1 //===- lib/CodeGen/MachineTraceMetrics.cpp ----------------------*- C++ -*-===//
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 #define DEBUG_TYPE "early-ifcvt"
11 #include "MachineTraceMetrics.h"
12 #include "llvm/CodeGen/MachineBasicBlock.h"
13 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
14 #include "llvm/CodeGen/MachineLoopInfo.h"
15 #include "llvm/CodeGen/MachineRegisterInfo.h"
16 #include "llvm/CodeGen/Passes.h"
17 #include "llvm/Target/TargetInstrInfo.h"
18 #include "llvm/Target/TargetRegisterInfo.h"
19 #include "llvm/Support/Debug.h"
20 #include "llvm/Support/raw_ostream.h"
21 #include "llvm/ADT/PostOrderIterator.h"
25 char MachineTraceMetrics::ID = 0;
26 char &llvm::MachineTraceMetricsID = MachineTraceMetrics::ID;
28 INITIALIZE_PASS_BEGIN(MachineTraceMetrics,
29 "machine-trace-metrics", "Machine Trace Metrics", false, true)
30 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
31 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
32 INITIALIZE_PASS_END(MachineTraceMetrics,
33 "machine-trace-metrics", "Machine Trace Metrics", false, true)
35 MachineTraceMetrics::MachineTraceMetrics()
36 : MachineFunctionPass(ID), TII(0), TRI(0), MRI(0), Loops(0) {
37 std::fill(Ensembles, array_endof(Ensembles), (Ensemble*)0);
40 void MachineTraceMetrics::getAnalysisUsage(AnalysisUsage &AU) const {
42 AU.addRequired<MachineBranchProbabilityInfo>();
43 AU.addRequired<MachineLoopInfo>();
44 MachineFunctionPass::getAnalysisUsage(AU);
47 bool MachineTraceMetrics::runOnMachineFunction(MachineFunction &Func) {
49 TII = MF->getTarget().getInstrInfo();
50 TRI = MF->getTarget().getRegisterInfo();
51 MRI = &MF->getRegInfo();
52 Loops = &getAnalysis<MachineLoopInfo>();
53 BlockInfo.resize(MF->getNumBlockIDs());
57 void MachineTraceMetrics::releaseMemory() {
59 for (unsigned i = 0; i != TS_NumStrategies; ++i) {
65 //===----------------------------------------------------------------------===//
66 // Fixed block information
67 //===----------------------------------------------------------------------===//
69 // The number of instructions in a basic block and the CPU resources used by
70 // those instructions don't depend on any given trace strategy.
72 /// Compute the resource usage in basic block MBB.
73 const MachineTraceMetrics::FixedBlockInfo*
74 MachineTraceMetrics::getResources(const MachineBasicBlock *MBB) {
75 assert(MBB && "No basic block");
76 FixedBlockInfo *FBI = &BlockInfo[MBB->getNumber()];
77 if (FBI->hasResources())
80 // Compute resource usage in the block.
81 // FIXME: Compute per-functional unit counts.
82 FBI->HasCalls = false;
83 unsigned InstrCount = 0;
84 for (MachineBasicBlock::const_iterator I = MBB->begin(), E = MBB->end();
86 const MachineInstr *MI = I;
87 if (MI->isTransient())
93 FBI->InstrCount = InstrCount;
97 //===----------------------------------------------------------------------===//
98 // Ensemble utility functions
99 //===----------------------------------------------------------------------===//
101 MachineTraceMetrics::Ensemble::Ensemble(MachineTraceMetrics *ct)
103 BlockInfo.resize(CT.BlockInfo.size());
106 // Virtual destructor serves as an anchor.
107 MachineTraceMetrics::Ensemble::~Ensemble() {}
110 MachineTraceMetrics::Ensemble::getLoopFor(const MachineBasicBlock *MBB) const {
111 return CT.Loops->getLoopFor(MBB);
114 // Update resource-related information in the TraceBlockInfo for MBB.
115 // Only update resources related to the trace above MBB.
116 void MachineTraceMetrics::Ensemble::
117 computeDepthResources(const MachineBasicBlock *MBB) {
118 TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()];
120 // Compute resources from trace above. The top block is simple.
123 TBI->Head = MBB->getNumber();
127 // Compute from the block above. A post-order traversal ensures the
128 // predecessor is always computed first.
