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[Scalarizer] Fix out-of-bounds crash (#180359)

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When processing an extractelement instruction with an index that exceeds
the vector size (e.g., extracting index 2147483647 from a 4-element
vector), the scalarizer would calculate an out-of-bounds Fragment index
and crash with an assertion failure in `SmallVector::operator[]`.

This PR adds a bounds check in
`ScalarizerVisitor::visitExtractElementInst` to prevent a crash when the
extractelement index is out of bounds.

Fixes #179880
This commit is contained in:
bala-bhargav 2026-02-21 23:25:30 +05:30 committed by GitHub
parent a67bf7d796
commit 6e0054aa51
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2 changed files with 12 additions and 0 deletions
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2
llvm/lib/Transforms/Scalar/Scalarizer.cpp
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@ -1133,6 +1133,8 @@ bool ScalarizerVisitor::visitExtractElementInst(ExtractElementInst &EEI) {
if (auto *CI = dyn_cast<ConstantInt>(ExtIdx)) {
unsigned Idx = CI->getZExtValue();
if (Idx >= VS->VecTy->getNumElements())
return false;
unsigned Fragment = Idx / VS->NumPacked;
Value *Res = Op0[Fragment];
bool IsPacked = VS->NumPacked > 1;

10
llvm/test/Transforms/Scalarizer/constant-extractelement.ll
View File

@ -16,3 +16,13 @@ define i32 @f1(ptr %src, i32 %index) {
%val2 = extractelement <4 x i32> %val1, i32 3
ret i32 %val2
}
; Test that out-of-bounds extractelement doesn't crash the scalarizer.
define ptr @oob_extract() {
; ALL-LABEL: @oob_extract(
; ALL-NEXT: [[E:%.*]] = extractelement <4 x ptr> zeroinitializer, i32 100
; ALL-NEXT: ret ptr [[E]]
;
%E = extractelement <4 x ptr> zeroinitializer, i32 100
ret ptr %E
}