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//===- CmpInstAnalysis.cpp - Utils to help fold compares ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file holds routines to help analyse compare instructions
// and fold them into constants or other compare instructions
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/CmpInstAnalysis.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/PatternMatch.h"
using namespace llvm;
unsigned llvm::getICmpCode(const ICmpInst *ICI, bool InvertPred) {
ICmpInst::Predicate Pred = InvertPred ? ICI->getInversePredicate()
: ICI->getPredicate();
switch (Pred) {
// False -> 0
case ICmpInst::ICMP_UGT: return 1; // 001
case ICmpInst::ICMP_SGT: return 1; // 001
case ICmpInst::ICMP_EQ: return 2; // 010
case ICmpInst::ICMP_UGE: return 3; // 011
case ICmpInst::ICMP_SGE: return 3; // 011
case ICmpInst::ICMP_ULT: return 4; // 100
case ICmpInst::ICMP_SLT: return 4; // 100
case ICmpInst::ICMP_NE: return 5; // 101
case ICmpInst::ICMP_ULE: return 6; // 110
case ICmpInst::ICMP_SLE: return 6; // 110
// True -> 7
default:
llvm_unreachable("Invalid ICmp predicate!");
}
}
Value *llvm::getICmpValue(bool Sign, unsigned Code, Value *LHS, Value *RHS,
CmpInst::Predicate &NewICmpPred) {
switch (Code) {
default: llvm_unreachable("Illegal ICmp code!");
case 0: // False.
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
case 1: NewICmpPred = Sign ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; break;
case 2: NewICmpPred = ICmpInst::ICMP_EQ; break;
case 3: NewICmpPred = Sign ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; break;
case 4: NewICmpPred = Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; break;
case 5: NewICmpPred = ICmpInst::ICMP_NE; break;
case 6: NewICmpPred = Sign ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; break;
case 7: // True.
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 1);
}
return nullptr;
}
bool llvm::PredicatesFoldable(ICmpInst::Predicate p1, ICmpInst::Predicate p2) {
return (CmpInst::isSigned(p1) == CmpInst::isSigned(p2)) ||
(CmpInst::isSigned(p1) && ICmpInst::isEquality(p2)) ||
(CmpInst::isSigned(p2) && ICmpInst::isEquality(p1));
}
bool llvm::decomposeBitTestICmp(Value *LHS, Value *RHS,
CmpInst::Predicate &Pred,
Value *&X, APInt &Mask, bool LookThruTrunc) {
using namespace PatternMatch;
const APInt *C;
if (!match(RHS, m_APInt(C)))
return false;
switch (Pred) {
default:
return false;
case ICmpInst::ICMP_SLT:
// X < 0 is equivalent to (X & SignMask) != 0.
if (!C->isNullValue())
return false;
Mask = APInt::getSignMask(C->getBitWidth());
Pred = ICmpInst::ICMP_NE;
break;
case ICmpInst::ICMP_SLE:
// X <= -1 is equivalent to (X & SignMask) != 0.
if (!C->isAllOnesValue())
return false;
Mask = APInt::getSignMask(C->getBitWidth());
Pred = ICmpInst::ICMP_NE;
break;
case ICmpInst::ICMP_SGT:
// X > -1 is equivalent to (X & SignMask) == 0.
if (!C->isAllOnesValue())
return false;
Mask = APInt::getSignMask(C->getBitWidth());
Pred = ICmpInst::ICMP_EQ;
break;
case ICmpInst::ICMP_SGE:
// X >= 0 is equivalent to (X & SignMask) == 0.
if (!C->isNullValue())
return false;
Mask = APInt::getSignMask(C->getBitWidth());
Pred = ICmpInst::ICMP_EQ;
break;
case ICmpInst::ICMP_ULT:
// X <u 2^n is equivalent to (X & ~(2^n-1)) == 0.
if (!C->isPowerOf2())
return false;
Mask = -*C;
Pred = ICmpInst::ICMP_EQ;
break;
case ICmpInst::ICMP_ULE:
// X <=u 2^n-1 is equivalent to (X & ~(2^n-1)) == 0.
if (!(*C + 1).isPowerOf2())
return false;
Mask = ~*C;
Pred = ICmpInst::ICMP_EQ;
break;
case ICmpInst::ICMP_UGT:
// X >u 2^n-1 is equivalent to (X & ~(2^n-1)) != 0.
if (!(*C + 1).isPowerOf2())
return false;
Mask = ~*C;
Pred = ICmpInst::ICMP_NE;
break;
case ICmpInst::ICMP_UGE:
// X >=u 2^n is equivalent to (X & ~(2^n-1)) != 0.
if (!C->isPowerOf2())
return false;
Mask = -*C;
Pred = ICmpInst::ICMP_NE;
break;
}
if (LookThruTrunc && match(LHS, m_Trunc(m_Value(X)))) {
Mask = Mask.zext(X->getType()->getScalarSizeInBits());
} else {
X = LHS;
}
return true;
}
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