From 8758e5fe47b5cf2d39d94ee6dc8834755c7687d9 Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Tue, 11 Mar 2025 09:02:34 +0100 Subject: [ConstantFolding] Fix handling of index width != pointer width (#130608) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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. --- llvm/lib/Analysis/ConstantFolding.cpp | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'llvm/lib/Analysis/ConstantFolding.cpp') 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(Ptr)) { if (CE->getOpcode() == Instruction::IntToPtr) { if (auto *Base = dyn_cast(CE->getOperand(0))) - BasePtr = Base->getValue().zextOrTrunc(BitWidth); + BasePtr = Base->getValue().zextOrTrunc(BasePtr.getBitWidth()); } } auto *PTy = cast(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); } -- cgit v1.1