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Make InstCombineStoreToCast handle aggregates more aggressively, 

handling the case in Transforms/InstCombine/cast-store-gep.ll, which
is a heavily reduced testcase from Clang on x86-64.

llvm-svn: 62904
This commit is contained in:
Chris Lattner 2009-01-24 01:00:13 +00:00
parent f08ac278ed
commit 72cd68fe64
2 changed files with 65 additions and 18 deletions
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66
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -7700,12 +7700,12 @@ Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
/// FindElementAtOffset - Given a type and a constant offset, determine whether
/// or not there is a sequence of GEP indices into the type that will land us at
/// the specified offset. If so, fill them into NewIndices and return true,
/// otherwise return false.
static bool FindElementAtOffset(const Type *Ty, int64_t Offset,
SmallVectorImpl<Value*> &NewIndices,
const TargetData *TD) {
if (!Ty->isSized()) return false;
/// the specified offset. If so, fill them into NewIndices and return the
/// resultant element type, otherwise return null.
static const Type *FindElementAtOffset(const Type *Ty, int64_t Offset,
SmallVectorImpl<Value*> &NewIndices,
const TargetData *TD) {
if (!Ty->isSized()) return 0;
// Start with the index over the outer type. Note that the type size
// might be zero (even if the offset isn't zero) if the indexed type
@ -7731,7 +7731,7 @@ static bool FindElementAtOffset(const Type *Ty, int64_t Offset,
while (Offset) {
// Indexing into tail padding between struct/array elements.
if (uint64_t(Offset*8) >= TD->getTypeSizeInBits(Ty))
return false;
return 0;
if (const StructType *STy = dyn_cast<StructType>(Ty)) {
const StructLayout *SL = TD->getStructLayout(STy);
@ -7751,11 +7751,11 @@ static bool FindElementAtOffset(const Type *Ty, int64_t Offset,
Ty = AT->getElementType();
} else {
// Otherwise, we can't index into the middle of this atomic type, bail.
return false;
return 0;
}
}
return true;
return Ty;
}
/// @brief Implement the transforms for cast of pointer (bitcast/ptrtoint)
@ -11139,7 +11139,8 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
}
/// InstCombineStoreToCast - Fold store V, (cast P) -> store (cast V), P
/// when possible.
/// when possible. This makes it generally easy to do alias analysis and/or
/// SROA/mem2reg of the memory object.
static Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) {
User *CI = cast<User>(SI.getOperand(1));
Value *CastOp = CI->getOperand(0);
@ -11153,18 +11154,34 @@ static Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) {
if (!DestPTy->isInteger() && !isa<PointerType>(DestPTy))
return 0;
/// NewGEPIndices - If SrcPTy is an aggregate type, we can emit a "noop gep"
/// to its first element. This allows us to handle things like:
/// store i32 xxx, (bitcast {foo*, float}* %P to i32*)
/// on 32-bit hosts.
SmallVector<Value*, 4> NewGEPIndices;
// If the source is an array, the code below will not succeed. Check to
// see if a trivial 'gep P, 0, 0' will help matters. Only do this for
// constants.
if (const ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy))
if (Constant *CSrc = dyn_cast<Constant>(CastOp))
if (ASrcTy->getNumElements() != 0) {
Value* Idxs[2];
Idxs[0] = Idxs[1] = Constant::getNullValue(Type::Int32Ty);
CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs, 2);
SrcTy = cast<PointerType>(CastOp->getType());
SrcPTy = SrcTy->getElementType();
if (isa<ArrayType>(SrcPTy) || isa<StructType>(SrcPTy)) {
// Index through pointer.
Constant *Zero = Constant::getNullValue(Type::Int32Ty);
NewGEPIndices.push_back(Zero);
while (1) {
if (const StructType *STy = dyn_cast<StructType>(SrcPTy)) {
NewGEPIndices.push_back(Zero);
SrcPTy = STy->getElementType(0);
} else if (const ArrayType *ATy = dyn_cast<ArrayType>(SrcPTy)) {
NewGEPIndices.push_back(Zero);
SrcPTy = ATy->getElementType();
} else {
break;
}
}
SrcTy = PointerType::get(SrcPTy, SrcTy->getAddressSpace());
}
if (!SrcPTy->isInteger() && !isa<PointerType>(SrcPTy))
return 0;
@ -11192,6 +11209,19 @@ static Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) {
if (isa<PointerType>(SIOp0->getType()))
opcode = Instruction::PtrToInt;
}
// SIOp0 is a pointer to aggregate and this is a store to the first field,
// emit a GEP to index into its first field.
if (!NewGEPIndices.empty()) {
if (Constant *C = dyn_cast<Constant>(CastOp))
CastOp = ConstantExpr::getGetElementPtr(C, &NewGEPIndices[0],
NewGEPIndices.size());
else
CastOp = IC.InsertNewInstBefore(
GetElementPtrInst::Create(CastOp, NewGEPIndices.begin(),
NewGEPIndices.end()), SI);
}
if (Constant *C = dyn_cast<Constant>(SIOp0))
NewCast = ConstantExpr::getCast(opcode, C, CastDstTy);
else

17
llvm/test/Transforms/InstCombine/cast-store-gep.ll Normal file
View File

@ -0,0 +1,17 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep inttoptr
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep alloca
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-apple-darwin10.0"
%T = type { i8*, i8 }
define i8* @test(i8* %Val, i64 %V) nounwind {
entry:
%A = alloca %T, align 8
%mrv_gep = bitcast %T* %A to i64* ; <i64*> [#uses=1]
%B = getelementptr %T* %A, i64 0, i32 0 ; <i8**> [#uses=1]
store i64 %V, i64* %mrv_gep
%C = load i8** %B, align 8 ; <i8*> [#uses=1]
ret i8* %C
}