1 //===- MachineLoopInfo.cpp - Natural Loop Calculator ----------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the MachineLoopInfo class that is used to identify natural
11 // loops and determine the loop depth of various nodes of the CFG. Note that
12 // the loops identified may actually be several natural loops that share the
13 // same header node... not just a single natural loop.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/CodeGen/MachineLoopInfo.h"
18 #include "llvm/Analysis/LoopInfoImpl.h"
19 #include "llvm/CodeGen/MachineDominators.h"
20 #include "llvm/CodeGen/Passes.h"
21 #include "llvm/Support/Debug.h"
22 #include "llvm/Support/raw_ostream.h"
25 // Explicitly instantiate methods in LoopInfoImpl.h for MI-level Loops.
26 template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
27 template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
29 char MachineLoopInfo::ID = 0;
30 INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",
31 "Machine Natural Loop Construction", true, true)
32 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
33 INITIALIZE_PASS_END(MachineLoopInfo, "machine-loops",
34 "Machine Natural Loop Construction", true, true)
36 char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
38 bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
40 LI.analyze(getAnalysis<MachineDominatorTree>().getBase());
44 void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
46 AU.addRequired<MachineDominatorTree>();
47 MachineFunctionPass::getAnalysisUsage(AU);
50 MachineBasicBlock *MachineLoop::getTopBlock() {
51 MachineBasicBlock *TopMBB = getHeader();
52 MachineFunction::iterator Begin = TopMBB->getParent()->begin();
53 if (TopMBB->getIterator() != Begin) {
54 MachineBasicBlock *PriorMBB = &*std::prev(TopMBB->getIterator());
55 while (contains(PriorMBB)) {
57 if (TopMBB->getIterator() == Begin)
59 PriorMBB = &*std::prev(TopMBB->getIterator());
65 MachineBasicBlock *MachineLoop::getBottomBlock() {
66 MachineBasicBlock *BotMBB = getHeader();
67 MachineFunction::iterator End = BotMBB->getParent()->end();
68 if (BotMBB->getIterator() != std::prev(End)) {
69 MachineBasicBlock *NextMBB = &*std::next(BotMBB->getIterator());
70 while (contains(NextMBB)) {
72 if (BotMBB == &*std::next(BotMBB->getIterator()))
74 NextMBB = &*std::next(BotMBB->getIterator());
80 MachineBasicBlock *MachineLoop::findLoopControlBlock() {
81 if (MachineBasicBlock *Latch = getLoopLatch()) {
82 if (isLoopExiting(Latch))
85 return getExitingBlock();
90 DebugLoc MachineLoop::getStartLoc() const {
91 // Try the pre-header first.
92 if (MachineBasicBlock *PHeadMBB = getLoopPreheader())
93 if (const BasicBlock *PHeadBB = PHeadMBB->getBasicBlock())
94 if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
97 // If we have no pre-header or there are no instructions with debug
98 // info in it, try the header.
99 if (MachineBasicBlock *HeadMBB = getHeader())
100 if (const BasicBlock *HeadBB = HeadMBB->getBasicBlock())
101 return HeadBB->getTerminator()->getDebugLoc();
107 MachineLoopInfo::findLoopPreheader(MachineLoop *L,
108 bool SpeculativePreheader) const {
109 if (MachineBasicBlock *PB = L->getLoopPreheader())
112 if (!SpeculativePreheader)
115 MachineBasicBlock *HB = L->getHeader(), *LB = L->getLoopLatch();
116 if (HB->pred_size() != 2 || HB->hasAddressTaken())
118 // Find the predecessor of the header that is not the latch block.
119 MachineBasicBlock *Preheader = nullptr;
120 for (MachineBasicBlock *P : HB->predecessors()) {
129 // Check if the preheader candidate is a successor of any other loop
130 // headers. We want to avoid having two loop setups in the same block.
131 for (MachineBasicBlock *S : Preheader->successors()) {
134 MachineLoop *T = getLoopFor(S);
135 if (T && T->getHeader() == S)
141 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
142 LLVM_DUMP_METHOD void MachineLoop::dump() const {