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 // MinInstrCountEnsemble - Pick the trace that executes the least number of
191 class MinInstrCountEnsemble : public MachineTraceMetrics::Ensemble {
192 const char *getName() const { return "MinInstr"; }
193 const MachineBasicBlock *pickTracePred(const MachineBasicBlock*);
194 const MachineBasicBlock *pickTraceSucc(const MachineBasicBlock*);
197 MinInstrCountEnsemble(MachineTraceMetrics *ct)
198 : MachineTraceMetrics::Ensemble(ct) {}
202 // Select the preferred predecessor for MBB.
203 const MachineBasicBlock*
204 MinInstrCountEnsemble::pickTracePred(const MachineBasicBlock *MBB) {
205 if (MBB->pred_empty())
207 const MachineLoop *CurLoop = getLoopFor(MBB);
208 // Don't leave loops, and never follow back-edges.
209 if (CurLoop && MBB == CurLoop->getHeader())
211 unsigned CurCount = CT.getResources(MBB)->InstrCount;
212 const MachineBasicBlock *Best = 0;
213 unsigned BestDepth = 0;
214 for (MachineBasicBlock::const_pred_iterator
215 I = MBB->pred_begin(), E = MBB->pred_end(); I != E; ++I) {
216 const MachineBasicBlock *Pred = *I;
217 const MachineTraceMetrics::TraceBlockInfo *PredTBI =
218 getDepthResources(Pred);
219 // Ignore invalidated predecessors. This never happens on the first scan,
220 // but if we rejected this predecessor earlier, it won't be revalidated.
223 // Don't consider predecessors in other loops.
224 if (getLoopFor(Pred) != CurLoop)
226 // Pick the predecessor that would give this block the smallest InstrDepth.
227 unsigned Depth = PredTBI->InstrDepth + CurCount;
228 if (!Best || Depth < BestDepth)
229 Best = Pred, BestDepth = Depth;
234 // Select the preferred successor for MBB.
235 const MachineBasicBlock*
236 MinInstrCountEnsemble::pickTraceSucc(const MachineBasicBlock *MBB) {
237 if (MBB->pred_empty())
239 const MachineLoop *CurLoop = getLoopFor(MBB);
240 const MachineBasicBlock *Best = 0;
241 unsigned BestHeight = 0;
242 for (MachineBasicBlock::const_succ_iterator
243 I = MBB->succ_begin(), E = MBB->succ_end(); I != E; ++I) {
244 const MachineBasicBlock *Succ = *I;
245 const MachineTraceMetrics::TraceBlockInfo *SuccTBI =
246 getHeightResources(Succ);
247 // Ignore invalidated successors.
250 // Don't consider back-edges.
251 if (CurLoop && Succ == CurLoop->getHeader())
253 // Don't consider successors in other loops.
254 if (getLoopFor(Succ) != CurLoop)
256 // Pick the successor that would give this block the smallest InstrHeight.
257 unsigned Height = SuccTBI->InstrHeight;
258 if (!Best || Height < BestHeight)
259 Best = Succ, BestHeight = Height;
264 // Get an Ensemble sub-class for the requested trace strategy.
265 MachineTraceMetrics::Ensemble *
266 MachineTraceMetrics::getEnsemble(MachineTraceMetrics::Strategy strategy) {
267 assert(strategy < TS_NumStrategies && "Invalid trace strategy enum");
268 Ensemble *&E = Ensembles[strategy];
272 // Allocate new Ensemble on demand.
274 case TS_MinInstrCount: return (E = new MinInstrCountEnsemble(this));
275 default: llvm_unreachable("Invalid trace strategy enum");
279 void MachineTraceMetrics::invalidate(const MachineBasicBlock *MBB) {
280 DEBUG(dbgs() << "Invalidate traces through BB#" << MBB->getNumber() << '\n');
281 BlockInfo[MBB->getNumber()].invalidate();
282 for (unsigned i = 0; i != TS_NumStrategies; ++i)
284 Ensembles[i]->invalidate(MBB);
287 void MachineTraceMetrics::verifyAnalysis() const {
289 assert(BlockInfo.size() == MF->getNumBlockIDs() && "Outdated BlockInfo size");
290 for (unsigned i = 0; i != TS_NumStrategies; ++i)
292 Ensembles[i]->verify();
296 //===----------------------------------------------------------------------===//
298 //===----------------------------------------------------------------------===//
300 // Traces are built by two CFG traversals. To avoid recomputing too much, use a
301 // set abstraction that confines the search to the current loop, and doesn't
306 MutableArrayRef<MachineTraceMetrics::TraceBlockInfo> Blocks;
307 const MachineLoopInfo *Loops;
308 const MachineLoop *CurLoop;
310 LoopBounds(MutableArrayRef<MachineTraceMetrics::TraceBlockInfo> blocks,
311 const MachineLoopInfo *loops, const MachineLoop *curloop)
312 : Blocks(blocks), Loops(loops), CurLoop(curloop), Downward(false) {}
316 // Specialize po_iterator_storage in order to prune the post-order traversal so
317 // it is limited to the current loop and doesn't traverse the loop back edges.
