From 9fb921308375b519b742484fbed7407cbe62bfd6 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Wed, 12 Apr 2006 18:09:35 +0000 Subject: [PATCH] Turn casts into getelementptr's when possible. This enables SROA to be more aggressive in some cases where LLVMGCC 4 is inserting casts for no reason. This implements InstCombine/cast.ll:test27/28. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27620 91177308-0d34-0410-b5e6-96231b3b80d8 --- .../Scalar/InstructionCombining.cpp | 23 +++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index f79a48e3bda..f9b01c7a30d 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -4813,7 +4813,30 @@ Instruction *InstCombiner::visitCastInst(CastInst &CI) { if (isa(Src)) if (Instruction *NV = FoldOpIntoPhi(CI)) return NV; + + // If the source and destination are pointers, and this cast is equivalent to + // a getelementptr X, 0, 0, 0... turn it into the appropriate getelementptr. + // This can enhance SROA and other transforms that want type-safe pointers. + if (const PointerType *DstPTy = dyn_cast(CI.getType())) + if (const PointerType *SrcPTy = dyn_cast(Src->getType())) { + const Type *DstTy = DstPTy->getElementType(); + const Type *SrcTy = SrcPTy->getElementType(); + + Constant *ZeroUInt = Constant::getNullValue(Type::UIntTy); + unsigned NumZeros = 0; + while (SrcTy != DstTy && + isa(SrcTy) && !isa(SrcTy)) { + SrcTy = cast(SrcTy)->getTypeAtIndex(ZeroUInt); + ++NumZeros; + } + // If we found a path from the src to dest, create the getelementptr now. + if (SrcTy == DstTy) { + std::vector Idxs(NumZeros+1, ZeroUInt); + return new GetElementPtrInst(Src, Idxs); + } + } + // If the source value is an instruction with only this use, we can attempt to // propagate the cast into the instruction. Also, only handle integral types // for now.