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 &MF) {
48 TII = MF.getTarget().getInstrInfo();
49 TRI = MF.getTarget().getRegisterInfo();
50 MRI = &MF.getRegInfo();
51 Loops = &getAnalysis<MachineLoopInfo>();
52 unsigned NumBlocks = MF.getNumBlockIDs();
53 BlockInfo.resize(NumBlocks);
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 /// Is MI an instruction that should be considered free because it will likely
73 /// be eliminated by later passes?
74 static bool isFree(const MachineInstr *MI) {
75 switch(MI->getOpcode()) {
76 default: return false;
77 case TargetOpcode::PHI:
78 case TargetOpcode::PROLOG_LABEL:
79 case TargetOpcode::EH_LABEL:
80 case TargetOpcode::GC_LABEL:
81 case TargetOpcode::KILL:
82 case TargetOpcode::EXTRACT_SUBREG:
83 case TargetOpcode::INSERT_SUBREG:
84 case TargetOpcode::IMPLICIT_DEF:
85 case TargetOpcode::SUBREG_TO_REG:
86 case TargetOpcode::COPY_TO_REGCLASS:
87 case TargetOpcode::DBG_VALUE:
88 case TargetOpcode::REG_SEQUENCE:
89 case TargetOpcode::COPY:
94 /// Compute the resource usage in basic block MBB.
95 const MachineTraceMetrics::FixedBlockInfo*
96 MachineTraceMetrics::getResources(const MachineBasicBlock *MBB) {
97 assert(MBB && "No basic block");
98 FixedBlockInfo *FBI = &BlockInfo[MBB->getNumber()];
99 if (FBI->hasResources())
102 // Compute resource usage in the block.
103 // FIXME: Compute per-functional unit counts.
104 FBI->HasCalls = false;
105 unsigned InstrCount = 0;
106 for (MachineBasicBlock::const_iterator I = MBB->begin(), E = MBB->end();
108 const MachineInstr *MI = I;
113 FBI->HasCalls = true;
115 FBI->InstrCount = InstrCount;
119 //===----------------------------------------------------------------------===//
120 // Ensemble utility functions
121 //===----------------------------------------------------------------------===//
123 MachineTraceMetrics::Ensemble::Ensemble(MachineTraceMetrics *ct)
125 BlockInfo.resize(CT.BlockInfo.size());
128 // Virtual destructor serves as an anchor.
129 MachineTraceMetrics::Ensemble::~Ensemble() {}
132 MachineTraceMetrics::Ensemble::getLoopFor(const MachineBasicBlock *MBB) {
133 return CT.Loops->getLoopFor(MBB);
136 // Update resource-related information in the TraceBlockInfo for MBB.
137 // Only update resources related to the trace above MBB.
138 void MachineTraceMetrics::Ensemble::
139 computeDepthResources(const MachineBasicBlock *MBB) {
140 TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()];
142 // Compute resources from trace above. The top block is simple.
148 // Compute from the block above. A post-order traversal ensures the
149 // predecessor is always computed first.
150 TraceBlockInfo *PredTBI = &BlockInfo[TBI->Pred->getNumber()];
151 assert(PredTBI->hasValidDepth() && "Trace above has not been computed yet");
152 const FixedBlockInfo *PredFBI = CT.getResources(TBI->Pred);
153 TBI->InstrDepth = PredTBI->InstrDepth + PredFBI->InstrCount;
156 // Update resource-related information in the TraceBlockInfo for MBB.
157 // Only update resources related to the trace below MBB.
158 void MachineTraceMetrics::Ensemble::
159 computeHeightResources(const MachineBasicBlock *MBB) {
160 TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()];
162 // Compute resources for the current block.
163 TBI->InstrHeight = CT.getResources(MBB)->InstrCount;
165 // The trace tail is done.
169 // Compute from the block below. A post-order traversal ensures the
170 // predecessor is always computed first.
171 TraceBlockInfo *SuccTBI = &BlockInfo[TBI->Succ->getNumber()];
172 assert(SuccTBI->hasValidHeight() && "Trace below has not been computed yet");
173 TBI->InstrHeight += SuccTBI->InstrHeight;
176 // Check if depth resources for MBB are valid and return the TBI.
