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/Instructions.h" 16 #include "llvm/IR/PatternMatch.h" 17 18 using namespace llvm; 19 using namespace llvm::PatternMatch; 20 21 bool llvm::isCheckForZeroAndMulWithOverflow(Value *Op0, Value *Op1, bool IsAnd, 22 Use *&Y) { 23 ICmpInst::Predicate 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, 1 33 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 else 50 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 67 bool llvm::isCheckForZeroAndMulWithOverflow(Value *Op0, Value *Op1, 68 bool IsAnd) { 69 Use *Y; 70 return isCheckForZeroAndMulWithOverflow(Op0, Op1, IsAnd, Y); 71 } 72