1///===- LazyMachineBlockFrequencyInfo.cpp - Lazy Machine Block Frequency --===//
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/// This is an alternative analysis pass to MachineBlockFrequencyInfo. The
10/// difference is that with this pass the block frequencies are not computed
11/// when the analysis pass is executed but rather when the BFI result is
12/// explicitly requested by the analysis client.
13///
14///===---------------------------------------------------------------------===//
15
16#include "llvm/CodeGen/LazyMachineBlockFrequencyInfo.h"
17#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
18#include "llvm/InitializePasses.h"
19
20using namespace llvm;
21
22#define DEBUG_TYPE "lazy-machine-block-freq"
23
24INITIALIZE_PASS_BEGIN(LazyMachineBlockFrequencyInfoPass, DEBUG_TYPE,
25 "Lazy Machine Block Frequency Analysis", true, true)
26INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfoWrapperPass)
27INITIALIZE_PASS_DEPENDENCY(MachineLoopInfoWrapperPass)
28INITIALIZE_PASS_END(LazyMachineBlockFrequencyInfoPass, DEBUG_TYPE,
29 "Lazy Machine Block Frequency Analysis", true, true)
30
31char LazyMachineBlockFrequencyInfoPass::ID = 0;
32
33LazyMachineBlockFrequencyInfoPass::LazyMachineBlockFrequencyInfoPass()
34 : MachineFunctionPass(ID) {
35 initializeLazyMachineBlockFrequencyInfoPassPass(
36 Registry&: *PassRegistry::getPassRegistry());
37}
38
39void LazyMachineBlockFrequencyInfoPass::getAnalysisUsage(
40 AnalysisUsage &AU) const {
41 AU.addRequired<MachineBranchProbabilityInfoWrapperPass>();
42 AU.setPreservesAll();
43 MachineFunctionPass::getAnalysisUsage(AU);
44}
45
46void LazyMachineBlockFrequencyInfoPass::releaseMemory() {
47 OwnedMBFI.reset();
48 OwnedMLI.reset();
49 OwnedMDT.reset();
50}
51
52MachineBlockFrequencyInfo &
53LazyMachineBlockFrequencyInfoPass::calculateIfNotAvailable() const {
54 auto *MBFIWrapper =
55 getAnalysisIfAvailable<MachineBlockFrequencyInfoWrapperPass>();
56 if (MBFIWrapper) {
57 LLVM_DEBUG(dbgs() << "MachineBlockFrequencyInfo is available\n");
58 return MBFIWrapper->getMBFI();
59 }
60
61 auto &MBPI = getAnalysis<MachineBranchProbabilityInfoWrapperPass>().getMBPI();
62 auto *MLIWrapper = getAnalysisIfAvailable<MachineLoopInfoWrapperPass>();
63 auto *MLI = MLIWrapper ? &MLIWrapper->getLI() : nullptr;
64 auto *MDTWrapper = getAnalysisIfAvailable<MachineDominatorTreeWrapperPass>();
65 auto *MDT = MDTWrapper ? &MDTWrapper->getDomTree() : nullptr;
66 LLVM_DEBUG(dbgs() << "Building MachineBlockFrequencyInfo on the fly\n");
67 LLVM_DEBUG(if (MLI) dbgs() << "LoopInfo is available\n");
68
69 if (!MLI) {
70 LLVM_DEBUG(dbgs() << "Building LoopInfo on the fly\n");
71 // First create a dominator tree.
72 LLVM_DEBUG(if (MDT) dbgs() << "DominatorTree is available\n");
73
74 if (!MDT) {
75 LLVM_DEBUG(dbgs() << "Building DominatorTree on the fly\n");
76 OwnedMDT = std::make_unique<MachineDominatorTree>();
77 OwnedMDT->recalculate(Func&: *MF);
78 MDT = OwnedMDT.get();
79 }
80
81 // Generate LoopInfo from it.
82 OwnedMLI = std::make_unique<MachineLoopInfo>();
83 OwnedMLI->analyze(DomTree: *MDT);
84 MLI = OwnedMLI.get();
85 }
86
87 OwnedMBFI = std::make_unique<MachineBlockFrequencyInfo>();
88 OwnedMBFI->calculate(F: *MF, MBPI, MLI: *MLI);
89 return *OwnedMBFI;
90}
91
92bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction(
93 MachineFunction &F) {
94 MF = &F;
95 return false;
96}
97