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remove two trunc xforms that are subsumed by EvaluateInDifferentType.

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The only difference is that EvaluateInDifferentType checks to ensure
they are profitable before doing them :)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92788 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-01-05 22:01:41 +00:00
parent c04d3d37e4
commit c0f79af143
2 changed files with 2 additions and 36 deletions
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36
lib/Transforms/InstCombine/InstCombineCasts.cpp
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@ -628,7 +628,6 @@ Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
return 0;
}
Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
if (Instruction *Result = commonIntCastTransforms(CI))
return Result;
@ -646,41 +645,6 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero);
}
// Optimize trunc(lshr(x, c)) to pull the shift through the truncate.
ConstantInt *ShAmtV = 0;
Value *ShiftOp = 0;
if (Src->hasOneUse() &&
match(Src, m_LShr(m_Value(ShiftOp), m_ConstantInt(ShAmtV)))) {
uint32_t ShAmt = ShAmtV->getLimitedValue(SrcBitWidth);
// Get a mask for the bits shifting in.
APInt Mask(APInt::getLowBitsSet(SrcBitWidth, ShAmt).shl(DestBitWidth));
if (MaskedValueIsZero(ShiftOp, Mask)) {
if (ShAmt >= DestBitWidth) // All zeros.
return ReplaceInstUsesWith(CI, Constant::getNullValue(DestTy));
// Okay, we can shrink this. Truncate the input, then return a new
// shift.
Value *V1 = Builder->CreateTrunc(ShiftOp, DestTy, ShiftOp->getName());
Value *V2 = ConstantExpr::getTrunc(ShAmtV, DestTy);
return BinaryOperator::CreateLShr(V1, V2);
}
}
// Transform trunc(shl(X, C)) -> shl(trunc(X), C)
if (Src->hasOneUse() &&
match(Src, m_Shl(m_Value(ShiftOp), m_ConstantInt(ShAmtV)))) {
uint32_t ShAmt = ShAmtV->getLimitedValue(SrcBitWidth);
if (ShAmt >= DestBitWidth) // All zeros.
return ReplaceInstUsesWith(CI, Constant::getNullValue(DestTy));
// Okay, we can shrink this. Truncate the input, then return a new
// shift.
Value *V1 = Builder->CreateTrunc(ShiftOp, DestTy, ShiftOp->getName());
Value *V2 = ConstantExpr::getTrunc(ShAmtV, DestTy);
return BinaryOperator::CreateShl(V1, V2);
}
return 0;
}

2
test/Transforms/InstCombine/bswap.ll
View File

@ -1,3 +1,5 @@
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
; RUN: opt < %s -instcombine -S | \
; RUN: grep {call.*llvm.bswap} | count 6