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-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file holds routines to help analyse overflow instructions 10 // and fold them into constants or other overflow instructions 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Analysis/OverflowInstAnalysis.h" 15 #include "llvm/IR/Constants.h" 16 #include "llvm/IR/Instructions.h" 17 #include "llvm/IR/PatternMatch.h" 18 19 using namespace llvm; 20 using namespace llvm::PatternMatch; 21 22 bool llvm::isCheckForZeroAndMulWithOverflow(Value *Op0, Value *Op1, bool IsAnd, 23 Use *&Y) { 24 ICmpInst::Predicate Pred; 25 Value *X, *NotOp1; 26 int XIdx; 27 IntrinsicInst *II; 28 29 if (!match(Op0, m_ICmp(Pred, m_Value(X), m_Zero()))) 30 return false; 31 32 /// %Agg = call { i4, i1 } @llvm.[us]mul.with.overflow.i4(i4 %X, i4 %???) 33 /// %V = extractvalue { i4, i1 } %Agg, 1 34 auto matchMulOverflowCheck = [X, &II, &XIdx](Value *V) { 35 auto *Extract = dyn_cast<ExtractValueInst>(V); 36 // We should only be extracting the overflow bit. 37 if (!Extract || !Extract->getIndices().equals(1)) 38 return false; 39 40 II = dyn_cast<IntrinsicInst>(Extract->getAggregateOperand()); 41 if (!II || 42 !match(II, m_CombineOr(m_Intrinsic<Intrinsic::umul_with_overflow>(), 43 m_Intrinsic<Intrinsic::smul_with_overflow>()))) 44 return false; 45 46 if (II->getArgOperand(0) == X) 47 XIdx = 0; 48 else if (II->getArgOperand(1) == X) 49 XIdx = 1; 50 else 51 return false; 52 return true; 53 }; 54 55 bool Matched = 56 (IsAnd && Pred == ICmpInst::Predicate::ICMP_NE && 57 matchMulOverflowCheck(Op1)) || 58 (!IsAnd && Pred == ICmpInst::Predicate::ICMP_EQ && 59 match(Op1, m_Not(m_Value(NotOp1))) && matchMulOverflowCheck(NotOp1)); 60 61 if (!Matched) 62 return false; 63 64 Y = &II->getArgOperandUse(!XIdx); 65 return true; 66 } 67 68 bool llvm::isCheckForZeroAndMulWithOverflow(Value *Op0, Value *Op1, 69 bool IsAnd) { 70 Use *Y; 71 return isCheckForZeroAndMulWithOverflow(Op0, Op1, IsAnd, Y); 72 } 73