129 TraceBlockInfo *PredTBI = &BlockInfo[TBI->Pred->getNumber()];
130 assert(PredTBI->hasValidDepth() && "Trace above has not been computed yet");
131 const FixedBlockInfo *PredFBI = CT.getResources(TBI->Pred);
132 TBI->InstrDepth = PredTBI->InstrDepth + PredFBI->InstrCount;
133 TBI->Head = PredTBI->Head;
136 // Update resource-related information in the TraceBlockInfo for MBB.
137 // Only update resources related to the trace below MBB.
138 void MachineTraceMetrics::Ensemble::
139 computeHeightResources(const MachineBasicBlock *MBB) {
140 TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()];
142 // Compute resources for the current block.
143 TBI->InstrHeight = CT.getResources(MBB)->InstrCount;
145 // The trace tail is done.
147 TBI->Tail = MBB->getNumber();
151 // Compute from the block below. A post-order traversal ensures the
152 // predecessor is always computed first.
153 TraceBlockInfo *SuccTBI = &BlockInfo[TBI->Succ->getNumber()];
154 assert(SuccTBI->hasValidHeight() && "Trace below has not been computed yet");
155 TBI->InstrHeight += SuccTBI->InstrHeight;
156 TBI->Tail = SuccTBI->Tail;
159 // Check if depth resources for MBB are valid and return the TBI.
160 // Return NULL if the resources have been invalidated.
161 const MachineTraceMetrics::TraceBlockInfo*
162 MachineTraceMetrics::Ensemble::
163 getDepthResources(const MachineBasicBlock *MBB) const {
164 const TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()];
165 return TBI->hasValidDepth() ? TBI : 0;
168 // Check if height resources for MBB are valid and return the TBI.
169 // Return NULL if the resources have been invalidated.
170 const MachineTraceMetrics::TraceBlockInfo*
171 MachineTraceMetrics::Ensemble::
172 getHeightResources(const MachineBasicBlock *MBB) const {
173 const TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()];
174 return TBI->hasValidHeight() ? TBI : 0;
177 //===----------------------------------------------------------------------===//
178 // Trace Selection Strategies
179 //===----------------------------------------------------------------------===//
181 // A trace selection strategy is implemented as a sub-class of Ensemble. The
182 // trace through a block B is computed by two DFS traversals of the CFG
183 // starting from B. One upwards, and one downwards. During the upwards DFS,
184 // pickTracePred() is called on the post-ordered blocks. During the downwards
185 // DFS, pickTraceSucc() is called in a post-order.
188 // We never allow traces that leave loops, but we do allow traces to enter
189 // nested loops. We also never allow traces to contain back-edges.
191 // This means that a loop header can never appear above the center block of a
192 // trace, except as the trace head. Below the center block, loop exiting edges
195 // Return true if an edge from the From loop to the To loop is leaving a loop.
196 // Either of To and From can be null.
197 static bool isExitingLoop(const MachineLoop *From, const MachineLoop *To) {
198 return From && !From->contains(To);
201 // MinInstrCountEnsemble - Pick the trace that executes the least number of
204 class MinInstrCountEnsemble : public MachineTraceMetrics::Ensemble {
205 const char *getName() const { return "MinInstr"; }
206 const MachineBasicBlock *pickTracePred(const MachineBasicBlock*);
207 const MachineBasicBlock *pickTraceSucc(const MachineBasicBlock*);
210 MinInstrCountEnsemble(MachineTraceMetrics *ct)
211 : MachineTraceMetrics::Ensemble(ct) {}
215 // Select the preferred predecessor for MBB.
216 const MachineBasicBlock*
217 MinInstrCountEnsemble::pickTracePred(const MachineBasicBlock *MBB) {
218 if (MBB->pred_empty())
220 const MachineLoop *CurLoop = getLoopFor(MBB);
221 // Don't leave loops, and never follow back-edges.
222 if (CurLoop && MBB == CurLoop->getHeader())
224 unsigned CurCount = CT.getResources(MBB)->InstrCount;
225 const MachineBasicBlock *Best = 0;
226 unsigned BestDepth = 0;
227 for (MachineBasicBlock::const_pred_iterator
228 I = MBB->pred_begin(), E = MBB->pred_end(); I != E; ++I) {
229 const MachineBasicBlock *Pred = *I;
230 const MachineTraceMetrics::TraceBlockInfo *PredTBI =
231 getDepthResources(Pred);
232 assert(PredTBI && "Predecessor must be visited first");
233 // Pick the predecessor that would give this block the smallest InstrDepth.
