[llvm-commits] [llvm] r125451 - in /llvm/trunk/lib/Transforms/InstCombine: InstCombine.h InstCombineCompares.cpp
Chris Lattner
sabre at nondot.org
Sat Feb 12 23:43:07 PST 2011
Author: lattner
Date: Sun Feb 13 01:43:07 2011
New Revision: 125451
URL: http://llvm.org/viewvc/llvm-project?rev=125451&view=rev
Log:
refactor some code out into a helper method.
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombine.h
llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombine.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombine.h?rev=125451&r1=125450&r2=125451&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombine.h (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombine.h Sun Feb 13 01:43:07 2011
@@ -145,6 +145,8 @@
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,
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=125451&r1=125450&r2=125451&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Sun Feb 13 01:43:07 2011
@@ -928,6 +928,55 @@
}
}
+/// 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 @@
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 @@
}
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:
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