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Generalize the zext(trunc(t) & C) instcombine to work even with 

C is not a low-bits mask, and add a similar instcombine for
zext((trunc(t) & C) ^ C).

llvm-svn: 73705
This commit is contained in:
Dan Gohman 2009-06-18 16:30:21 +00:00
parent 5a728c908c
commit 56bd02c55c
2 changed files with 37 additions and 9 deletions
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29
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -8564,20 +8564,33 @@ Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
} }
} }
// zext(trunc(t) & C) -> (t & C) if C is a mask. // zext(trunc(t) & C) -> (t & zext(C)).
if (SrcI && SrcI->getOpcode() == Instruction::And && SrcI->hasOneUse()) if (SrcI && SrcI->getOpcode() == Instruction::And && SrcI->hasOneUse())
if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1))) if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1)))
if (TruncInst *TI = dyn_cast<TruncInst>(SrcI->getOperand(0))) { if (TruncInst *TI = dyn_cast<TruncInst>(SrcI->getOperand(0))) {
Value *TI0 = TI->getOperand(0); Value *TI0 = TI->getOperand(0);
if (TI0->getType() == CI.getType()) { if (TI0->getType() == CI.getType())
unsigned TO = C->getValue().countTrailingOnes(); return
if (APIntOps::isMask(TO, C->getValue())) BinaryOperator::CreateAnd(TI0,
return ConstantExpr::getZExt(C, CI.getType()));
BinaryOperator::Create(Instruction::And, TI0,
ConstantExpr::getZExt(C, CI.getType()));
}
} }
// zext((trunc(t) & C) ^ C) -> ((t & zext(C)) ^ zext(C)).
if (SrcI && SrcI->getOpcode() == Instruction::Xor && SrcI->hasOneUse())
if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1)))
if (BinaryOperator *And = dyn_cast<BinaryOperator>(SrcI->getOperand(0)))
if (And->getOpcode() == Instruction::And && And->hasOneUse() &&
And->getOperand(1) == C)
if (TruncInst *TI = dyn_cast<TruncInst>(And->getOperand(0))) {
Value *TI0 = TI->getOperand(0);
if (TI0->getType() == CI.getType()) {
Constant *ZC = ConstantExpr::getZExt(C, CI.getType());
Instruction *NewAnd = BinaryOperator::CreateAnd(TI0, ZC, "tmp");
InsertNewInstBefore(NewAnd, *And);
return BinaryOperator::CreateXor(NewAnd, ZC);
}
}
return 0; return 0;
} }

17
llvm/test/Transforms/InstCombine/trunc-mask-ext.ll
View File

@ -2,7 +2,7 @@
; RUN: not grep zext %t ; RUN: not grep zext %t
; RUN: not grep sext %t ; RUN: not grep sext %t
; Instcombine should be able to eliminate both ext casts. ; Instcombine should be able to eliminate all of these ext casts.
declare void @use(i32) declare void @use(i32)
@ -21,3 +21,18 @@ define i64 @bar(i64 %a) {
call void @use(i32 %b) call void @use(i32 %b)
ret i64 %d ret i64 %d
} }
define i64 @goo(i64 %a) {
%b = trunc i64 %a to i32
%c = and i32 %b, 8
%d = zext i32 %c to i64
call void @use(i32 %b)
ret i64 %d
}
define i64 @hoo(i64 %a) {
%b = trunc i64 %a to i32
%c = and i32 %b, 8
%x = xor i32 %c, 8
%d = zext i32 %x to i64
call void @use(i32 %b)
ret i64 %d
}