1//===- StaticDataAnnotator - Annotate static data's section prefix --------===//
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// To reason about module-wide data hotness in a module granularity, this file
10// implements a module pass StaticDataAnnotator to work coordinately with the
11// StaticDataSplitter pass.
12//
13// The StaticDataSplitter pass is a machine function pass. It analyzes data
14// hotness based on code and adds counters in StaticDataProfileInfo via its
15// wrapper pass StaticDataProfileInfoWrapper.
16// The StaticDataProfileInfoWrapper sits in the middle between the
17// StaticDataSplitter and StaticDataAnnotator passes.
18// The StaticDataAnnotator pass is a module pass. It iterates global variables
19// in the module, looks up counters from StaticDataProfileInfo and sets the
20// section prefix based on profiles.
21//
22// The three-pass structure is implemented for practical reasons, to work around
23// the limitation that a module pass based on legacy pass manager cannot make
24// use of MachineBlockFrequencyInfo analysis. In the future, we can consider
25// porting the StaticDataSplitter pass to a module-pass using the new pass
26// manager framework. That way, analysis are lazily computed as opposed to
27// eagerly scheduled, and a module pass can use MachineBlockFrequencyInfo.
28//===----------------------------------------------------------------------===//
29
30#include "llvm/CodeGen/StaticDataAnnotator.h"
31#include "llvm/Analysis/ProfileSummaryInfo.h"
32#include "llvm/Analysis/StaticDataProfileInfo.h"
33#include "llvm/CodeGen/Passes.h"
34#include "llvm/IR/Analysis.h"
35#include "llvm/IR/Module.h"
36#include "llvm/IR/PassManager.h"
37#include "llvm/InitializePasses.h"
38#include "llvm/Pass.h"
39
40#define DEBUG_TYPE "static-data-annotator"
41
42using namespace llvm;
43
44/// A module pass which iterates global variables in the module and annotates
45/// their section prefixes based on profile-driven analysis.
46class StaticDataAnnotatorLegacy : public ModulePass {
47public:
48 static char ID;
49
50 StaticDataAnnotatorLegacy() : ModulePass(ID) {}
51
52 void getAnalysisUsage(AnalysisUsage &AU) const override {
53 AU.addRequired<StaticDataProfileInfoWrapperPass>();
54 AU.addRequired<ProfileSummaryInfoWrapperPass>();
55 AU.setPreservesAll();
56 ModulePass::getAnalysisUsage(AU);
57 }
58
59 StringRef getPassName() const override { return "Static Data Annotator"; }
60
61 bool runOnModule(Module &M) override;
62};
63
64static bool annotateModule(Module &M, StaticDataProfileInfo *SDPI,
65 ProfileSummaryInfo *PSI) {
66 if (!PSI || !PSI->hasProfileSummary())
67 return false;
68
69 bool Changed = false;
70 for (auto &GV : M.globals()) {
71 if (!llvm::memprof::IsAnnotationOK(GV))
72 continue;
73
74 StringRef SectionPrefix = SDPI->getConstantSectionPrefix(C: &GV, PSI);
75 // setSectionPrefix returns true if the section prefix is updated.
76 Changed |= GV.setSectionPrefix(SectionPrefix);
77 }
78
79 return Changed;
80}
81
82bool StaticDataAnnotatorLegacy::runOnModule(Module &M) {
83 StaticDataProfileInfo *SDPI = &getAnalysis<StaticDataProfileInfoWrapperPass>()
84 .getStaticDataProfileInfo();
85 ProfileSummaryInfo *PSI =
86 &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
87 return annotateModule(M, SDPI, PSI);
88}
89
90char StaticDataAnnotatorLegacy::ID = 0;
91
92INITIALIZE_PASS(StaticDataAnnotatorLegacy, DEBUG_TYPE, "Static Data Annotator",
93 false, false)
94
95ModulePass *llvm::createStaticDataAnnotatorLegacyPass() {
96 return new StaticDataAnnotatorLegacy();
97}
98
99PreservedAnalyses StaticDataAnnoatorPass::run(Module &M,
100 ModuleAnalysisManager &MAM) {
101 StaticDataProfileInfo *SDPI = &MAM.getResult<StaticDataProfileInfoAnalysis>(IR&: M)
102 .getStaticDataProfileInfo();
103 ProfileSummaryInfo *PSI = &MAM.getResult<ProfileSummaryAnalysis>(IR&: M);
104 return annotateModule(M, SDPI, PSI)
105 ? PreservedAnalyses::none().preserveSet<CFGAnalyses>()
106 : PreservedAnalyses::all();
107}
108