234 unsigned Depth = PredTBI->InstrDepth + CurCount;
235 if (!Best || Depth < BestDepth)
236 Best = Pred, BestDepth = Depth;
241 // Select the preferred successor for MBB.
242 const MachineBasicBlock*
243 MinInstrCountEnsemble::pickTraceSucc(const MachineBasicBlock *MBB) {
244 if (MBB->pred_empty())
246 const MachineLoop *CurLoop = getLoopFor(MBB);
247 const MachineBasicBlock *Best = 0;
248 unsigned BestHeight = 0;
249 for (MachineBasicBlock::const_succ_iterator
250 I = MBB->succ_begin(), E = MBB->succ_end(); I != E; ++I) {
251 const MachineBasicBlock *Succ = *I;
252 // Don't consider back-edges.
253 if (CurLoop && Succ == CurLoop->getHeader())
255 // Don't consider successors exiting CurLoop.
256 if (isExitingLoop(CurLoop, getLoopFor(Succ)))
258 const MachineTraceMetrics::TraceBlockInfo *SuccTBI =
259 getHeightResources(Succ);
260 assert(SuccTBI && "Successor must be visited first");
261 // Pick the successor that would give this block the smallest InstrHeight.
262 unsigned Height = SuccTBI->InstrHeight;
263 if (!Best || Height < BestHeight)
264 Best = Succ, BestHeight = Height;
269 // Get an Ensemble sub-class for the requested trace strategy.
270 MachineTraceMetrics::Ensemble *
271 MachineTraceMetrics::getEnsemble(MachineTraceMetrics::Strategy strategy) {
272 assert(strategy < TS_NumStrategies && "Invalid trace strategy enum");
273 Ensemble *&E = Ensembles[strategy];
277 // Allocate new Ensemble on demand.
279 case TS_MinInstrCount: return (E = new MinInstrCountEnsemble(this));
280 default: llvm_unreachable("Invalid trace strategy enum");
284 void MachineTraceMetrics::invalidate(const MachineBasicBlock *MBB) {
285 DEBUG(dbgs() << "Invalidate traces through BB#" << MBB->getNumber() << '\n');
286 BlockInfo[MBB->getNumber()].invalidate();
287 for (unsigned i = 0; i != TS_NumStrategies; ++i)
289 Ensembles[i]->invalidate(MBB);
292 void MachineTraceMetrics::verifyAnalysis() const {
294 assert(BlockInfo.size() == MF->getNumBlockIDs() && "Outdated BlockInfo size");
295 for (unsigned i = 0; i != TS_NumStrategies; ++i)
297 Ensembles[i]->verify();
301 //===----------------------------------------------------------------------===//
303 //===----------------------------------------------------------------------===//
305 // Traces are built by two CFG traversals. To avoid recomputing too much, use a
306 // set abstraction that confines the search to the current loop, and doesn't
311 MutableArrayRef<MachineTraceMetrics::TraceBlockInfo> Blocks;
312 const MachineLoopInfo *Loops;
314 LoopBounds(MutableArrayRef<MachineTraceMetrics::TraceBlockInfo> blocks,
315 const MachineLoopInfo *loops)
316 : Blocks(blocks), Loops(loops), Downward(false) {}
320 // Specialize po_iterator_storage in order to prune the post-order traversal so
321 // it is limited to the current loop and doesn't traverse the loop back edges.
324 class po_iterator_storage<LoopBounds, true> {
327 po_iterator_storage(LoopBounds &lb) : LB(lb) {}
328 void finishPostorder(const MachineBasicBlock*) {}
330 bool insertEdge(const MachineBasicBlock *From, const MachineBasicBlock *To) {
331 // Skip already visited To blocks.
332 MachineTraceMetrics::TraceBlockInfo &TBI = LB.Blocks[To->getNumber()];
333 if (LB.Downward ? TBI.hasValidHeight() : TBI.hasValidDepth())
335 // From is null once when To is the trace center block.
338 const MachineLoop *FromLoop = LB.Loops->getLoopFor(From);
341 // Don't follow backedges, don't leave FromLoop when going upwards.
