1 //===- InstCombine.h - InstCombine pass -------------------------*- 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 /// \file
9 ///
10 /// This file provides the primary interface to the instcombine pass. This pass
11 /// is suitable for use in the new pass manager. For a pass that works with the
12 /// legacy pass manager, use \c createInstructionCombiningPass().
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_TRANSFORMS_INSTCOMBINE_INSTCOMBINE_H
17 #define LLVM_TRANSFORMS_INSTCOMBINE_INSTCOMBINE_H
18 
19 #include "llvm/IR/Function.h"
20 #include "llvm/IR/PassManager.h"
21 #include "llvm/Pass.h"
22 
23 #define DEBUG_TYPE "instcombine"
24 #include "llvm/Transforms/Utils/InstructionWorklist.h"
25 
26 namespace llvm {
27 
28 static constexpr unsigned InstCombineDefaultMaxIterations = 1;
29 
30 struct InstCombineOptions {
31   bool UseLoopInfo = false;
32   // Verify that a fix point has been reached after MaxIterations.
33   bool VerifyFixpoint = false;
34   unsigned MaxIterations = InstCombineDefaultMaxIterations;
35 
36   InstCombineOptions() = default;
37 
setUseLoopInfoInstCombineOptions38   InstCombineOptions &setUseLoopInfo(bool Value) {
39     UseLoopInfo = Value;
40     return *this;
41   }
42 
setVerifyFixpointInstCombineOptions43   InstCombineOptions &setVerifyFixpoint(bool Value) {
44     VerifyFixpoint = Value;
45     return *this;
46   }
47 
setMaxIterationsInstCombineOptions48   InstCombineOptions &setMaxIterations(unsigned Value) {
49     MaxIterations = Value;
50     return *this;
51   }
52 };
53 
54 class InstCombinePass : public PassInfoMixin<InstCombinePass> {
55 private:
56   InstructionWorklist Worklist;
57   InstCombineOptions Options;
58 
59 public:
60   explicit InstCombinePass(InstCombineOptions Opts = {});
61   void printPipeline(raw_ostream &OS,
62                      function_ref<StringRef(StringRef)> MapClassName2PassName);
63 
64   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
65 };
66 
67 /// The legacy pass manager's instcombine pass.
68 ///
69 /// This is a basic whole-function wrapper around the instcombine utility. It
70 /// will try to combine all instructions in the function.
71 class InstructionCombiningPass : public FunctionPass {
72   InstructionWorklist Worklist;
73 
74 public:
75   static char ID; // Pass identification, replacement for typeid
76 
77   explicit InstructionCombiningPass();
78 
79   void getAnalysisUsage(AnalysisUsage &AU) const override;
80   bool runOnFunction(Function &F) override;
81 };
82 
83 //===----------------------------------------------------------------------===//
84 //
85 // InstructionCombining - Combine instructions to form fewer, simple
86 // instructions. This pass does not modify the CFG, and has a tendency to make
87 // instructions dead, so a subsequent DCE pass is useful.
88 //
89 // This pass combines things like:
90 //    %Y = add int 1, %X
91 //    %Z = add int 1, %Y
92 // into:
93 //    %Z = add int 2, %X
94 //
95 FunctionPass *createInstructionCombiningPass();
96 }
97 
98 #undef DEBUG_TYPE
99 
100 #endif
101