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refactor some code out into a helper method.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125451 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2011-02-13 07:43:07 +00:00
parent 8ebaf90958
commit 74542aa500
2 changed files with 56 additions and 46 deletions
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2
lib/Transforms/InstCombine/InstCombine.h
View File

@ -145,6 +145,8 @@ public:
ConstantInt *RHS);
Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
ConstantInt *DivRHS);
Instruction *FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *DivI,
ConstantInt *DivRHS);
Instruction *FoldICmpAddOpCst(ICmpInst &ICI, Value *X, ConstantInt *CI,
ICmpInst::Predicate Pred, Value *TheAdd);
Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,

100
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -928,6 +928,55 @@ Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
}
}
/// FoldICmpShrCst - Handle "icmp(([al]shr X, cst1), cst2)".
Instruction *InstCombiner::FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *Shr,
ConstantInt *ShAmt) {
if (!ICI.isEquality()) return 0;
const APInt &CmpRHSV = cast<ConstantInt>(ICI.getOperand(1))->getValue();
// Check that the shift amount is in range. If not, don't perform
// undefined shifts. When the shift is visited it will be
// simplified.
uint32_t TypeBits = CmpRHSV.getBitWidth();
uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
if (ShAmtVal >= TypeBits)
return 0;
// If we are comparing against bits always shifted out, the
// comparison cannot succeed.
APInt Comp = CmpRHSV << ShAmtVal;
ConstantInt *ShiftedCmpRHS = ConstantInt::get(ICI.getContext(), Comp);
if (Shr->getOpcode() == Instruction::LShr)
Comp = Comp.lshr(ShAmtVal);
else
Comp = Comp.ashr(ShAmtVal);
if (Comp != CmpRHSV) { // Comparing against a bit that we know is zero.
bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
Constant *Cst = ConstantInt::get(Type::getInt1Ty(ICI.getContext()),
IsICMP_NE);
return ReplaceInstUsesWith(ICI, Cst);
}
// Otherwise, check to see if the bits shifted out are known to be zero.
// If so, we can compare against the unshifted value:
// (X & 4) >> 1 == 2 --> (X & 4) == 4.
if (Shr->hasOneUse() && cast<BinaryOperator>(Shr)->isExact())
return new ICmpInst(ICI.getPredicate(), Shr->getOperand(0), ShiftedCmpRHS);
if (Shr->hasOneUse()) {
// Otherwise strength reduce the shift into an and.
APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
Constant *Mask = ConstantInt::get(ICI.getContext(), Val);
Value *And = Builder->CreateAnd(Shr->getOperand(0),
Mask, Shr->getName()+".mask");
return new ICmpInst(ICI.getPredicate(), And, ShiftedCmpRHS);
}
return 0;
}
/// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)".
///
@ -1153,7 +1202,6 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
if (match(LHSI, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
// Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
// -> and (icmp eq P, null), (icmp eq Q, null).
Value *ICIP = Builder->CreateICmp(ICI.getPredicate(), P,
Constant::getNullValue(P->getType()));
Value *ICIQ = Builder->CreateICmp(ICI.getPredicate(), Q,
@ -1229,53 +1277,13 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
}
case Instruction::LShr: // (icmp pred (shr X, ShAmt), CI)
case Instruction::AShr: {
case Instruction::AShr:
// Only handle equality comparisons of shift-by-constant.
ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1));
if (!ShAmt || !ICI.isEquality()) break;
// Check that the shift amount is in range. If not, don't perform
// undefined shifts. When the shift is visited it will be
// simplified.
uint32_t TypeBits = RHSV.getBitWidth();
uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
if (ShAmtVal >= TypeBits)
break;
// If we are comparing against bits always shifted out, the
// comparison cannot succeed.
APInt Comp = RHSV << ShAmtVal;
if (LHSI->getOpcode() == Instruction::LShr)
Comp = Comp.lshr(ShAmtVal);
else
Comp = Comp.ashr(ShAmtVal);
if (Comp != RHSV) { // Comparing against a bit that we know is zero.
bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
Constant *Cst = ConstantInt::get(Type::getInt1Ty(ICI.getContext()),
IsICMP_NE);
return ReplaceInstUsesWith(ICI, Cst);
}
// Otherwise, check to see if the bits shifted out are known to be zero.
// If so, we can compare against the unshifted value:
// (X & 4) >> 1 == 2 --> (X & 4) == 4.
if (LHSI->hasOneUse() && cast<BinaryOperator>(LHSI)->isExact())
return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0),
ConstantExpr::getShl(RHS, ShAmt));
if (LHSI->hasOneUse()) {
// Otherwise strength reduce the shift into an and.
APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
Constant *Mask = ConstantInt::get(ICI.getContext(), Val);
Value *And = Builder->CreateAnd(LHSI->getOperand(0),
Mask, LHSI->getName()+".mask");
return new ICmpInst(ICI.getPredicate(), And,
ConstantExpr::getShl(RHS, ShAmt));
}
if (ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1)))
if (Instruction *Res = FoldICmpShrCst(ICI, cast<BinaryOperator>(LHSI),
ShAmt))
return Res;
break;
}
case Instruction::SDiv:
case Instruction::UDiv: