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move a trunc-specific xform out of commonIntCastTransforms into visitTrunc

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92768 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-01-05 20:57:30 +00:00
parent 3168c7dd25
commit f86d799a29
1 changed files with 25 additions and 16 deletions
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41
lib/Transforms/InstCombine/InstCombineCasts.cpp
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@ -28,19 +28,25 @@ static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
Offset = CI->getZExtValue(); Offset = CI->getZExtValue();
Scale = 0; Scale = 0;
return ConstantInt::get(Type::getInt32Ty(Val->getContext()), 0); return ConstantInt::get(Type::getInt32Ty(Val->getContext()), 0);
} else if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) { }
if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) { if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
if (I->getOpcode() == Instruction::Shl) { if (I->getOpcode() == Instruction::Shl) {
// This is a value scaled by '1 << the shift amt'. // This is a value scaled by '1 << the shift amt'.
Scale = 1U << RHS->getZExtValue(); Scale = 1U << RHS->getZExtValue();
Offset = 0; Offset = 0;
return I->getOperand(0); return I->getOperand(0);
} else if (I->getOpcode() == Instruction::Mul) { }
if (I->getOpcode() == Instruction::Mul) {
// This value is scaled by 'RHS'. // This value is scaled by 'RHS'.
Scale = RHS->getZExtValue(); Scale = RHS->getZExtValue();
Offset = 0; Offset = 0;
return I->getOperand(0); return I->getOperand(0);
} else if (I->getOpcode() == Instruction::Add) { }
if (I->getOpcode() == Instruction::Add) {
// We have X+C. Check to see if we really have (X*C2)+C1, // We have X+C. Check to see if we really have (X*C2)+C1,
// where C1 is divisible by C2. // where C1 is divisible by C2.
unsigned SubScale; unsigned SubScale;
@ -650,18 +656,6 @@ Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
ConstantInt::get(CI.getType(), 1)); ConstantInt::get(CI.getType(), 1));
} }
break; break;
case Instruction::Shl: {
// Canonicalize trunc inside shl, if we can.
ConstantInt *CI = dyn_cast<ConstantInt>(Op1);
if (CI && DestBitSize < SrcBitSize &&
CI->getLimitedValue(DestBitSize) < DestBitSize) {
Value *Op0c = Builder->CreateTrunc(Op0, DestTy, Op0->getName());
Value *Op1c = Builder->CreateTrunc(Op1, DestTy, Op1->getName());
return BinaryOperator::CreateShl(Op0c, Op1c);
}
break;
}
} }
return 0; return 0;
} }
@ -684,7 +678,7 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero); return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero);
} }
// Optimize trunc(lshr(), c) to pull the shift through the truncate. // Optimize trunc(lshr(x, c)) to pull the shift through the truncate.
ConstantInt *ShAmtV = 0; ConstantInt *ShAmtV = 0;
Value *ShiftOp = 0; Value *ShiftOp = 0;
if (Src->hasOneUse() && if (Src->hasOneUse() &&
@ -704,6 +698,21 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
return BinaryOperator::CreateLShr(V1, V2); 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(Ty));
// Okay, we can shrink this. Truncate the input, then return a new
// shift.
Value *V1 = Builder->CreateTrunc(ShiftOp, Ty, ShiftOp->getName());
Value *V2 = ConstantExpr::getTrunc(ShAmtV, Ty);
return BinaryOperator::CreateShl(V1, V2);
}
return 0; return 0;
} }