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[FunctionAttrs] Handle ConstantRange overflow in memset initializes inference (#145739)

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Avoid constructing invalid ConstantRange when Offset + Length in memset
overflows signed 64-bit integer space. This prevents assertion failures
when inferring the initializes attribute.

Fixes #140345
This commit is contained in:
Shivam Gupta 2025-07-01 18:34:52 +05:30 committed by GitHub
parent 3702d64801
commit e44fbea0a1
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GPG Key ID: B5690EEEBB952194
2 changed files with 29 additions and 5 deletions
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20
llvm/lib/Transforms/IPO/FunctionAttrs.cpp
View File

@ -675,14 +675,24 @@ ArgumentAccessInfo getArgumentAccessInfo(const Instruction *I,
[](Value *Length,
std::optional<int64_t> Offset) -> std::optional<ConstantRange> {
auto *ConstantLength = dyn_cast<ConstantInt>(Length);
if (ConstantLength && Offset &&
ConstantLength->getValue().isStrictlyPositive()) {
return ConstantRange(
APInt(64, *Offset, true),
APInt(64, *Offset + ConstantLength->getSExtValue(), true));
if (ConstantLength && Offset) {
int64_t Len = ConstantLength->getSExtValue();
// Reject zero or negative lengths
if (Len <= 0)
return std::nullopt;
APInt Low(64, *Offset, true);
bool Overflow;
APInt High = Low.sadd_ov(APInt(64, Len, true), Overflow);
if (Overflow)
return std::nullopt;
return ConstantRange(Low, High);
}
return std::nullopt;
};
if (auto *SI = dyn_cast<StoreInst>(I)) {
if (SI->isSimple() && &SI->getOperandUse(1) == ArgUse.U) {
// Get the fixed type size of "SI". Since the access range of a write

14
llvm/test/Transforms/FunctionAttrs/initializes.ll
View File

@ -649,3 +649,17 @@ define void @range_overflows_signed_64_bit_int(ptr %arg) {
store i32 0, ptr %getelementptr
ret void
}
; We should bail if the memset range overflows a signed 64-bit int.
define void @memset_large_offset_nonzero_size(ptr %dst) {
; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(argmem: write)
; CHECK-LABEL: define void @memset_large_offset_nonzero_size(
; CHECK-SAME: ptr writeonly captures(none) [[DST:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[OFFSET:%.*]] = getelementptr inbounds i8, ptr [[DST]], i64 9223372036854775805
; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr [[OFFSET]], i8 0, i64 3, i1 false)
; CHECK-NEXT: ret void
;
%offset = getelementptr inbounds i8, ptr %dst, i64 9223372036854775805
call void @llvm.memset.p0.i64(ptr %offset, i8 0, i64 3, i1 false)
ret void
}