320 class po_iterator_storage<LoopBounds, true> {
323 po_iterator_storage(LoopBounds &lb) : LB(lb) {}
324 void finishPostorder(const MachineBasicBlock*) {}
326 bool insertEdge(const MachineBasicBlock *From, const MachineBasicBlock *To) {
327 // Skip already visited To blocks.
328 MachineTraceMetrics::TraceBlockInfo &TBI = LB.Blocks[To->getNumber()];
329 if (LB.Downward ? TBI.hasValidHeight() : TBI.hasValidDepth())
331 // Don't follow CurLoop backedges.
332 if (LB.CurLoop && (LB.Downward ? To : From) == LB.CurLoop->getHeader())
334 // Don't leave CurLoop.
335 if (LB.Loops->getLoopFor(To) != LB.CurLoop)
337 // This is a new block. The PO traversal will compute height/depth
338 // resources, causing us to reject new edges to To. This only works because
339 // we reject back-edges, so the CFG is cycle-free.
345 /// Compute the trace through MBB.
346 void MachineTraceMetrics::Ensemble::computeTrace(const MachineBasicBlock *MBB) {
347 DEBUG(dbgs() << "Computing " << getName() << " trace through BB#"
348 << MBB->getNumber() << '\n');
349 // Set up loop bounds for the backwards post-order traversal.
350 LoopBounds Bounds(BlockInfo, CT.Loops, getLoopFor(MBB));
352 // Run an upwards post-order search for the trace start.
353 Bounds.Downward = false;
354 typedef ipo_ext_iterator<const MachineBasicBlock*, LoopBounds> UpwardPO;
355 for (UpwardPO I = ipo_ext_begin(MBB, Bounds), E = ipo_ext_end(MBB, Bounds);
357 DEBUG(dbgs() << " pred for BB#" << I->getNumber() << ": ");
358 TraceBlockInfo &TBI = BlockInfo[I->getNumber()];
359 // All the predecessors have been visited, pick the preferred one.
360 TBI.Pred = pickTracePred(*I);
363 dbgs() << "BB#" << TBI.Pred->getNumber() << '\n';
367 // The trace leading to I is now known, compute the depth resources.
368 computeDepthResources(*I);
371 // Run a downwards post-order search for the trace end.
372 Bounds.Downward = true;
373 typedef po_ext_iterator<const MachineBasicBlock*, LoopBounds> DownwardPO;
374 for (DownwardPO I = po_ext_begin(MBB, Bounds), E = po_ext_end(MBB, Bounds);
376 DEBUG(dbgs() << " succ for BB#" << I->getNumber() << ": ");
377 TraceBlockInfo &TBI = BlockInfo[I->getNumber()];
378 // All the successors have been visited, pick the preferred one.
379 TBI.Succ = pickTraceSucc(*I);
382 dbgs() << "BB#" << TBI.Succ->getNumber() << '\n';
386 // The trace leaving I is now known, compute the height resources.
387 computeHeightResources(*I);
391 /// Invalidate traces through BadMBB.
393 MachineTraceMetrics::Ensemble::invalidate(const MachineBasicBlock *BadMBB) {
394 SmallVector<const MachineBasicBlock*, 16> WorkList;
395 TraceBlockInfo &BadTBI = BlockInfo[BadMBB->getNumber()];
397 // Invalidate height resources of blocks above MBB.
398 if (BadTBI.hasValidHeight()) {
399 BadTBI.invalidateHeight();
400 WorkList.push_back(BadMBB);
402 const MachineBasicBlock *MBB = WorkList.pop_back_val();
403 DEBUG(dbgs() << "Invalidate BB#" << MBB->getNumber() << ' ' << getName()
405 // Find any MBB predecessors that have MBB as their preferred successor.
406 // They are the only ones that need to be invalidated.
407 for (MachineBasicBlock::const_pred_iterator
408 I = MBB->pred_begin(), E = MBB->pred_end(); I != E; ++I) {
409 TraceBlockInfo &TBI = BlockInfo[(*I)->getNumber()];
410 if (!TBI.hasValidHeight())
412 if (TBI.Succ == MBB) {
413 TBI.invalidateHeight();
414 WorkList.push_back(*I);
417 // Verify that TBI.Succ is actually a *I successor.
418 assert((!TBI.Succ || (*I)->isSuccessor(TBI.Succ)) && "CFG changed");
420 } while (!WorkList.empty());
423 // Invalidate depth resources of blocks below MBB.
