1 //===- LazyBranchProbabilityInfo.cpp - Lazy Branch Probability Analysis ---===//
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 is an alternative analysis pass to BranchProbabilityInfoWrapperPass.
11 // The difference is that with this pass the branch probabilities are not
12 // computed when the analysis pass is executed but rather when the BPI results
13 // is explicitly requested by the analysis client.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/Analysis/LazyBranchProbabilityInfo.h"
18 #include "llvm/Analysis/LoopInfo.h"
19 #include "llvm/Analysis/TargetLibraryInfo.h"
20 #include "llvm/IR/Dominators.h"
21 
22 using namespace llvm;
23 
24 #define DEBUG_TYPE "lazy-branch-prob"
25 
26 INITIALIZE_PASS_BEGIN(LazyBranchProbabilityInfoPass, DEBUG_TYPE,
27                       "Lazy Branch Probability Analysis", true, true)
28 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
29 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
30 INITIALIZE_PASS_END(LazyBranchProbabilityInfoPass, DEBUG_TYPE,
31                     "Lazy Branch Probability Analysis", true, true)
32 
33 char LazyBranchProbabilityInfoPass::ID = 0;
34 
35 LazyBranchProbabilityInfoPass::LazyBranchProbabilityInfoPass()
36     : FunctionPass(ID) {
37   initializeLazyBranchProbabilityInfoPassPass(*PassRegistry::getPassRegistry());
38 }
39 
40 void LazyBranchProbabilityInfoPass::print(raw_ostream &OS,
41                                           const Module *) const {
42   LBPI->getCalculated().print(OS);
43 }
44 
45 void LazyBranchProbabilityInfoPass::getAnalysisUsage(AnalysisUsage &AU) const {
46   // We require DT so it's available when LI is available. The LI updating code
47   // asserts that DT is also present so if we don't make sure that we have DT
48   // here, that assert will trigger.
49   AU.addRequired<DominatorTreeWrapperPass>();
50   AU.addRequired<LoopInfoWrapperPass>();
51   AU.addRequired<TargetLibraryInfoWrapperPass>();
52   AU.setPreservesAll();
53 }
54 
55 void LazyBranchProbabilityInfoPass::releaseMemory() { LBPI.reset(); }
56 
57 bool LazyBranchProbabilityInfoPass::runOnFunction(Function &F) {
58   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
59   TargetLibraryInfo &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
60   LBPI = llvm::make_unique<LazyBranchProbabilityInfo>(&F, &LI, &TLI);
61   return false;
62 }
63 
64 void LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AnalysisUsage &AU) {
65   AU.addRequired<LazyBranchProbabilityInfoPass>();
66   AU.addRequired<LoopInfoWrapperPass>();
67   AU.addRequired<TargetLibraryInfoWrapperPass>();
68 }
69 
70 void llvm::initializeLazyBPIPassPass(PassRegistry &Registry) {
71   INITIALIZE_PASS_DEPENDENCY(LazyBranchProbabilityInfoPass);
72   INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
73   INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass);
74 }
75