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remove an extremely dubious instcombine transformation of

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extractelement(load).

llvm-svn: 81239
This commit is contained in:
Chris Lattner 2009-09-08 18:48:01 +00:00
parent 55eb4bffab
commit 5caba6ecdc
2 changed files with 13 additions and 64 deletions
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54
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -12130,48 +12130,20 @@ Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
}
if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0))) {
if (I->hasOneUse()) {
// Push extractelement into predecessor operation if legal and
// profitable to do so
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
bool isConstantElt = isa<ConstantInt>(EI.getOperand(1));
if (CheapToScalarize(BO, isConstantElt)) {
Value *newEI0 =
Builder->CreateExtractElement(BO->getOperand(0), EI.getOperand(1),
EI.getName()+".lhs");
Value *newEI1 =
Builder->CreateExtractElement(BO->getOperand(1), EI.getOperand(1),
EI.getName()+".rhs");
return BinaryOperator::Create(BO->getOpcode(), newEI0, newEI1);
}
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
// Instead of loading a vector, then doing an extract element out of it,
// just bitcast the pointer operand, do a gep, then load the result.
// This shrinks the vector load to a scalar load.
if (EI.getVectorOperandType()->getNumElements() != 1) {
unsigned AS = LI->getPointerAddressSpace();
Value *Ptr = Builder->CreateBitCast(I->getOperand(0),
PointerType::get(EI.getType(), AS),
I->getOperand(0)->getName());
Value *GEP =
Builder->CreateInBoundsGEP(Ptr, EI.getOperand(1),
I->getName()+".gep");
LoadInst *Load = Builder->CreateLoad(GEP, "tmp");
// Make sure the Load goes before the load instruction in the source,
// not wherever the extract happens to be.
if (Instruction *P = dyn_cast<Instruction>(Ptr))
P->moveBefore(I);
if (Instruction *G = dyn_cast<Instruction>(GEP))
G->moveBefore(I);
Load->moveBefore(I);
return ReplaceInstUsesWith(EI, Load);
}
// Push extractelement into predecessor operation if legal and
// profitable to do so
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
if (I->hasOneUse() &&
CheapToScalarize(BO, isa<ConstantInt>(EI.getOperand(1)))) {
Value *newEI0 =
Builder->CreateExtractElement(BO->getOperand(0), EI.getOperand(1),
EI.getName()+".lhs");
Value *newEI1 =
Builder->CreateExtractElement(BO->getOperand(1), EI.getOperand(1),
EI.getName()+".rhs");
return BinaryOperator::Create(BO->getOpcode(), newEI0, newEI1);
}
}
if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) {
} else if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) {
// Extracting the inserted element?
if (IE->getOperand(2) == EI.getOperand(1))
return ReplaceInstUsesWith(EI, IE->getOperand(1));

23
test/Transforms/InstCombine/vec_extract_elt2.ll
View File

@ -1,23 +0,0 @@
; RUN: opt %s -instcombine | llvm-dis | FileCheck %s
; The load replacing the extract element must occur before the call
; that may modify local array a.
declare void @mod_a_func(<4 x float>* %a);
; CHECK: load float* %arraydecay1, align 16
; CHECK: call void @mod_a_func
define void @cl_jpegenc_k2(<4 x float> addrspace(1)* %src, float addrspace(1)* %dst) {
%a = alloca [2 x <4 x float>], align 16
%arraydecay = getelementptr [2 x <4 x float>]* %a, i32 0, i32 0
%arrayidx31 = getelementptr <4 x float> addrspace(1)* %src, i32 0
%tmp32 = load <4 x float> addrspace(1)* %arrayidx31
store <4 x float> %tmp32, <4 x float>* %arraydecay, align 16
%tmp86 = load <4 x float>* %arraydecay, align 16
call void @mod_a_func(<4 x float>* %arraydecay)
%arrayidx132 = getelementptr float addrspace(1)* %dst, i32 0
%tmp236 = extractelement <4 x float> %tmp86, i32 0
store float %tmp236, float addrspace(1)* %arrayidx132
ret void
}