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 #include "llvm/Support/CommandLine.h"
22 
23 namespace llvm {
24 class AssumeInst;
25 class Function;
26 class Instruction;
27 class AssumptionCache;
28 class DominatorTree;
29 
30 extern cl::opt<bool> EnableKnowledgeRetention;
31 
32 /// Build a call to llvm.assume to preserve informations that can be derived
33 /// from the given instruction.
34 /// If no information derived from \p I, this call returns null.
35 /// The returned instruction is not inserted anywhere.
36 AssumeInst *buildAssumeFromInst(Instruction *I);
37 
38 /// Calls BuildAssumeFromInst and if the resulting llvm.assume is valid insert
39 /// if before I. This is usually what need to be done to salvage the knowledge
40 /// contained in the instruction I.
41 /// The AssumptionCache must be provided if it is available or the cache may
42 /// become silently be invalid.
43 /// The DominatorTree can optionally be provided to enable cross-block
44 /// reasoning.
45 /// This returns if a change was made.
46 bool salvageKnowledge(Instruction *I, AssumptionCache *AC = nullptr,
47                       DominatorTree *DT = nullptr);
48 
49 /// Build and return a new assume created from the provided knowledge
50 /// if the knowledge in the assume is fully redundant this will return nullptr
51 AssumeInst *buildAssumeFromKnowledge(ArrayRef<RetainedKnowledge> Knowledge,
52                                      Instruction *CtxI,
53                                      AssumptionCache *AC = nullptr,
54                                      DominatorTree *DT = nullptr);
55 
56 /// This pass attempts to minimize the number of assume without loosing any
57 /// information.
58 struct AssumeSimplifyPass : public PassInfoMixin<AssumeSimplifyPass> {
59   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
60 };
61 
62 /// This pass will try to build an llvm.assume for every instruction in the
63 /// function. Its main purpose is testing.
64 struct AssumeBuilderPass : public PassInfoMixin<AssumeBuilderPass> {
65   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
66 };
67 
68 /// canonicalize the RetainedKnowledge RK. it is assumed that RK is part of
69 /// Assume. This will return an empty RetainedKnowledge if the knowledge is
70 /// useless.
71 RetainedKnowledge simplifyRetainedKnowledge(AssumeInst *Assume,
72                                             RetainedKnowledge RK,
73                                             AssumptionCache *AC,
74                                             DominatorTree *DT);
75 
76 } // namespace llvm
77 
78 #endif
79