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/BasicBlock.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/LoopInfo.h"
23 #include "llvm/Analysis/Verifier.h"
24 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
25 #include "llvm/Transforms/Utils/FunctionUtils.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);
42 struct CodeExtractor {
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;
49 Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code);
52 void findInputsOutputs(Values &inputs, Values &outputs,
53 BasicBlock *newHeader,
54 BasicBlock *newRootNode);
56 void processPhiNodeInputs(PHINode *Phi,
58 BasicBlock *newHeader,
59 BasicBlock *newRootNode);
61 void rewritePhiNodes(Function *F, BasicBlock *newFuncRoot);
63 Function *constructFunction(const Values &inputs,
64 const Values &outputs,
65 BasicBlock *newRootNode, BasicBlock *newHeader,
66 Function *oldFunction, Module *M);
68 void moveCodeToFunction(Function *newFunction);
70 void emitCallAndSwitchStatement(Function *newFunction,
71 BasicBlock *newHeader,
78 void CodeExtractor::processPhiNodeInputs(PHINode *Phi,
80 BasicBlock *codeReplacer,
81 BasicBlock *newFuncRoot) {
82 // Separate incoming values and BasicBlocks as internal/external. We ignore
83 // the case where both the value and BasicBlock are internal, because we don't
84 // need to do a thing.
85 std::vector<unsigned> EValEBB;
86 std::vector<unsigned> EValIBB;
87 std::vector<unsigned> IValEBB;
89 for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
90 Value *phiVal = Phi->getIncomingValue(i);
91 if (Instruction *Inst = dyn_cast<Instruction>(phiVal)) {
92 if (BlocksToExtract.count(Inst->getParent())) {
93 if (!BlocksToExtract.count(Phi->getIncomingBlock(i)))
96 if (BlocksToExtract.count(Phi->getIncomingBlock(i)))
101 } else if (Argument *Arg = dyn_cast<Argument>(phiVal)) {
102 // arguments are external
103 if (BlocksToExtract.count(Phi->getIncomingBlock(i)))
104 EValIBB.push_back(i);
106 EValEBB.push_back(i);
108 // Globals/Constants are internal, but considered `external' if they are
109 // coming from an external block.
110 if (!BlocksToExtract.count(Phi->getIncomingBlock(i)))
111 EValEBB.push_back(i);
115 // Both value and block are external. Need to group all of these, have an
116 // external phi, pass the result as an argument, and have THIS phi use that
118 if (EValEBB.size() > 0) {
119 if (EValEBB.size() == 1) {
120 // Now if it's coming from the newFuncRoot, it's that funky input
121 unsigned phiIdx = EValEBB[0];
122 if (!isa<Constant>(Phi->getIncomingValue(phiIdx))) {
123 PhiVal2Arg[Phi].push_back(std::make_pair(phiIdx, inputs.size()));
124 // We can just pass this value in as argument
125 inputs.push_back(Phi->getIncomingValue(phiIdx));
127 Phi->setIncomingBlock(phiIdx, newFuncRoot);
129 PHINode *externalPhi = new PHINode(Phi->getType(), "extPhi");
130 codeReplacer->getInstList().insert(codeReplacer->begin(), externalPhi);
131 for (std::vector<unsigned>::iterator i = EValEBB.begin(),
132 e = EValEBB.end(); i != e; ++i) {
133 externalPhi->addIncoming(Phi->getIncomingValue(*i),
134 Phi->getIncomingBlock(*i));
136 // We make these values invalid instead of deleting them because that
137 // would shift the indices of other values... The fixPhiNodes should
138 // clean these phi nodes up later.
139 Phi->setIncomingValue(*i, 0);
140 Phi->setIncomingBlock(*i, 0);
142 PhiVal2Arg[Phi].push_back(std::make_pair(Phi->getNumIncomingValues(),
144 // We can just pass this value in as argument
145 inputs.push_back(externalPhi);
149 // When the value is external, but block internal... just pass it in as
150 // argument, no change to phi node
151 for (std::vector<unsigned>::iterator i = EValIBB.begin(),
152 e = EValIBB.end(); i != e; ++i) {
153 // rewrite the phi input node to be an argument
154 PhiVal2Arg[Phi].push_back(std::make_pair(*i, inputs.size()));
155 inputs.push_back(Phi->getIncomingValue(*i));
158 // Value internal, block external this can happen if we are extracting a part
160 for (std::vector<unsigned>::iterator i = IValEBB.begin(),
161 e = IValEBB.end(); i != e; ++i) {
162 assert(0 && "Cannot (YET) handle internal values via external blocks");
167 void CodeExtractor::findInputsOutputs(Values &inputs, Values &outputs,
168 BasicBlock *newHeader,
169 BasicBlock *newRootNode) {
170 for (std::set<BasicBlock*>::const_iterator ci = BlocksToExtract.begin(),
171 ce = BlocksToExtract.end(); ci != ce; ++ci) {
172 BasicBlock *BB = *ci;
173 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
174 // If a used value is defined outside the region, it's an input. If an
175 // instruction is used outside the region, it's an output.
