1 //===- CodeExtractor.cpp - Pull code region into a new function -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the interface to tear out a code region, such as an
11 // individual loop or a parallel section, into a new function, replacing it with
12 // a call to the new function.
14 //===----------------------------------------------------------------------===//
16 #include "llvm/Transforms/Utils/FunctionUtils.h"
17 #include "llvm/Constants.h"
18 #include "llvm/DerivedTypes.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Module.h"
21 #include "llvm/Pass.h"
22 #include "llvm/Analysis/Dominators.h"
23 #include "llvm/Analysis/LoopInfo.h"
24 #include "llvm/Analysis/Verifier.h"
25 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
26 #include "Support/Debug.h"
27 #include "Support/StringExtras.h"
34 /// getFunctionArg - Return a pointer to F's ARGNOth argument.
36 Argument *getFunctionArg(Function *F, unsigned argno) {
37 Function::aiterator I = F->abegin();
38 std::advance(I, argno);
43 typedef std::vector<Value*> Values;
44 typedef std::vector<std::pair<unsigned, unsigned> > PhiValChangesTy;
45 typedef std::map<PHINode*, PhiValChangesTy> PhiVal2ArgTy;
46 PhiVal2ArgTy PhiVal2Arg;
47 std::set<BasicBlock*> BlocksToExtract;
50 CodeExtractor(DominatorSet *ds = 0) : DS(ds) {}
52 Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code);
55 void findInputsOutputs(Values &inputs, Values &outputs,
56 BasicBlock *newHeader,
57 BasicBlock *newRootNode);
59 void processPhiNodeInputs(PHINode *Phi,
61 BasicBlock *newHeader,
62 BasicBlock *newRootNode);
64 void rewritePhiNodes(Function *F, BasicBlock *newFuncRoot);
66 Function *constructFunction(const Values &inputs,
67 const Values &outputs,
68 BasicBlock *newRootNode, BasicBlock *newHeader,
69 Function *oldFunction, Module *M);
71 void moveCodeToFunction(Function *newFunction);
73 void emitCallAndSwitchStatement(Function *newFunction,
74 BasicBlock *newHeader,
81 void CodeExtractor::processPhiNodeInputs(PHINode *Phi,
83 BasicBlock *codeReplacer,
84 BasicBlock *newFuncRoot) {
85 // Separate incoming values and BasicBlocks as internal/external. We ignore
86 // the case where both the value and BasicBlock are internal, because we don't
87 // need to do a thing.
88 std::vector<unsigned> EValEBB;
89 std::vector<unsigned> EValIBB;
90 std::vector<unsigned> IValEBB;
92 for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
93 Value *phiVal = Phi->getIncomingValue(i);
94 if (Instruction *Inst = dyn_cast<Instruction>(phiVal)) {
95 if (BlocksToExtract.count(Inst->getParent())) {
96 if (!BlocksToExtract.count(Phi->getIncomingBlock(i)))
99 if (BlocksToExtract.count(Phi->getIncomingBlock(i)))
100 EValIBB.push_back(i);
102 EValEBB.push_back(i);
104 } else if (Argument *Arg = dyn_cast<Argument>(phiVal)) {
105 // arguments are external
106 if (BlocksToExtract.count(Phi->getIncomingBlock(i)))
107 EValIBB.push_back(i);
109 EValEBB.push_back(i);
111 // Globals/Constants are internal, but considered `external' if they are
112 // coming from an external block.
