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/Analysis/ProfileSummaryInfo.h"
31#include "llvm/Analysis/StaticDataProfileInfo.h"
32#include "llvm/CodeGen/Passes.h"
33#include "llvm/IR/Analysis.h"
34#include "llvm/IR/Module.h"
35#include "llvm/IR/PassManager.h"
36#include "llvm/InitializePasses.h"
37#include "llvm/Pass.h"
38
39#define DEBUG_TYPE "static-data-annotator"
40
41using namespace llvm;
42
43/// A module pass which iterates global variables in the module and annotates
44/// their section prefixes based on profile-driven analysis.
45class StaticDataAnnotator : public ModulePass {
46public:
47 static char ID;
48
49 StaticDataProfileInfo *SDPI = nullptr;
50 const ProfileSummaryInfo *PSI = nullptr;
51
52 StaticDataAnnotator() : ModulePass(ID) {}
53
54 void getAnalysisUsage(AnalysisUsage &AU) const override {
55 AU.addRequired<StaticDataProfileInfoWrapperPass>();
56 AU.addRequired<ProfileSummaryInfoWrapperPass>();
57 AU.setPreservesAll();
58 ModulePass::getAnalysisUsage(AU);
59 }
60
61 StringRef getPassName() const override { return "Static Data Annotator"; }
62
63 bool runOnModule(Module &M) override;
64};
65
66bool StaticDataAnnotator::runOnModule(Module &M) {
67 SDPI = &getAnalysis<StaticDataProfileInfoWrapperPass>()
68 .getStaticDataProfileInfo();
69 PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
70
71 if (!PSI->hasProfileSummary())
72 return false;
73
74 bool Changed = false;
75 for (auto &GV : M.globals()) {
76 if (!llvm::memprof::IsAnnotationOK(GV))
77 continue;
78
79 StringRef SectionPrefix = SDPI->getConstantSectionPrefix(C: &GV, PSI);
80 // setSectionPrefix returns true if the section prefix is updated.
81 Changed |= GV.setSectionPrefix(SectionPrefix);
82 }
83
84 return Changed;
85}
86
87char StaticDataAnnotator::ID = 0;
88
89INITIALIZE_PASS(StaticDataAnnotator, DEBUG_TYPE, "Static Data Annotator", false,
90 false)
91
92ModulePass *llvm::createStaticDataAnnotatorPass() {
93 return new StaticDataAnnotator();
94}
95