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
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(V: Op0, P: m_ICmp(Pred, L: m_Value(V&: X), R: 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>(Val: V);
35 // We should only be extracting the overflow bit.
36 if (!Extract || !Extract->getIndices().equals(RHS: 1))
37 return false;
38
39 II = dyn_cast<IntrinsicInst>(Val: Extract->getAggregateOperand());
40 if (!II ||
41 !match(V: II, P: m_CombineOr(L: m_Intrinsic<Intrinsic::umul_with_overflow>(),
42 R: m_Intrinsic<Intrinsic::smul_with_overflow>())))
43 return false;
44
45 if (II->getArgOperand(i: 0) == X)
46 XIdx = 0;
47 else if (II->getArgOperand(i: 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(V: Op1, P: m_Not(V: m_Value(V&: NotOp1))) && matchMulOverflowCheck(NotOp1));
59
60 if (!Matched)
61 return false;
62
63 Y = &II->getArgOperandUse(i: !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