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authorNikita Popov <npopov@redhat.com>2025-03-11 09:02:34 +0100
committerGitHub <noreply@github.com>2025-03-11 09:02:34 +0100
commit8758e5fe47b5cf2d39d94ee6dc8834755c7687d9 (patch)
tree5814112b977e6f4bf73a188d50e9524c02bc965d /llvm/lib/Analysis/ConstantFolding.cpp
parent4a4444c0b2f68bec1db8e2cc8d133982d5a339e3 (diff)
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[ConstantFolding] Fix handling of index width != pointer width (#130608)
Per LangRef: > The offsets are then added to the low bits of the base address up to the index type width, with silently-wrapping two’s complement arithmetic. If the pointer size is larger than the index size, this means that the bits outside the index type width will not be affected. The transform as implemented was doubly wrong, because it just truncated the original base pointer to the index width, losing the top bits entirely. Make sure we preserve the bits and use wrapping arithmetic within the low bits.
Diffstat (limited to 'llvm/lib/Analysis/ConstantFolding.cpp')
-rw-r--r--llvm/lib/Analysis/ConstantFolding.cpp9
1 files changed, 6 insertions, 3 deletions
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index d645bf8..b0ba25c 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -943,18 +943,21 @@ Constant *SymbolicallyEvaluateGEP(const GEPOperator *GEP,
// If the base value for this address is a literal integer value, fold the
// getelementptr to the resulting integer value casted to the pointer type.
- APInt BasePtr(BitWidth, 0);
+ APInt BasePtr(DL.getPointerTypeSizeInBits(Ptr->getType()), 0);
if (auto *CE = dyn_cast<ConstantExpr>(Ptr)) {
if (CE->getOpcode() == Instruction::IntToPtr) {
if (auto *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
- BasePtr = Base->getValue().zextOrTrunc(BitWidth);
+ BasePtr = Base->getValue().zextOrTrunc(BasePtr.getBitWidth());
}
}
auto *PTy = cast<PointerType>(Ptr->getType());
if ((Ptr->isNullValue() || BasePtr != 0) &&
!DL.isNonIntegralPointerType(PTy)) {
- Constant *C = ConstantInt::get(Ptr->getContext(), Offset + BasePtr);
+ // If the index size is smaller than the pointer size, add to the low
+ // bits only.
+ BasePtr.insertBits(BasePtr.trunc(BitWidth) + Offset, 0);
+ Constant *C = ConstantInt::get(Ptr->getContext(), BasePtr);
return ConstantExpr::getIntToPtr(C, ResTy);
}