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