342 if ((LB.Downward ? To : From) == FromLoop->getHeader())
344 // Don't leave FromLoop.
345 if (isExitingLoop(FromLoop, LB.Loops->getLoopFor(To)))
347 // This is a new block. The PO traversal will compute height/depth
348 // resources, causing us to reject new edges to To. This only works because
349 // we reject back-edges, so the CFG is cycle-free.
355 /// Compute the trace through MBB.
356 void MachineTraceMetrics::Ensemble::computeTrace(const MachineBasicBlock *MBB) {
357 DEBUG(dbgs() << "Computing " << getName() << " trace through BB#"
358 << MBB->getNumber() << '\n');
359 // Set up loop bounds for the backwards post-order traversal.
360 LoopBounds Bounds(BlockInfo, CT.Loops);
362 // Run an upwards post-order search for the trace start.
363 Bounds.Downward = false;
364 typedef ipo_ext_iterator<const MachineBasicBlock*, LoopBounds> UpwardPO;
365 for (UpwardPO I = ipo_ext_begin(MBB, Bounds), E = ipo_ext_end(MBB, Bounds);
367 DEBUG(dbgs() << " pred for BB#" << I->getNumber() << ": ");
368 TraceBlockInfo &TBI = BlockInfo[I->getNumber()];
369 // All the predecessors have been visited, pick the preferred one.
370 TBI.Pred = pickTracePred(*I);
373 dbgs() << "BB#" << TBI.Pred->getNumber() << '\n';
377 // The trace leading to I is now known, compute the depth resources.
378 computeDepthResources(*I);
381 // Run a downwards post-order search for the trace end.
382 Bounds.Downward = true;
383 typedef po_ext_iterator<const MachineBasicBlock*, LoopBounds> DownwardPO;
384 for (DownwardPO I = po_ext_begin(MBB, Bounds), E = po_ext_end(MBB, Bounds);
386 DEBUG(dbgs() << " succ for BB#" << I->getNumber() << ": ");
387 TraceBlockInfo &TBI = BlockInfo[I->getNumber()];
388 // All the successors have been visited, pick the preferred one.
389 TBI.Succ = pickTraceSucc(*I);
392 dbgs() << "BB#" << TBI.Succ->getNumber() << '\n';
396 // The trace leaving I is now known, compute the height resources.
397 computeHeightResources(*I);
401 /// Invalidate traces through BadMBB.
403 MachineTraceMetrics::Ensemble::invalidate(const MachineBasicBlock *BadMBB) {
404 SmallVector<const MachineBasicBlock*, 16> WorkList;
405 TraceBlockInfo &BadTBI = BlockInfo[BadMBB->getNumber()];
407 // Invalidate height resources of blocks above MBB.
408 if (BadTBI.hasValidHeight()) {
409 BadTBI.invalidateHeight();
410 WorkList.push_back(BadMBB);
412 const MachineBasicBlock *MBB = WorkList.pop_back_val();
413 DEBUG(dbgs() << "Invalidate BB#" << MBB->getNumber() << ' ' << getName()
415 // Find any MBB predecessors that have MBB as their preferred successor.
416 // They are the only ones that need to be invalidated.
417 for (MachineBasicBlock::const_pred_iterator
418 I = MBB->pred_begin(), E = MBB->pred_end(); I != E; ++I) {
419 TraceBlockInfo &TBI = BlockInfo[(*I)->getNumber()];
420 if (!TBI.hasValidHeight())
422 if (TBI.Succ == MBB) {
423 TBI.invalidateHeight();
424 WorkList.push_back(*I);
427 // Verify that TBI.Succ is actually a *I successor.
428 assert((!TBI.Succ || (*I)->isSuccessor(TBI.Succ)) && "CFG changed");
430 } while (!WorkList.empty());
433 // Invalidate depth resources of blocks below MBB.
434 if (BadTBI.hasValidDepth()) {
435 BadTBI.invalidateDepth();
436 WorkList.push_back(BadMBB);
438 const MachineBasicBlock *MBB = WorkList.pop_back_val();
439 DEBUG(dbgs() << "Invalidate BB#" << MBB->getNumber() << ' ' << getName()
441 // Find any MBB successors that have MBB as their preferred predecessor.
442 // They are the only ones that need to be invalidated.
