1 //===- AssumeBundleBuilder.h - utils to build assume bundles ----*- 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 contain tools to preserve informations. They should be used before
10 // performing a transformation that may move and delete instructions as those
11 // transformation may destroy or worsen information that can be derived from the
12 // IR.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_TRANSFORMS_UTILS_ASSUMEBUNDLEBUILDER_H
17 #define LLVM_TRANSFORMS_UTILS_ASSUMEBUNDLEBUILDER_H
18 
19 #include "llvm/Analysis/AssumeBundleQueries.h"
20 #include "llvm/IR/PassManager.h"
21 
22 namespace llvm {
23 class AssumeInst;
24 class Function;
25 class FunctionPass;
26 class Instruction;
27 class AssumptionCache;
28 class DominatorTree;
29 
30 /// Build a call to llvm.assume to preserve informations that can be derived
31 /// from the given instruction.
32 /// If no information derived from \p I, this call returns null.
33 /// The returned instruction is not inserted anywhere.
34 AssumeInst *buildAssumeFromInst(Instruction *I);
35 
36 /// Calls BuildAssumeFromInst and if the resulting llvm.assume is valid insert
37 /// if before I. This is usually what need to be done to salvage the knowledge
38 /// contained in the instruction I.
39 /// The AssumptionCache must be provided if it is available or the cache may
40 /// become silently be invalid.
41 /// The DominatorTree can optionally be provided to enable cross-block
42 /// reasoning.
43 void salvageKnowledge(Instruction *I, AssumptionCache *AC = nullptr,
44                       DominatorTree *DT = nullptr);
45 
46 /// Build and return a new assume created from the provided knowledge
47 /// if the knowledge in the assume is fully redundant this will return nullptr
48 AssumeInst *buildAssumeFromKnowledge(ArrayRef<RetainedKnowledge> Knowledge,
49                                      Instruction *CtxI,
50                                      AssumptionCache *AC = nullptr,
51                                      DominatorTree *DT = nullptr);
52 
53 /// This pass attempts to minimize the number of assume without loosing any
54 /// information.
55 struct AssumeSimplifyPass : public PassInfoMixin<AssumeSimplifyPass> {
56   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
57 };
58 
59 FunctionPass *createAssumeSimplifyPass();
60 
61 /// This pass will try to build an llvm.assume for every instruction in the
62 /// function. Its main purpose is testing.
63 struct AssumeBuilderPass : public PassInfoMixin<AssumeBuilderPass> {
64   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
65 };
66 
67 /// canonicalize the RetainedKnowledge RK. it is assumed that RK is part of
68 /// Assume. This will return an empty RetainedKnowledge if the knowledge is
69 /// useless.
70 RetainedKnowledge simplifyRetainedKnowledge(AssumeInst *Assume,
71                                             RetainedKnowledge RK,
72                                             AssumptionCache *AC,
73                                             DominatorTree *DT);
74 
75 } // namespace llvm
76 
77 #endif
78