72 lines · cpp
1//==-- OverflowInstAnalysis.cpp - Utils to fold overflow insts ----*- C++ -*-=//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file holds routines to help analyse overflow instructions10// and fold them into constants or other overflow instructions11//12//===----------------------------------------------------------------------===//13 14#include "llvm/Analysis/OverflowInstAnalysis.h"15#include "llvm/IR/Instructions.h"16#include "llvm/IR/PatternMatch.h"17 18using namespace llvm;19using namespace llvm::PatternMatch;20 21bool llvm::isCheckForZeroAndMulWithOverflow(Value *Op0, Value *Op1, bool IsAnd,22 Use *&Y) {23 CmpPredicate Pred;24 Value *X, *NotOp1;25 int XIdx;26 IntrinsicInst *II;27 28 if (!match(Op0, m_ICmp(Pred, m_Value(X), m_Zero())))29 return false;30 31 /// %Agg = call { i4, i1 } @llvm.[us]mul.with.overflow.i4(i4 %X, i4 %???)32 /// %V = extractvalue { i4, i1 } %Agg, 133 auto matchMulOverflowCheck = [X, &II, &XIdx](Value *V) {34 auto *Extract = dyn_cast<ExtractValueInst>(V);35 // We should only be extracting the overflow bit.36 if (!Extract || !Extract->getIndices().equals(1))37 return false;38 39 II = dyn_cast<IntrinsicInst>(Extract->getAggregateOperand());40 if (!II ||41 !match(II, m_CombineOr(m_Intrinsic<Intrinsic::umul_with_overflow>(),42 m_Intrinsic<Intrinsic::smul_with_overflow>())))43 return false;44 45 if (II->getArgOperand(0) == X)46 XIdx = 0;47 else if (II->getArgOperand(1) == X)48 XIdx = 1;49 else50 return false;51 return true;52 };53 54 bool Matched =55 (IsAnd && Pred == ICmpInst::Predicate::ICMP_NE &&56 matchMulOverflowCheck(Op1)) ||57 (!IsAnd && Pred == ICmpInst::Predicate::ICMP_EQ &&58 match(Op1, m_Not(m_Value(NotOp1))) && matchMulOverflowCheck(NotOp1));59 60 if (!Matched)61 return false;62 63 Y = &II->getArgOperandUse(!XIdx);64 return true;65}66 67bool llvm::isCheckForZeroAndMulWithOverflow(Value *Op0, Value *Op1,68 bool IsAnd) {69 Use *Y;70 return isCheckForZeroAndMulWithOverflow(Op0, Op1, IsAnd, Y);71}72