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
36void LazyMachineBlockFrequencyInfoPass::getAnalysisUsage(
37 AnalysisUsage &AU) const {
38 AU.addRequired<MachineBranchProbabilityInfoWrapperPass>();
39 AU.setPreservesAll();
40 MachineFunctionPass::getAnalysisUsage(AU);
41}
42
43void LazyMachineBlockFrequencyInfoPass::releaseMemory() {
44 OwnedMBFI.reset();
45 OwnedMLI.reset();
46 OwnedMDT.reset();
47}
48
49MachineBlockFrequencyInfo &
50LazyMachineBlockFrequencyInfoPass::calculateIfNotAvailable() const {
51 auto *MBFIWrapper =
52 getAnalysisIfAvailable<MachineBlockFrequencyInfoWrapperPass>();
53 if (MBFIWrapper) {
54 LLVM_DEBUG(dbgs() << "MachineBlockFrequencyInfo is available\n");
55 return MBFIWrapper->getMBFI();
56 }
57
58 auto &MBPI = getAnalysis<MachineBranchProbabilityInfoWrapperPass>().getMBPI();
59 auto *MLIWrapper = getAnalysisIfAvailable<MachineLoopInfoWrapperPass>();
60 auto *MLI = MLIWrapper ? &MLIWrapper->getLI() : nullptr;
61 auto *MDTWrapper = getAnalysisIfAvailable<MachineDominatorTreeWrapperPass>();
62 auto *MDT = MDTWrapper ? &MDTWrapper->getDomTree() : nullptr;
63 LLVM_DEBUG(dbgs() << "Building MachineBlockFrequencyInfo on the fly\n");
64 LLVM_DEBUG(if (MLI) dbgs() << "LoopInfo is available\n");
65
66 if (!MLI) {
67 LLVM_DEBUG(dbgs() << "Building LoopInfo on the fly\n");
68 // First create a dominator tree.
69 LLVM_DEBUG(if (MDT) dbgs() << "DominatorTree is available\n");
70
71 if (!MDT) {
72 LLVM_DEBUG(dbgs() << "Building DominatorTree on the fly\n");
73 OwnedMDT = std::make_unique<MachineDominatorTree>();
74 OwnedMDT->recalculate(Func&: *MF);
75 MDT = OwnedMDT.get();
76 }
77
78 // Generate LoopInfo from it.
79 OwnedMLI = std::make_unique<MachineLoopInfo>();
80 OwnedMLI->analyze(DomTree: *MDT);
81 MLI = OwnedMLI.get();
82 }
83
84 OwnedMBFI = std::make_unique<MachineBlockFrequencyInfo>();
85 OwnedMBFI->calculate(F: *MF, MBPI, MLI: *MLI);
86 return *OwnedMBFI;
87}
88
89bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction(
90 MachineFunction &F) {
91 MF = &F;
92 return false;
93}
94