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 Instruction;
26 class AssumptionCache;
27 class DominatorTree;
28 
29 /// Build a call to llvm.assume to preserve informations that can be derived
30 /// from the given instruction.
31 /// If no information derived from \p I, this call returns null.
32 /// The returned instruction is not inserted anywhere.
33 AssumeInst *buildAssumeFromInst(Instruction *I);
34 
35 /// Calls BuildAssumeFromInst and if the resulting llvm.assume is valid insert
36 /// if before I. This is usually what need to be done to salvage the knowledge
37 /// contained in the instruction I.
38 /// The AssumptionCache must be provided if it is available or the cache may
39 /// become silently be invalid.
40 /// The DominatorTree can optionally be provided to enable cross-block
41 /// reasoning.
42 /// This returns if a change was made.
43 bool 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 /// This pass will try to build an llvm.assume for every instruction in the
60 /// function. Its main purpose is testing.
61 struct AssumeBuilderPass : public PassInfoMixin<AssumeBuilderPass> {
62   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
63 };
64 
65 /// canonicalize the RetainedKnowledge RK. it is assumed that RK is part of
66 /// Assume. This will return an empty RetainedKnowledge if the knowledge is
67 /// useless.
68 RetainedKnowledge simplifyRetainedKnowledge(AssumeInst *Assume,
69                                             RetainedKnowledge RK,
70                                             AssumptionCache *AC,
71                                             DominatorTree *DT);
72 
73 } // namespace llvm
74 
75 #endif
76