113 if (!BlocksToExtract.count(Phi->getIncomingBlock(i)))
114 EValEBB.push_back(i);
118 // Both value and block are external. Need to group all of these, have an
119 // external phi, pass the result as an argument, and have THIS phi use that
121 if (EValEBB.size() > 0) {
122 if (EValEBB.size() == 1) {
123 // Now if it's coming from the newFuncRoot, it's that funky input
124 unsigned phiIdx = EValEBB[0];
125 if (!isa<Constant>(Phi->getIncomingValue(phiIdx))) {
126 PhiVal2Arg[Phi].push_back(std::make_pair(phiIdx, inputs.size()));
127 // We can just pass this value in as argument
128 inputs.push_back(Phi->getIncomingValue(phiIdx));
130 Phi->setIncomingBlock(phiIdx, newFuncRoot);
132 PHINode *externalPhi = new PHINode(Phi->getType(), "extPhi");
133 codeReplacer->getInstList().insert(codeReplacer->begin(), externalPhi);
134 for (std::vector<unsigned>::iterator i = EValEBB.begin(),
135 e = EValEBB.end(); i != e; ++i) {
136 externalPhi->addIncoming(Phi->getIncomingValue(*i),
137 Phi->getIncomingBlock(*i));
139 // We make these values invalid instead of deleting them because that
140 // would shift the indices of other values... The fixPhiNodes should
141 // clean these phi nodes up later.
142 Phi->setIncomingValue(*i, 0);
143 Phi->setIncomingBlock(*i, 0);
145 PhiVal2Arg[Phi].push_back(std::make_pair(Phi->getNumIncomingValues(),
147 // We can just pass this value in as argument
148 inputs.push_back(externalPhi);
152 // When the value is external, but block internal... just pass it in as
153 // argument, no change to phi node
154 for (std::vector<unsigned>::iterator i = EValIBB.begin(),
155 e = EValIBB.end(); i != e; ++i) {
156 // rewrite the phi input node to be an argument
157 PhiVal2Arg[Phi].push_back(std::make_pair(*i, inputs.size()));
158 inputs.push_back(Phi->getIncomingValue(*i));
161 // Value internal, block external this can happen if we are extracting a part
163 for (std::vector<unsigned>::iterator i = IValEBB.begin(),
164 e = IValEBB.end(); i != e; ++i) {
165 assert(0 && "Cannot (YET) handle internal values via external blocks");
170 void CodeExtractor::findInputsOutputs(Values &inputs, Values &outputs,
171 BasicBlock *newHeader,
172 BasicBlock *newRootNode) {
173 for (std::set<BasicBlock*>::const_iterator ci = BlocksToExtract.begin(),
174 ce = BlocksToExtract.end(); ci != ce; ++ci) {
175 BasicBlock *BB = *ci;
176 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
177 // If a used value is defined outside the region, it's an input. If an
178 // instruction is used outside the region, it's an output.
179 if (PHINode *Phi = dyn_cast<PHINode>(I)) {
180 processPhiNodeInputs(Phi, inputs, newHeader, newRootNode);
182 // All other instructions go through the generic input finder
183 // Loop over the operands of each instruction (inputs)
184 for (User::op_iterator op = I->op_begin(), opE = I->op_end();
186 if (Instruction *opI = dyn_cast<Instruction>(*op)) {
187 // Check if definition of this operand is within the loop
188 if (!BlocksToExtract.count(opI->getParent()))
189 inputs.push_back(opI);
190 } else if (isa<Argument>(*op)) {
191 inputs.push_back(*op);
195 // Consider uses of this instruction (outputs)
196 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
198 if (!BlocksToExtract.count(cast<Instruction>(*UI)->getParent())) {
199 outputs.push_back(I);
203 } // for: basic blocks
206 void CodeExtractor::rewritePhiNodes(Function *F,
207 BasicBlock *newFuncRoot) {
208 // Write any changes that were saved before: use function arguments as inputs
209 for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
211 PHINode *phi = i->first;
212 PhiValChangesTy &values = i->second;
213 for (unsigned cIdx = 0, ce = values.size(); cIdx != ce; ++cIdx)
215 unsigned phiValueIdx = values[cIdx].first, argNum = values[cIdx].second;
216 if (phiValueIdx < phi->getNumIncomingValues())
217 phi->setIncomingValue(phiValueIdx, getFunctionArg(F, argNum));
219 phi->addIncoming(getFunctionArg(F, argNum), newFuncRoot);
223 // Delete any invalid Phi node inputs that were marked as NULL previously
224 for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
226 PHINode *phi = i->first;
227 for (unsigned idx = 0, end = phi->getNumIncomingValues(); idx != end; ++idx)
229 if (phi->getIncomingValue(idx) == 0 && phi->getIncomingBlock(idx) == 0) {
230 phi->removeIncomingValue(idx);
237 // We are done with the saved values
242 /// constructFunction - make a function based on inputs and outputs, as follows:
243 /// f(in0, ..., inN, out0, ..., outN)
245 Function *CodeExtractor::constructFunction(const Values &inputs,
246 const Values &outputs,
247 BasicBlock *newRootNode,
248 BasicBlock *newHeader,
249 Function *oldFunction, Module *M) {
250 DEBUG(std::cerr << "inputs: " << inputs.size() << "\n");
251 DEBUG(std::cerr << "outputs: " << outputs.size() << "\n");
252 BasicBlock *header = *BlocksToExtract.begin();
254 // This function returns unsigned, outputs will go back by reference.
