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[SCEV] Don't create SCEVPtrToAddr for unstable pointer representations. #180718

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Merged
fhahn merged 2 commits into from
Feb 10, 2026
Merged

[SCEV] Don't create SCEVPtrToAddr for unstable pointer representations. #180718

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e26e3e5
[SCEV] Don't create SCEVPtrToAddr for unstable pointer representations.
fhahn Feb 10, 2026
f822e20
Merge branch 'main' into scev-ptrtoaddr-unstable
fhahn Feb 10, 2026
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14 changes: 12 additions & 2 deletions llvm/lib/Analysis/ScalarEvolution.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1127,6 +1127,12 @@ const SCEV *ScalarEvolution::getLosslessPtrToIntExpr(const SCEV *Op) {

const SCEV *ScalarEvolution::getPtrToAddrExpr(const SCEV *Op) {
assert(Op->getType()->isPointerTy() && "Op must be a pointer");

// Treat pointers with unstable representation conservatively, since the
// address bits may change.
if (DL.hasUnstableRepresentation(Op->getType()))
return getCouldNotCompute();

Type *Ty = DL.getAddressType(Op->getType());

// Use the rewriter to sink the cast down to SCEVUnknown leaves.
Expand Down Expand Up @@ -8175,8 +8181,12 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
return getSCEV(U->getOperand(0));
break;

case Instruction::PtrToAddr:
return getPtrToAddrExpr(getSCEV(U->getOperand(0)));
case Instruction::PtrToAddr: {
const SCEV *IntOp = getPtrToAddrExpr(getSCEV(U->getOperand(0)));
if (isa<SCEVCouldNotCompute>(IntOp))
return getUnknown(V);
return IntOp;
}

case Instruction::PtrToInt: {
// Pointer to integer cast is straight-forward, so do model it.
Expand Down
9 changes: 3 additions & 6 deletions llvm/test/Analysis/ScalarEvolution/ptrtoaddr.ll
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Expand Up @@ -89,29 +89,27 @@ define void @ptrtoaddr_of_gep_with_unknown_int(ptr %in, ptr %out0, ptr %offset)
ret void
}

; FIXME: Currently not handled correctly.
; ptrtoaddr of a pointer with unstable representation should return SCEVUnknown.
define void @ptrtoaddr_unstable(ptr addrspace(2) %in, ptr %out) {
; CHECK-LABEL: 'ptrtoaddr_unstable'
; CHECK-NEXT: Classifying expressions for: @ptrtoaddr_unstable
; CHECK-NEXT: %p = ptrtoaddr ptr addrspace(2) %in to i64
; CHECK-NEXT: --> (ptrtoaddr ptr addrspace(2) %in to i64) U: full-set S: full-set
; CHECK-NEXT: --> %p U: full-set S: full-set
; CHECK-NEXT: Determining loop execution counts for: @ptrtoaddr_unstable
;
%p = ptrtoaddr ptr addrspace(2) %in to i64
store i64 %p, ptr %out
ret void
}

; FIXME: Currently not handled correctly.
; ptrtoaddr of GEP on unstable pointer should return SCEVUnknown.
define void @ptrtoaddr_unstable_gep(ptr addrspace(2) %in, ptr %out) {
; CHECK-LABEL: 'ptrtoaddr_unstable_gep'
; CHECK-NEXT: Classifying expressions for: @ptrtoaddr_unstable_gep
; CHECK-NEXT: %gep = getelementptr inbounds i8, ptr addrspace(2) %in, i64 42
; CHECK-NEXT: --> (42 + %in) U: full-set S: full-set
; CHECK-NEXT: %p = ptrtoaddr ptr addrspace(2) %gep to i64
; CHECK-NEXT: --> (42 + (ptrtoaddr ptr addrspace(2) %in to i64)) U: full-set S: full-set
; CHECK-NEXT: --> %p U: full-set S: full-set
; CHECK-NEXT: Determining loop execution counts for: @ptrtoaddr_unstable_gep
;
%gep = getelementptr inbounds i8, ptr addrspace(2) %in, i64 42
Expand All @@ -120,13 +118,12 @@ define void @ptrtoaddr_unstable_gep(ptr addrspace(2) %in, ptr %out) {
ret void
}

; FIXME: Currently not handled correctly.
; ptrtoaddr of nullptr in unstable address space should return SCEVUnknown.
define void @ptrtoaddr_unstable_null(ptr %out) {
; CHECK-LABEL: 'ptrtoaddr_unstable_null'
; CHECK-NEXT: Classifying expressions for: @ptrtoaddr_unstable_null
; CHECK-NEXT: %p = ptrtoaddr ptr addrspace(2) null to i64
; CHECK-NEXT: --> 0 U: [0,1) S: [0,1)
; CHECK-NEXT: --> %p U: [0,1) S: [0,1)
; CHECK-NEXT: Determining loop execution counts for: @ptrtoaddr_unstable_null
;
%p = ptrtoaddr ptr addrspace(2) null to i64
Expand Down
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