177 // Return NULL if the resources have been invalidated.
178 const MachineTraceMetrics::TraceBlockInfo*
179 MachineTraceMetrics::Ensemble::
180 getDepthResources(const MachineBasicBlock *MBB) const {
181 const TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()];
182 return TBI->hasValidDepth() ? TBI : 0;
185 // Check if height resources for MBB are valid and return the TBI.
186 // Return NULL if the resources have been invalidated.
187 const MachineTraceMetrics::TraceBlockInfo*
188 MachineTraceMetrics::Ensemble::
189 getHeightResources(const MachineBasicBlock *MBB) const {
190 const TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()];
191 return TBI->hasValidHeight() ? TBI : 0;
194 //===----------------------------------------------------------------------===//
195 // Trace Selection Strategies
196 //===----------------------------------------------------------------------===//
198 // A trace selection strategy is implemented as a sub-class of Ensemble. The
199 // trace through a block B is computed by two DFS traversals of the CFG
200 // starting from B. One upwards, and one downwards. During the upwards DFS,
201 // pickTracePred() is called on the post-ordered blocks. During the downwards
202 // DFS, pickTraceSucc() is called in a post-order.
205 // MinInstrCountEnsemble - Pick the trace that executes the least number of
208 class MinInstrCountEnsemble : public MachineTraceMetrics::Ensemble {
209 const char *getName() { return "MinInstr"; }
210 const MachineBasicBlock *pickTracePred(const MachineBasicBlock*);
211 const MachineBasicBlock *pickTraceSucc(const MachineBasicBlock*);
214 MinInstrCountEnsemble(MachineTraceMetrics *ct)
215 : MachineTraceMetrics::Ensemble(ct) {}
219 // Select the preferred predecessor for MBB.
220 const MachineBasicBlock*
221 MinInstrCountEnsemble::pickTracePred(const MachineBasicBlock *MBB) {
222 if (MBB->pred_empty())
224 MachineLoop *CurLoop = getLoopFor(MBB);
225 // Don't leave loops, and never follow back-edges.
226 if (CurLoop && MBB == CurLoop->getHeader())
228 unsigned CurCount = CT.getResources(MBB)->InstrCount;
229 const MachineBasicBlock *Best = 0;
230 unsigned BestDepth = 0;
231 for (MachineBasicBlock::const_pred_iterator
232 I = MBB->pred_begin(), E = MBB->pred_end(); I != E; ++I) {
233 const MachineBasicBlock *Pred = *I;
234 const MachineTraceMetrics::TraceBlockInfo *PredTBI =
235 getDepthResources(Pred);
236 // Ignore invalidated predecessors. This never happens on the first scan,
237 // but if we rejected this predecessor earlier, it won't be revalidated.
240 // Don't consider predecessors in other loops.
241 if (getLoopFor(Pred) != CurLoop)
243 // Pick the predecessor that would give this block the smallest InstrDepth.
244 unsigned Depth = PredTBI->InstrDepth + CurCount;
245 if (!Best || Depth < BestDepth)
246 Best = Pred, BestDepth = Depth;
251 // Select the preferred successor for MBB.
252 const MachineBasicBlock*
253 MinInstrCountEnsemble::pickTraceSucc(const MachineBasicBlock *MBB) {
254 if (MBB->pred_empty())
256 MachineLoop *CurLoop = getLoopFor(MBB);
257 const MachineBasicBlock *Best = 0;
258 unsigned BestHeight = 0;
259 for (MachineBasicBlock::const_succ_iterator
260 I = MBB->succ_begin(), E = MBB->succ_end(); I != E; ++I) {
261 const MachineBasicBlock *Succ = *I;
262 const MachineTraceMetrics::TraceBlockInfo *SuccTBI =
263 getHeightResources(Succ);
264 // Ignore invalidated successors.
267 // Don't consider back-edges.
268 if (CurLoop && Succ == CurLoop->getHeader())
270 // Don't consider successors in other loops.