255 Type *retTy = Type::UShortTy;
256 std::vector<const Type*> paramTy;
258 // Add the types of the input values to the function's argument list
259 for (Values::const_iterator i = inputs.begin(),
260 e = inputs.end(); i != e; ++i) {
261 const Value *value = *i;
262 DEBUG(std::cerr << "value used in func: " << value << "\n");
263 paramTy.push_back(value->getType());
266 // Add the types of the output values to the function's argument list.
267 for (Values::const_iterator I = outputs.begin(), E = outputs.end();
269 DEBUG(std::cerr << "instr used in func: " << *I << "\n");
270 paramTy.push_back(PointerType::get((*I)->getType()));
273 DEBUG(std::cerr << "Function type: " << retTy << " f(");
274 for (std::vector<const Type*>::iterator i = paramTy.begin(),
275 e = paramTy.end(); i != e; ++i)
276 DEBUG(std::cerr << *i << ", ");
277 DEBUG(std::cerr << ")\n");
279 const FunctionType *funcType = FunctionType::get(retTy, paramTy, false);
281 // Create the new function
282 Function *newFunction = new Function(funcType,
283 GlobalValue::InternalLinkage,
284 oldFunction->getName() + "_code", M);
285 newFunction->getBasicBlockList().push_back(newRootNode);
287 // Create an iterator to name all of the arguments we inserted.
288 Function::aiterator AI = newFunction->abegin();
290 // Rewrite all users of the inputs in the extracted region to use the
291 // arguments instead.
292 for (unsigned i = 0, e = inputs.size(); i != e; ++i, ++AI) {
293 AI->setName(inputs[i]->getName());
294 std::vector<User*> Users(inputs[i]->use_begin(), inputs[i]->use_end());
295 for (std::vector<User*>::iterator use = Users.begin(), useE = Users.end();
297 if (Instruction* inst = dyn_cast<Instruction>(*use))
298 if (BlocksToExtract.count(inst->getParent()))
299 inst->replaceUsesOfWith(inputs[i], AI);
302 // Set names for all of the output arguments.
303 for (unsigned i = 0, e = outputs.size(); i != e; ++i, ++AI)
304 AI->setName(outputs[i]->getName()+".out");
307 // Rewrite branches to basic blocks outside of the loop to new dummy blocks
308 // within the new function. This must be done before we lose track of which
309 // blocks were originally in the code region.
