = dyn_cast<SCEVUnknown>(C->getOperand());
if (!U)
return nullptr;
if (isa<SCEVUnknown>(V))
return V;

// Match legacy behavior - this is not needed for correctness
if (!getUniqueCastUse(U->getValue(), Lp, V->getType()))
return nullptr;
}
if (const auto *C = dyn_cast<SCEVIntegralCastExpr>(V))
if (isa<SCEVUnknown>(C->getOperand()))
return V;

return V;
return nullptr;
}

void LoopAccessInfo::collectStridedAccess(Value *MemAccess) {
Expand Down
15 changes: 11 additions & 4 deletions llvm/test/Analysis/LoopAccessAnalysis/symbolic-stride.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -170,16 +170,23 @@ define void @single_stride_castexpr_multiuse(i32 %offset, ptr %src, ptr %dst, i1
; CHECK-NEXT: %gep.src = getelementptr inbounds i32, ptr %src, i64 %iv.3
; CHECK-NEXT: Grouped accesses:
; CHECK-NEXT: Group [[GRP3]]:
; CHECK-NEXT: (Low: (((4 * %iv.1) + %dst) umin ((4 * %iv.1) + (4 * (sext i32 %offset to i64) * (200 + (-1 * (zext i32 %offset to i64))<nsw>)<nsw>) + %dst)) High: (4 + (((4 * %iv.1) + %dst) umax ((4 * %iv.1) + (4 * (sext i32 %offset to i64) * (200 + (-1 * (zext i32 %offset to i64))<nsw>)<nsw>) + %dst))))
; CHECK-NEXT: Member: {((4 * %iv.1) + %dst),+,(4 * (sext i32 %offset to i64))<nsw>}<%inner.loop>
; CHECK-NEXT: (Low: ((4 * %iv.1) + %dst) High: (804 + (4 * %iv.1) + (-4 * (zext i32 %offset to i64))<nsw> + %dst))
; CHECK-NEXT: Member: {((4 * %iv.1) + %dst),+,4}<%inner.loop>
; CHECK-NEXT: Group [[GRP4]]:
; CHECK-NEXT: (Low: ((4 * (zext i32 %offset to i64))<nuw><nsw> + %src) High: (804 + %src))
; CHECK-NEXT: Member: {((4 * (zext i32 %offset to i64))<nuw><nsw> + %src),+,4}<%inner.loop>
; CHECK-NEXT: (Low: (4 + %src) High: (808 + (-4 * (zext i32 %offset to i64))<nsw> + %src))
; CHECK-NEXT: Member: {(4 + %src),+,4}<%inner.loop>
; CHECK-EMPTY:
; CHECK-NEXT: Non vectorizable stores to invariant address were not found in loop.
; CHECK-NEXT: SCEV assumptions:
; CHECK-NEXT: Equal predicate: %offset == 1
; CHECK-EMPTY:
; CHECK-NEXT: Expressions re-written:
; CHECK-NEXT: [PSE] %gep.src = getelementptr inbounds i32, ptr %src, i64 %iv.3:
; CHECK-NEXT: {((4 * (zext i32 %offset to i64))<nuw><nsw> + %src),+,4}<%inner.loop>
; CHECK-NEXT: --> {(4 + %src),+,4}<%inner.loop>
; CHECK-NEXT: [PSE] %gep.dst = getelementptr i32, ptr %dst, i64 %iv.2:
; CHECK-NEXT: {((4 * %iv.1) + %dst),+,(4 * (sext i32 %offset to i64))<nsw>}<%inner.loop>
; CHECK-NEXT: --> {((4 * %iv.1) + %dst),+,4}<%inner.loop>
; CHECK-NEXT: outer.header:
; CHECK-NEXT: Report: loop is not the innermost loop
; CHECK-NEXT: Dependences:
Expand Down
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