271 if (getLoopFor(Succ) != CurLoop)
273 // Pick the successor that would give this block the smallest InstrHeight.
274 unsigned Height = SuccTBI->InstrHeight;
275 if (!Best || Height < BestHeight)
276 Best = Succ, BestHeight = Height;
281 // Get an Ensemble sub-class for the requested trace strategy.
282 MachineTraceMetrics::Ensemble *
283 MachineTraceMetrics::getEnsemble(MachineTraceMetrics::Strategy strategy) {
284 assert(strategy < TS_NumStrategies && "Invalid trace strategy enum");
285 Ensemble *&E = Ensembles[strategy];
289 // Allocate new Ensemble on demand.
291 case TS_MinInstrCount: return (E = new MinInstrCountEnsemble(this));
292 default: llvm_unreachable("Invalid trace strategy enum");
296 void MachineTraceMetrics::invalidate(const MachineBasicBlock *MBB) {
297 DEBUG(dbgs() << "Invalidate traces through BB#" << MBB->getNumber() << '\n');
298 BlockInfo[MBB->getNumber()].invalidate();
299 for (unsigned i = 0; i != TS_NumStrategies; ++i)
301 Ensembles[i]->invalidate(MBB);
304 //===----------------------------------------------------------------------===//
306 //===----------------------------------------------------------------------===//
308 // Traces are built by two CFG traversals. To avoid recomputing too much, use a
309 // set abstraction that confines the search to the current loop, and doesn't
314 MutableArrayRef<MachineTraceMetrics::TraceBlockInfo> Blocks;
315 const MachineLoopInfo *Loops;
316 const MachineLoop *CurLoop;
318 LoopBounds(MutableArrayRef<MachineTraceMetrics::TraceBlockInfo> blocks,
319 const MachineLoopInfo *loops, const MachineLoop *curloop)
320 : Blocks(blocks), Loops(loops), CurLoop(curloop), Downward(false) {}
324 // Specialize po_iterator_storage in order to prune the post-order traversal so
325 // it is limited to the current loop and doesn't traverse the loop back edges.
328 class po_iterator_storage<LoopBounds, true> {
331 po_iterator_storage(LoopBounds &lb) : LB(lb) {}
332 void finishPostorder(const MachineBasicBlock*) {}
334 bool insertEdge(const MachineBasicBlock *From, const MachineBasicBlock *To) {
335 // Skip already visited To blocks.
336 MachineTraceMetrics::TraceBlockInfo &TBI = LB.Blocks[To->getNumber()];
337 if (LB.Downward ? TBI.hasValidHeight() : TBI.hasValidDepth())
339 // Don't follow CurLoop backedges.
340 if (LB.CurLoop && (LB.Downward ? To : From) == LB.CurLoop->getHeader())
342 // Don't leave CurLoop.
343 if (LB.Loops->getLoopFor(To) != LB.CurLoop)
345 // This is a new block. The PO traversal will compute height/depth
346 // resources, causing us to reject new edges to To. This only works because
347 // we reject back-edges, so the CFG is cycle-free.
353 /// Compute the trace through MBB.
354 void MachineTraceMetrics::Ensemble::computeTrace(const MachineBasicBlock *MBB) {
355 DEBUG(dbgs() << "Computing " << getName() << " trace through BB#"
356 << MBB->getNumber() << '\n');
357 // Set up loop bounds for the backwards post-order traversal.
358 LoopBounds Bounds(BlockInfo, CT.Loops, getLoopFor(MBB));
360 // Run an upwards post-order search for the trace start.
361 Bounds.Downward = false;
362 typedef ipo_ext_iterator<const MachineBasicBlock*, LoopBounds> UpwardPO;
363 for (UpwardPO I = ipo_ext_begin(MBB, Bounds), E = ipo_ext_end(MBB, Bounds);
365 DEBUG(dbgs() << " pred for BB#" << I->getNumber() << ": ");
366 TraceBlockInfo &TBI = BlockInfo[I->getNumber()];
367 // All the predecessors have been visited, pick the preferred one.
368 TBI.Pred = pickTracePred(*I);
371 dbgs() << "BB#" << TBI.Pred->getNumber() << '\n';
375 // The trace leading to I is now known, compute the depth resources.
