1 //===- AggressiveInstCombine.cpp ------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the aggressive expression pattern combiner classes.
11 // Currently, it handles expression patterns for:
12 //  * Truncate instruction
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "llvm/Transforms/AggressiveInstCombine/AggressiveInstCombine.h"
17 #include "AggressiveInstCombineInternal.h"
18 #include "llvm/Analysis/AliasAnalysis.h"
19 #include "llvm/Analysis/BasicAliasAnalysis.h"
20 #include "llvm/Analysis/GlobalsModRef.h"
21 #include "llvm/Analysis/TargetLibraryInfo.h"
22 #include "llvm/IR/DataLayout.h"
23 #include "llvm/Pass.h"
24 #include "llvm/Transforms/Scalar.h"
25 using namespace llvm;
26 
27 #define DEBUG_TYPE "aggressive-instcombine"
28 
29 namespace {
30 /// Contains expression pattern combiner logic.
31 /// This class provides both the logic to combine expression patterns and
32 /// combine them. It differs from InstCombiner class in that each pattern
33 /// combiner runs only once as opposed to InstCombine's multi-iteration,
34 /// which allows pattern combiner to have higher complexity than the O(1)
35 /// required by the instruction combiner.
36 class AggressiveInstCombinerLegacyPass : public FunctionPass {
37 public:
38   static char ID; // Pass identification, replacement for typeid
39 
40   AggressiveInstCombinerLegacyPass() : FunctionPass(ID) {
41     initializeAggressiveInstCombinerLegacyPassPass(
42         *PassRegistry::getPassRegistry());
43   }
44 
45   void getAnalysisUsage(AnalysisUsage &AU) const override;
46 
47   /// Run all expression pattern optimizations on the given /p F function.
48   ///
49   /// \param F function to optimize.
50   /// \returns true if the IR is changed.
51   bool runOnFunction(Function &F) override;
52 };
53 } // namespace
54 
55 void AggressiveInstCombinerLegacyPass::getAnalysisUsage(
56     AnalysisUsage &AU) const {
57   AU.setPreservesCFG();
58   AU.addRequired<TargetLibraryInfoWrapperPass>();
59   AU.addPreserved<AAResultsWrapperPass>();
60   AU.addPreserved<BasicAAWrapperPass>();
61   AU.addPreserved<GlobalsAAWrapperPass>();
62 }
63 
64 bool AggressiveInstCombinerLegacyPass::runOnFunction(Function &F) {
65   auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
66   auto &DL = F.getParent()->getDataLayout();
67 
68   bool MadeIRChange = false;
69 
70   // Handle TruncInst patterns
71   TruncInstCombine TIC(TLI, DL);
72   MadeIRChange |= TIC.run(F);
73 
74   // TODO: add more patterns to handle...
75 
76   return MadeIRChange;
77 }
78 
79 PreservedAnalyses AggressiveInstCombinePass::run(Function &F,
80                                                  FunctionAnalysisManager &AM) {
81   auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
82   auto &DL = F.getParent()->getDataLayout();
83   bool MadeIRChange = false;
84 
85   // Handle TruncInst patterns
86   TruncInstCombine TIC(TLI, DL);
87   MadeIRChange |= TIC.run(F);
88   if (!MadeIRChange)
89     // No changes, all analyses are preserved.
90     return PreservedAnalyses::all();
91 
92   // Mark all the analyses that instcombine updates as preserved.
93   PreservedAnalyses PA;
94   PA.preserveSet<CFGAnalyses>();
95   PA.preserve<AAManager>();
96   PA.preserve<GlobalsAA>();
97   return PA;
98 }
99 
100 char AggressiveInstCombinerLegacyPass::ID = 0;
101 INITIALIZE_PASS_BEGIN(AggressiveInstCombinerLegacyPass,
102                       "aggressive-instcombine",
103                       "Combine pattern based expressions", false, false)
104 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
105 INITIALIZE_PASS_END(AggressiveInstCombinerLegacyPass, "aggressive-instcombine",
106                     "Combine pattern based expressions", false, false)
107 
108 FunctionPass *llvm::createAggressiveInstCombinerPass() {
109   return new AggressiveInstCombinerLegacyPass();
110 }
111