310 std::vector<User*> Users(header->use_begin(), header->use_end());
311 for (std::vector<User*>::iterator i = Users.begin(), e = Users.end();
313 if (BranchInst *inst = dyn_cast<BranchInst>(*i)) {
314 BasicBlock *BB = inst->getParent();
315 if (!BlocksToExtract.count(BB) && BB->getParent() == oldFunction) {
316 // The BasicBlock which contains the branch is not in the region
317 // modify the branch target to a new block
318 inst->replaceUsesOfWith(header, newHeader);
326 void CodeExtractor::moveCodeToFunction(Function *newFunction) {
327 Function *oldFunc = (*BlocksToExtract.begin())->getParent();
328 Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList();
329 Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList();
331 for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
332 e = BlocksToExtract.end(); i != e; ++i) {
333 // Delete the basic block from the old function, and the list of blocks
334 oldBlocks.remove(*i);
336 // Insert this basic block into the new function
337 newBlocks.push_back(*i);
342 CodeExtractor::emitCallAndSwitchStatement(Function *newFunction,
343 BasicBlock *codeReplacer,
346 // Emit a call to the new function, passing allocated memory for outputs and
347 // just plain inputs for non-scalars
348 std::vector<Value*> params(inputs);
350 // Get an iterator to the first output argument.
351 Function::aiterator OutputArgBegin = newFunction->abegin();
352 std::advance(OutputArgBegin, inputs.size());
354 for (unsigned i = 0, e = outputs.size(); i != e; ++i) {
355 Value *Output = outputs[i];
356 // Create allocas for scalar outputs
358 new AllocaInst(outputs[i]->getType(), 0, Output->getName()+".loc",
359 codeReplacer->getParent()->begin()->begin());
360 params.push_back(alloca);
362 LoadInst *load = new LoadInst(alloca, Output->getName()+".reload");
363 codeReplacer->getInstList().push_back(load);
364 std::vector<User*> Users(outputs[i]->use_begin(), outputs[i]->use_end());
365 for (unsigned u = 0, e = Users.size(); u != e; ++u) {
366 Instruction *inst = cast<Instruction>(Users[u]);
367 if (!BlocksToExtract.count(inst->getParent()))
368 inst->replaceUsesOfWith(outputs[i], load);
372 CallInst *call = new CallInst(newFunction, params, "targetBlock");
373 codeReplacer->getInstList().push_front(call);
375 // Now we can emit a switch statement using the call as a value.
376 SwitchInst *TheSwitch = new SwitchInst(call, codeReplacer, codeReplacer);
378 // Since there may be multiple exits from the original region, make the new
379 // function return an unsigned, switch on that number. This loop iterates
380 // over all of the blocks in the extracted region, updating any terminator
381 // instructions in the to-be-extracted region that branch to blocks that are
382 // not in the region to be extracted.
383 std::map<BasicBlock*, BasicBlock*> ExitBlockMap;
385 unsigned switchVal = 0;
386 for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
387 e = BlocksToExtract.end(); i != e; ++i) {
388 TerminatorInst *TI = (*i)->getTerminator();
389 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
390 if (!BlocksToExtract.count(TI->getSuccessor(i))) {
391 BasicBlock *OldTarget = TI->getSuccessor(i);
392 // add a new basic block which returns the appropriate value
393 BasicBlock *&NewTarget = ExitBlockMap[OldTarget];
395 // If we don't already have an exit stub for this non-extracted
396 // destination, create one now!
397 NewTarget = new BasicBlock(OldTarget->getName() + ".exitStub",
400 ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal++);
401 ReturnInst *NTRet = new ReturnInst(brVal, NewTarget);
403 // Update the switch instruction.
404 TheSwitch->addCase(brVal, OldTarget);
406 // Restore values just before we exit
407 // FIXME: Use a GetElementPtr to bunch the outputs in a struct
408 Function::aiterator OAI = OutputArgBegin;
409 for (unsigned out = 0, e = outputs.size(); out != e; ++out, ++OAI)
411 DS->dominates(cast<Instruction>(outputs[out])->getParent(),
413 new StoreInst(outputs[out], OAI, NTRet);
416 // rewrite the original branch instruction with this new target
417 TI->setSuccessor(i, NewTarget);
421 // Now that we've done the deed, make the default destination of the switch
422 // instruction be one of the exit blocks of the region.
423 if (TheSwitch->getNumSuccessors() > 1) {
424 // FIXME: this is broken w.r.t. PHI nodes, but the old code was more broken.