376 computeDepthResources(*I);
379 // Run a downwards post-order search for the trace end.
380 Bounds.Downward = true;
381 typedef po_ext_iterator<const MachineBasicBlock*, LoopBounds> DownwardPO;
382 for (DownwardPO I = po_ext_begin(MBB, Bounds), E = po_ext_end(MBB, Bounds);
384 DEBUG(dbgs() << " succ for BB#" << I->getNumber() << ": ");
385 TraceBlockInfo &TBI = BlockInfo[I->getNumber()];
386 // All the successors have been visited, pick the preferred one.
387 TBI.Succ = pickTraceSucc(*I);
390 dbgs() << "BB#" << TBI.Succ->getNumber() << '\n';
394 // The trace leaving I is now known, compute the height resources.
395 computeHeightResources(*I);
399 /// Invalidate traces through BadMBB.
401 MachineTraceMetrics::Ensemble::invalidate(const MachineBasicBlock *BadMBB) {
402 SmallVector<const MachineBasicBlock*, 16> WorkList;
403 TraceBlockInfo &BadTBI = BlockInfo[BadMBB->getNumber()];
405 // Invalidate height resources of blocks above MBB.
406 if (BadTBI.hasValidHeight()) {
407 BadTBI.invalidateHeight();
408 WorkList.push_back(BadMBB);
410 const MachineBasicBlock *MBB = WorkList.pop_back_val();
411 DEBUG(dbgs() << "Invalidate BB#" << MBB->getNumber() << ' ' << getName()
413 // Find any MBB predecessors that have MBB as their preferred successor.
414 // They are the only ones that need to be invalidated.
415 for (MachineBasicBlock::const_pred_iterator
416 I = MBB->pred_begin(), E = MBB->pred_end(); I != E; ++I) {
417 TraceBlockInfo &TBI = BlockInfo[(*I)->getNumber()];
418 if (TBI.hasValidHeight() && TBI.Succ == MBB) {
419 TBI.invalidateHeight();
420 WorkList.push_back(*I);
423 } while (!WorkList.empty());
426 // Invalidate depth resources of blocks below MBB.
427 if (BadTBI.hasValidDepth()) {
428 BadTBI.invalidateDepth();
429 WorkList.push_back(BadMBB);
431 const MachineBasicBlock *MBB = WorkList.pop_back_val();
432 DEBUG(dbgs() << "Invalidate BB#" << MBB->getNumber() << ' ' << getName()
434 // Find any MBB successors that have MBB as their preferred predecessor.
435 // They are the only ones that need to be invalidated.
436 for (MachineBasicBlock::const_succ_iterator
437 I = MBB->succ_begin(), E = MBB->succ_end(); I != E; ++I) {
438 TraceBlockInfo &TBI = BlockInfo[(*I)->getNumber()];
439 if (TBI.hasValidDepth() && TBI.Pred == MBB) {
440 TBI.invalidateDepth();
441 WorkList.push_back(*I);
444 } while (!WorkList.empty());
449 MachineTraceMetrics::Trace
450 MachineTraceMetrics::Ensemble::getTrace(const MachineBasicBlock *MBB) {
451 // FIXME: Check cache tags, recompute as needed.
453 return Trace(*this, BlockInfo[MBB->getNumber()]);
456 void MachineTraceMetrics::Trace::print(raw_ostream &OS) const {
457 OS << TE.getName() << " trace:";
458 if (TBI.hasValidHeight() && TBI.hasValidDepth())
459 OS << ' ' << getInstrCount() << " instrs.";
461 const MachineTraceMetrics::TraceBlockInfo *Block = &TBI;
463 while (Block->hasValidDepth() && Block->Pred) {
464 unsigned Num = Block->Pred->getNumber();
465 OS << " <- BB#" << Num;
466 Block = &TE.BlockInfo[Num];
471 while (Block->hasValidHeight() && Block->Succ) {
472 unsigned Num = Block->Succ->getNumber();
473 OS << " -> BB#" << Num;
474 Block = &TE.BlockInfo[Num];