424 if (BadTBI.hasValidDepth()) {
425 BadTBI.invalidateDepth();
426 WorkList.push_back(BadMBB);
428 const MachineBasicBlock *MBB = WorkList.pop_back_val();
429 DEBUG(dbgs() << "Invalidate BB#" << MBB->getNumber() << ' ' << getName()
431 // Find any MBB successors that have MBB as their preferred predecessor.
432 // They are the only ones that need to be invalidated.
433 for (MachineBasicBlock::const_succ_iterator
434 I = MBB->succ_begin(), E = MBB->succ_end(); I != E; ++I) {
435 TraceBlockInfo &TBI = BlockInfo[(*I)->getNumber()];
436 if (!TBI.hasValidDepth())
438 if (TBI.Pred == MBB) {
439 TBI.invalidateDepth();
440 WorkList.push_back(*I);
443 // Verify that TBI.Pred is actually a *I predecessor.
444 assert((!TBI.Pred || (*I)->isPredecessor(TBI.Pred)) && "CFG changed");
446 } while (!WorkList.empty());
450 void MachineTraceMetrics::Ensemble::verify() const {
452 assert(BlockInfo.size() == CT.MF->getNumBlockIDs() &&
453 "Outdated BlockInfo size");
454 for (unsigned Num = 0, e = BlockInfo.size(); Num != e; ++Num) {
455 const TraceBlockInfo &TBI = BlockInfo[Num];
456 if (TBI.hasValidDepth() && TBI.Pred) {
457 const MachineBasicBlock *MBB = CT.MF->getBlockNumbered(Num);
458 assert(MBB->isPredecessor(TBI.Pred) && "CFG doesn't match trace");
459 assert(BlockInfo[TBI.Pred->getNumber()].hasValidDepth() &&
460 "Trace is broken, depth should have been invalidated.");
461 const MachineLoop *Loop = getLoopFor(MBB);
462 assert(!(Loop && MBB == Loop->getHeader()) && "Trace contains backedge");
464 if (TBI.hasValidHeight() && TBI.Succ) {
465 const MachineBasicBlock *MBB = CT.MF->getBlockNumbered(Num);
466 assert(MBB->isSuccessor(TBI.Succ) && "CFG doesn't match trace");
467 assert(BlockInfo[TBI.Succ->getNumber()].hasValidHeight() &&
468 "Trace is broken, height should have been invalidated.");
469 const MachineLoop *Loop = getLoopFor(MBB);
470 const MachineLoop *SuccLoop = getLoopFor(TBI.Succ);
471 assert(!(Loop && Loop == SuccLoop && TBI.Succ == Loop->getHeader()) &&
472 "Trace contains backedge");
478 MachineTraceMetrics::Trace
479 MachineTraceMetrics::Ensemble::getTrace(const MachineBasicBlock *MBB) {
480 // FIXME: Check cache tags, recompute as needed.
482 return Trace(*this, BlockInfo[MBB->getNumber()]);
485 void MachineTraceMetrics::Ensemble::print(raw_ostream &OS) const {
486 OS << getName() << " ensemble:\n";
487 for (unsigned i = 0, e = BlockInfo.size(); i != e; ++i) {
488 OS << " BB#" << i << '\t';
489 BlockInfo[i].print(OS);
494 void MachineTraceMetrics::TraceBlockInfo::print(raw_ostream &OS) const {
495 if (hasValidDepth()) {
496 OS << "depth=" << InstrDepth;
498 OS << " pred=BB#" << Pred->getNumber();
501 OS << " head=BB#" << Head;
503 OS << "depth invalid";
505 if (hasValidHeight()) {
506 OS << "height=" << InstrHeight;
508 OS << " succ=BB#" << Succ->getNumber();
511 OS << " tail=BB#" << Tail;
513 OS << "height invalid";
516 void MachineTraceMetrics::Trace::print(raw_ostream &OS) const {
517 unsigned MBBNum = &TBI - &TE.BlockInfo[0];
519 OS << TE.getName() << " trace BB#" << TBI.Head << " --> BB#" << MBBNum
520 << " --> BB#" << TBI.Tail << ':';
521 if (TBI.hasValidHeight() && TBI.hasValidDepth())
522 OS << ' ' << getInstrCount() << " instrs.";
524 const MachineTraceMetrics::TraceBlockInfo *Block = &TBI;
525 OS << "\nBB#" << MBBNum;
526 while (Block->hasValidDepth() && Block->Pred) {
527 unsigned Num = Block->Pred->getNumber();
528 OS << " <- BB#" << Num;
529 Block = &TE.BlockInfo[Num];
534 while (Block->hasValidHeight() && Block->Succ) {
535 unsigned Num = Block->Succ->getNumber();
536 OS << " -> BB#" << Num;
537 Block = &TE.BlockInfo[Num];