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Fix missed optimization opportunity when analyzing cast of mul and select.

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llvm-svn: 53151
This commit is contained in:
Nick Lewycky 2008-07-05 21:19:34 +00:00
parent a43d6758ac
commit 94f9c5a42e
2 changed files with 43 additions and 9 deletions
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23
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -6917,6 +6917,7 @@ bool InstCombiner::CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
switch (I->getOpcode()) {
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
@ -6926,14 +6927,6 @@ bool InstCombiner::CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
NumCastsRemoved);
case Instruction::Mul:
// A multiply can be truncated by truncating its operands.
return Ty->getBitWidth() < OrigTy->getBitWidth() &&
CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
NumCastsRemoved) &&
CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
NumCastsRemoved);
case Instruction::Shl:
// If we are truncating the result of this SHL, and if it's a shift of a
// constant amount, we can always perform a SHL in a smaller type.
@ -6970,7 +6963,13 @@ bool InstCombiner::CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
if (I->getOpcode() == CastOpc)
return true;
break;
case Instruction::Select: {
SelectInst *SI = cast<SelectInst>(I);
return CanEvaluateInDifferentType(SI->getTrueValue(), Ty, CastOpc,
NumCastsRemoved) &&
CanEvaluateInDifferentType(SI->getFalseValue(), Ty, CastOpc,
NumCastsRemoved);
}
case Instruction::PHI: {
// We can change a phi if we can change all operands.
PHINode *PN = cast<PHINode>(I);
@ -7028,6 +7027,12 @@ Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty,
Res = CastInst::Create(cast<CastInst>(I)->getOpcode(), I->getOperand(0),
Ty);
break;
case Instruction::Select: {
Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned);
Res = SelectInst::Create(I->getOperand(0), True, False);
break;
}
case Instruction::PHI: {
PHINode *OPN = cast<PHINode>(I);
PHINode *NPN = PHINode::Create(Ty);

29
test/Transforms/InstCombine/cast-mul-select.ll Normal file
View File

@ -0,0 +1,29 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | notcast
define i32 @mul(i32 %x, i32 %y) {
%A = trunc i32 %x to i8
%B = trunc i32 %y to i8
%C = mul i8 %A, %B
%D = zext i8 %C to i32
ret i32 %D
}
define i32 @select1(i1 %cond, i32 %x, i32 %y, i32 %z) {
%A = trunc i32 %x to i8
%B = trunc i32 %y to i8
%C = trunc i32 %z to i8
%D = add i8 %A, %B
%E = select i1 %cond, i8 %C, i8 %D
%F = zext i8 %E to i32
ret i32 %F
}
define i8 @select2(i1 %cond, i8 %x, i8 %y, i8 %z) {
%A = zext i8 %x to i32
%B = zext i8 %y to i32
%C = zext i8 %z to i32
%D = add i32 %A, %B
%E = select i1 %cond, i32 %C, i32 %D
%F = trunc i32 %E to i8
ret i8 %F
}