1 //===- MachineLoopInfo.cpp - Natural Loop Calculator ----------------------===//
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
7 //===----------------------------------------------------------------------===//
9 // This file defines the MachineLoopInfo class that is used to identify natural
10 // loops and determine the loop depth of various nodes of the CFG. Note that
11 // the loops identified may actually be several natural loops that share the
12 // same header node... not just a single natural loop.
14 //===----------------------------------------------------------------------===//
16 #include "llvm/CodeGen/MachineLoopInfo.h"
17 #include "llvm/Analysis/LoopInfoImpl.h"
18 #include "llvm/CodeGen/MachineDominators.h"
19 #include "llvm/CodeGen/Passes.h"
20 #include "llvm/Config/llvm-config.h"
21 #include "llvm/InitializePasses.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/raw_ostream.h"
26 // Explicitly instantiate methods in LoopInfoImpl.h for MI-level Loops.
27 template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
28 template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
30 char MachineLoopInfo::ID = 0;
31 MachineLoopInfo::MachineLoopInfo() : MachineFunctionPass(ID) {
32 initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
34 INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",
35 "Machine Natural Loop Construction", true, true)
36 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
37 INITIALIZE_PASS_END(MachineLoopInfo, "machine-loops",
38 "Machine Natural Loop Construction", true, true)
40 char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
42 bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
43 calculate(getAnalysis<MachineDominatorTree>());
47 void MachineLoopInfo::calculate(MachineDominatorTree &MDT) {
49 LI.analyze(MDT.getBase());
52 void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
54 AU.addRequired<MachineDominatorTree>();
55 MachineFunctionPass::getAnalysisUsage(AU);
58 MachineBasicBlock *MachineLoop::getTopBlock() {
59 MachineBasicBlock *TopMBB = getHeader();
60 MachineFunction::iterator Begin = TopMBB->getParent()->begin();
61 if (TopMBB->getIterator() != Begin) {
62 MachineBasicBlock *PriorMBB = &*std::prev(TopMBB->getIterator());
63 while (contains(PriorMBB)) {
65 if (TopMBB->getIterator() == Begin)
67 PriorMBB = &*std::prev(TopMBB->getIterator());
73 MachineBasicBlock *MachineLoop::getBottomBlock() {
74 MachineBasicBlock *BotMBB = getHeader();
75 MachineFunction::iterator End = BotMBB->getParent()->end();
76 if (BotMBB->getIterator() != std::prev(End)) {
77 MachineBasicBlock *NextMBB = &*std::next(BotMBB->getIterator());
78 while (contains(NextMBB)) {
80 if (BotMBB == &*std::next(BotMBB->getIterator()))
82 NextMBB = &*std::next(BotMBB->getIterator());
88 MachineBasicBlock *MachineLoop::findLoopControlBlock() {
89 if (MachineBasicBlock *Latch = getLoopLatch()) {
90 if (isLoopExiting(Latch))
93 return getExitingBlock();
98 DebugLoc MachineLoop::getStartLoc() const {
99 // Try the pre-header first.
100 if (MachineBasicBlock *PHeadMBB = getLoopPreheader())
101 if (const BasicBlock *PHeadBB = PHeadMBB->getBasicBlock())
102 if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
105 // If we have no pre-header or there are no instructions with debug
106 // info in it, try the header.
107 if (MachineBasicBlock *HeadMBB = getHeader())
108 if (const BasicBlock *HeadBB = HeadMBB->getBasicBlock())
109 return HeadBB->getTerminator()->getDebugLoc();
115 MachineLoopInfo::findLoopPreheader(MachineLoop *L,
116 bool SpeculativePreheader) const {
117 if (MachineBasicBlock *PB = L->getLoopPreheader())
120 if (!SpeculativePreheader)
123 MachineBasicBlock *HB = L->getHeader(), *LB = L->getLoopLatch();
124 if (HB->pred_size() != 2 || HB->hasAddressTaken())
126 // Find the predecessor of the header that is not the latch block.
127 MachineBasicBlock *Preheader = nullptr;
128 for (MachineBasicBlock *P : HB->predecessors()) {
137 // Check if the preheader candidate is a successor of any other loop
138 // headers. We want to avoid having two loop setups in the same block.
139 for (MachineBasicBlock *S : Preheader->successors()) {
142 MachineLoop *T = getLoopFor(S);
143 if (T && T->getHeader() == S)
149 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
150 LLVM_DUMP_METHOD void MachineLoop::dump() const {