1//===-- CmpInstAnalysis.h - Utils to help fold compare 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 compare instructions
10// and fold them into constants or other compare instructions
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_ANALYSIS_CMPINSTANALYSIS_H
15#define LLVM_ANALYSIS_CMPINSTANALYSIS_H
16
17#include "llvm/IR/InstrTypes.h"
18
19namespace llvm {
20  class ICmpInst;
21  class Value;
22
23  /// Encode a icmp predicate into a three bit mask. These bits are carefully
24  /// arranged to allow folding of expressions such as:
25  ///
26  ///      (A < B) | (A > B) --> (A != B)
27  ///
28  /// Note that this is only valid if the first and second predicates have the
29  /// same sign. It is illegal to do: (A u< B) | (A s> B)
30  ///
31  /// Three bits are used to represent the condition, as follows:
32  ///   0  A > B
33  ///   1  A == B
34  ///   2  A < B
35  ///
36  /// <=>  Value  Definition
37  /// 000     0   Always false
38  /// 001     1   A >  B
39  /// 010     2   A == B
40  /// 011     3   A >= B
41  /// 100     4   A <  B
42  /// 101     5   A != B
43  /// 110     6   A <= B
44  /// 111     7   Always true
45  ///
46  unsigned getICmpCode(const ICmpInst *ICI, bool InvertPred = false);
47
48  /// This is the complement of getICmpCode. It turns a predicate code into
49  /// either a constant true or false or the predicate for a new ICmp.
50  /// The sign is passed in to determine which kind of predicate to use in the
51  /// new ICmp instruction.
52  /// Non-NULL return value will be a true or false constant.
53  /// NULL return means a new ICmp is needed. The predicate is output in Pred.
54  Constant *getPredForICmpCode(unsigned Code, bool Sign, Type *OpTy,
55                               CmpInst::Predicate &Pred);
56
57  /// Return true if both predicates match sign or if at least one of them is an
58  /// equality comparison (which is signless).
59  bool predicatesFoldable(CmpInst::Predicate P1, CmpInst::Predicate P2);
60
61  /// Decompose an icmp into the form ((X & Mask) pred 0) if possible. The
62  /// returned predicate is either == or !=. Returns false if decomposition
63  /// fails.
64  bool decomposeBitTestICmp(Value *LHS, Value *RHS, CmpInst::Predicate &Pred,
65                            Value *&X, APInt &Mask,
66                            bool LookThroughTrunc = true);
67
68} // end namespace llvm
69
70#endif
71