diff options
Diffstat (limited to 'lib/Transforms')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineCalls.cpp | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp index 4929f4070f..1371fa7f1a 100644 --- a/lib/Transforms/InstCombine/InstCombineCalls.cpp +++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp @@ -308,9 +308,14 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) { Value *Op1 = II->getOperand(1); bool Min = (cast<ConstantInt>(II->getOperand(2))->getZExtValue() == 1); + // We need target data for just about everything so depend on it. if (!TD) break; + + // Get to the real allocated thing and offset as fast as possible. Op1 = Op1->stripPointerCasts(); + // If we've stripped down to a single global variable that we + // can know the size of then just return that. if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op1)) { if (GV->hasDefinitiveInitializer()) { Constant *C = GV->getInitializer(); @@ -320,7 +325,27 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) { Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL); return ReplaceInstUsesWith(CI, RetVal); } - } + } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op1)) { + + // Only handle constant GEPs here. + if (CE->getOpcode() != Instruction::GetElementPtr) break; + GEPOperator *GEP = cast<GEPOperator>(CE); + + // Get what we're pointing to and its size. + const PointerType *PT = + cast<PointerType>(GEP->getPointerOperand()->getType()); + size_t Size = TD->getTypeAllocSize(PT->getElementType()); + + // Get the current byte offset into the thing. + SmallVector<Value*, 8> Ops(CE->op_begin()+1, CE->op_end()); + size_t Offset = TD->getIndexedOffset(PT, &Ops[0], Ops.size()); + + assert(Size >= Offset); + + Constant *RetVal = ConstantInt::get(ReturnTy, Size-Offset); + return ReplaceInstUsesWith(CI, RetVal); + + } } case Intrinsic::bswap: // bswap(bswap(x)) -> x |