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 class InstCombinePass : public PassInfoMixin<InstCombinePass> {
29   InstructionWorklist Worklist;
30   const unsigned MaxIterations;
31 
32 public:
33   explicit InstCombinePass();
34   explicit InstCombinePass(unsigned MaxIterations);
35 
36   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
37 };
38 
39 /// The legacy pass manager's instcombine pass.
40 ///
41 /// This is a basic whole-function wrapper around the instcombine utility. It
42 /// will try to combine all instructions in the function.
43 class InstructionCombiningPass : public FunctionPass {
44   InstructionWorklist Worklist;
45   const unsigned MaxIterations;
46 
47 public:
48   static char ID; // Pass identification, replacement for typeid
49 
50   explicit InstructionCombiningPass();
51   explicit InstructionCombiningPass(unsigned MaxIterations);
52 
53   void getAnalysisUsage(AnalysisUsage &AU) const override;
54   bool runOnFunction(Function &F) override;
55 };
56 
57 //===----------------------------------------------------------------------===//
58 //
59 // InstructionCombining - Combine instructions to form fewer, simple
60 // instructions. This pass does not modify the CFG, and has a tendency to make
61 // instructions dead, so a subsequent DCE pass is useful.
62 //
63 // This pass combines things like:
64 //    %Y = add int 1, %X
65 //    %Z = add int 1, %Y
66 // into:
67 //    %Z = add int 2, %X
68 //
69 FunctionPass *createInstructionCombiningPass();
70 FunctionPass *createInstructionCombiningPass(unsigned MaxIterations);
71 }
72 
73 #undef DEBUG_TYPE
74 
75 #endif
76