diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Analysis/ConstantFolding.cpp | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp index ded1d0767c..6c5b75502f 100644 --- a/lib/Analysis/ConstantFolding.cpp +++ b/lib/Analysis/ConstantFolding.cpp @@ -575,8 +575,26 @@ static Constant *SymbolicallyEvaluateGEP(Constant *const *Ops, unsigned NumOps, // If this is a constant expr gep that is effectively computing an // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12' for (unsigned i = 1; i != NumOps; ++i) - if (!isa<ConstantInt>(Ops[i])) + if (!isa<ConstantInt>(Ops[i])) { + + // If this is "gep i8* Ptr, (sub 0, V)", fold this as: + // "inttoptr (sub (ptrtoint Ptr), V)" + if (NumOps == 2 && + cast<PointerType>(ResultTy)->getElementType()->isIntegerTy(8)) { + ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[1]); + if (CE && CE->getOpcode() == Instruction::Sub && + isa<ConstantInt>(CE->getOperand(0)) && + cast<ConstantInt>(CE->getOperand(0))->isZero()) { + Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType()); + Res = ConstantExpr::getSub(Res, CE->getOperand(1)); + Res = ConstantExpr::getIntToPtr(Res, ResultTy); + if (ConstantExpr *ResCE = dyn_cast<ConstantExpr>(Res)) + Res = ConstantFoldConstantExpression(ResCE, TD); + return Res; + } + } return 0; + } APInt Offset = APInt(BitWidth, TD->getIndexedOffset(Ptr->getType(), |