425 // This edge is not traversable.
426 TheSwitch->setSuccessor(0, TheSwitch->getSuccessor(1));
431 /// ExtractRegion - Removes a loop from a function, replaces it with a call to
432 /// new function. Returns pointer to the new function.
436 /// find inputs and outputs for the region
438 /// for inputs: add to function as args, map input instr* to arg#
439 /// for outputs: add allocas for scalars,
440 /// add to func as args, map output instr* to arg#
442 /// rewrite func to use argument #s instead of instr*
444 /// for each scalar output in the function: at every exit, store intermediate
445 /// computed result back into memory.
447 Function *CodeExtractor::ExtractCodeRegion(const std::vector<BasicBlock*> &code)
449 // 1) Find inputs, outputs
450 // 2) Construct new function
451 // * Add allocas for defs, pass as args by reference
452 // * Pass in uses as args
453 // 3) Move code region, add call instr to func
455 BlocksToExtract.insert(code.begin(), code.end());
457 Values inputs, outputs;
459 // Assumption: this is a single-entry code region, and the header is the first
460 // block in the region.
461 BasicBlock *header = code[0];
462 for (unsigned i = 1, e = code.size(); i != e; ++i)
463 for (pred_iterator PI = pred_begin(code[i]), E = pred_end(code[i]);
465 assert(BlocksToExtract.count(*PI) &&
466 "No blocks in this region may have entries from outside the region"
467 " except for the first block!");
469 Function *oldFunction = header->getParent();
471 // This takes place of the original loop
472 BasicBlock *codeReplacer = new BasicBlock("codeRepl", oldFunction);
474 // The new function needs a root node because other nodes can branch to the
475 // head of the loop, and the root cannot have predecessors
476 BasicBlock *newFuncRoot = new BasicBlock("newFuncRoot");
477 newFuncRoot->getInstList().push_back(new BranchInst(header));
479 // Find inputs to, outputs from the code region
481 // If one of the inputs is coming from a different basic block and it's in a
482 // phi node, we need to rewrite the phi node:
484 // * All the inputs which involve basic blocks OUTSIDE of this region go into
485 // a NEW phi node that takes care of finding which value really came in.
486 // The result of this phi is passed to the function as an argument.
488 // * All the other phi values stay.
490 // FIXME: PHI nodes' incoming blocks aren't being rewritten to accomodate for
491 // blocks moving to a new function.
492 // SOLUTION: move Phi nodes out of the loop header into the codeReplacer, pass
493 // the values as parameters to the function
494 findInputsOutputs(inputs, outputs, codeReplacer, newFuncRoot);
496 // Step 2: Construct new function based on inputs/outputs,
497 // Add allocas for all defs
498 Function *newFunction = constructFunction(inputs, outputs, newFuncRoot,
499 codeReplacer, oldFunction,
500 oldFunction->getParent());
502 rewritePhiNodes(newFunction, newFuncRoot);
504 emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);
506 moveCodeToFunction(newFunction);
508 DEBUG(if (verifyFunction(*newFunction)) abort());
512 /// ExtractCodeRegion - slurp a sequence of basic blocks into a brand new
515 Function* llvm::ExtractCodeRegion(DominatorSet &DS,
516 const std::vector<BasicBlock*> &code) {
517 return CodeExtractor(&DS).ExtractCodeRegion(code);
520 /// ExtractBasicBlock - slurp a natural loop into a brand new function
522 Function* llvm::ExtractLoop(DominatorSet &DS, Loop *L) {
523 return CodeExtractor(&DS).ExtractCodeRegion(L->getBlocks());
526 /// ExtractBasicBlock - slurp a basic block into a brand new function
528 Function* llvm::ExtractBasicBlock(BasicBlock *BB) {
529 std::vector<BasicBlock*> Blocks;
530 Blocks.push_back(BB);
531 return CodeExtractor().ExtractCodeRegion(Blocks);