443 for (MachineBasicBlock::const_succ_iterator
444 I = MBB->succ_begin(), E = MBB->succ_end(); I != E; ++I) {
445 TraceBlockInfo &TBI = BlockInfo[(*I)->getNumber()];
446 if (!TBI.hasValidDepth())
448 if (TBI.Pred == MBB) {
449 TBI.invalidateDepth();
450 WorkList.push_back(*I);
453 // Verify that TBI.Pred is actually a *I predecessor.
454 assert((!TBI.Pred || (*I)->isPredecessor(TBI.Pred)) && "CFG changed");
456 } while (!WorkList.empty());
460 void MachineTraceMetrics::Ensemble::verify() const {
462 assert(BlockInfo.size() == CT.MF->getNumBlockIDs() &&
463 "Outdated BlockInfo size");
464 for (unsigned Num = 0, e = BlockInfo.size(); Num != e; ++Num) {
465 const TraceBlockInfo &TBI = BlockInfo[Num];
466 if (TBI.hasValidDepth() && TBI.Pred) {
467 const MachineBasicBlock *MBB = CT.MF->getBlockNumbered(Num);
468 assert(MBB->isPredecessor(TBI.Pred) && "CFG doesn't match trace");
469 assert(BlockInfo[TBI.Pred->getNumber()].hasValidDepth() &&
470 "Trace is broken, depth should have been invalidated.");
471 const MachineLoop *Loop = getLoopFor(MBB);
472 assert(!(Loop && MBB == Loop->getHeader()) && "Trace contains backedge");
474 if (TBI.hasValidHeight() && TBI.Succ) {
475 const MachineBasicBlock *MBB = CT.MF->getBlockNumbered(Num);
476 assert(MBB->isSuccessor(TBI.Succ) && "CFG doesn't match trace");
477 assert(BlockInfo[TBI.Succ->getNumber()].hasValidHeight() &&
478 "Trace is broken, height should have been invalidated.");
479 const MachineLoop *Loop = getLoopFor(MBB);
480 const MachineLoop *SuccLoop = getLoopFor(TBI.Succ);
481 assert(!(Loop && Loop == SuccLoop && TBI.Succ == Loop->getHeader()) &&
482 "Trace contains backedge");
488 MachineTraceMetrics::Trace
489 MachineTraceMetrics::Ensemble::getTrace(const MachineBasicBlock *MBB) {
490 // FIXME: Check cache tags, recompute as needed.
492 return Trace(*this, BlockInfo[MBB->getNumber()]);
495 void MachineTraceMetrics::Ensemble::print(raw_ostream &OS) const {
496 OS << getName() << " ensemble:\n";
497 for (unsigned i = 0, e = BlockInfo.size(); i != e; ++i) {
498 OS << " BB#" << i << '\t';
499 BlockInfo[i].print(OS);
504 void MachineTraceMetrics::TraceBlockInfo::print(raw_ostream &OS) const {
505 if (hasValidDepth()) {
506 OS << "depth=" << InstrDepth;
508 OS << " pred=BB#" << Pred->getNumber();
511 OS << " head=BB#" << Head;
513 OS << "depth invalid";
515 if (hasValidHeight()) {
516 OS << "height=" << InstrHeight;
518 OS << " succ=BB#" << Succ->getNumber();
521 OS << " tail=BB#" << Tail;
523 OS << "height invalid";
526 void MachineTraceMetrics::Trace::print(raw_ostream &OS) const {
527 unsigned MBBNum = &TBI - &TE.BlockInfo[0];
529 OS << TE.getName() << " trace BB#" << TBI.Head << " --> BB#" << MBBNum
530 << " --> BB#" << TBI.Tail << ':';
531 if (TBI.hasValidHeight() && TBI.hasValidDepth())
532 OS << ' ' << getInstrCount() << " instrs.";
534 const MachineTraceMetrics::TraceBlockInfo *Block = &TBI;
535 OS << "\nBB#" << MBBNum;
536 while (Block->hasValidDepth() && Block->Pred) {
537 unsigned Num = Block->Pred->getNumber();
538 OS << " <- BB#" << Num;
539 Block = &TE.BlockInfo[Num];
544 while (Block->hasValidHeight() && Block->Succ) {
545 unsigned Num = Block->Succ->getNumber();
546 OS << " -> BB#" << Num;
547 Block = &TE.BlockInfo[Num];