176 if (PHINode *Phi = dyn_cast<PHINode>(I)) {
177 processPhiNodeInputs(Phi, inputs, newHeader, newRootNode);
179 // All other instructions go through the generic input finder
180 // Loop over the operands of each instruction (inputs)
181 for (User::op_iterator op = I->op_begin(), opE = I->op_end();
183 if (Instruction *opI = dyn_cast<Instruction>(*op)) {
184 // Check if definition of this operand is within the loop
185 if (!BlocksToExtract.count(opI->getParent()))
186 inputs.push_back(opI);
187 } else if (isa<Argument>(*op)) {
188 inputs.push_back(*op);
192 // Consider uses of this instruction (outputs)
193 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
195 if (!BlocksToExtract.count(cast<Instruction>(*UI)->getParent()))
196 outputs.push_back(*UI);
198 } // for: basic blocks
201 void CodeExtractor::rewritePhiNodes(Function *F,
202 BasicBlock *newFuncRoot) {
203 // Write any changes that were saved before: use function arguments as inputs
204 for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
206 PHINode *phi = i->first;
207 PhiValChangesTy &values = i->second;
208 for (unsigned cIdx = 0, ce = values.size(); cIdx != ce; ++cIdx)
210 unsigned phiValueIdx = values[cIdx].first, argNum = values[cIdx].second;
211 if (phiValueIdx < phi->getNumIncomingValues())
212 phi->setIncomingValue(phiValueIdx, getFunctionArg(F, argNum));
214 phi->addIncoming(getFunctionArg(F, argNum), newFuncRoot);
218 // Delete any invalid Phi node inputs that were marked as NULL previously
219 for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
221 PHINode *phi = i->first;
222 for (unsigned idx = 0, end = phi->getNumIncomingValues(); idx != end; ++idx)
224 if (phi->getIncomingValue(idx) == 0 && phi->getIncomingBlock(idx) == 0) {
225 phi->removeIncomingValue(idx);
232 // We are done with the saved values
237 /// constructFunction - make a function based on inputs and outputs, as follows:
238 /// f(in0, ..., inN, out0, ..., outN)
240 Function *CodeExtractor::constructFunction(const Values &inputs,
241 const Values &outputs,
242 BasicBlock *newRootNode,
243 BasicBlock *newHeader,
244 Function *oldFunction, Module *M) {
245 DEBUG(std::cerr << "inputs: " << inputs.size() << "\n");
246 DEBUG(std::cerr << "outputs: " << outputs.size() << "\n");
247 BasicBlock *header = *BlocksToExtract.begin();
249 // This function returns unsigned, outputs will go back by reference.
250 Type *retTy = Type::UShortTy;
251 std::vector<const Type*> paramTy;
253 // Add the types of the input values to the function's argument list
254 for (Values::const_iterator i = inputs.begin(),
255 e = inputs.end(); i != e; ++i) {
256 const Value *value = *i;
257 DEBUG(std::cerr << "value used in func: " << value << "\n");
258 paramTy.push_back(value->getType());
261 // Add the types of the output values to the function's argument list, but
262 // make them pointer types for scalars
263 for (Values::const_iterator i = outputs.begin(),
264 e = outputs.end(); i != e; ++i) {
265 const Value *value = *i;
266 DEBUG(std::cerr << "instr used in func: " << value << "\n");
267 const Type *valueType = value->getType();
268 // Convert scalar types into a pointer of that type
269 if (valueType->isPrimitiveType()) {
270 valueType = PointerType::get(valueType);
272 paramTy.push_back(valueType);
275 DEBUG(std::cerr << "Function type: " << retTy << " f(");
276 for (std::vector<const Type*>::iterator i = paramTy.begin(),
277 e = paramTy.end(); i != e; ++i)
278 DEBUG(std::cerr << *i << ", ");
279 DEBUG(std::cerr << ")\n");
281 const FunctionType *funcType = FunctionType::get(retTy, paramTy, false);
283 // Create the new function
284 Function *newFunction = new Function(funcType,
285 GlobalValue::InternalLinkage,
286 oldFunction->getName() + "_code", M);
287 newFunction->getBasicBlockList().push_back(newRootNode);
289 for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
290 std::vector<User*> Users(inputs[i]->use_begin(), inputs[i]->use_end());
291 for (std::vector<User*>::iterator use = Users.begin(), useE = Users.end();
293 if (Instruction* inst = dyn_cast<Instruction>(*use))
294 if (BlocksToExtract.count(inst->getParent()))
295 inst->replaceUsesOfWith(inputs[i], getFunctionArg(newFunction, i));
298 // Rewrite branches to basic blocks outside of the loop to new dummy blocks
299 // within the new function. This must be done before we lose track of which
300 // blocks were originally in the code region.
301 std::vector<User*> Users(header->use_begin(), header->use_end());
302 for (std::vector<User*>::iterator i = Users.begin(), e = Users.end();
304 if (BranchInst *inst = dyn_cast<BranchInst>(*i)) {
305 BasicBlock *BB = inst->getParent();
306 if (!BlocksToExtract.count(BB) && BB->getParent() == oldFunction) {
307 // The BasicBlock which contains the branch is not in the region
308 // modify the branch target to a new block
309 inst->replaceUsesOfWith(header, newHeader);
317 void CodeExtractor::moveCodeToFunction(Function *newFunction) {
318 Function *oldFunc = (*BlocksToExtract.begin())->getParent();
319 Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList();
320 Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList();
322 for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
323 e = BlocksToExtract.end(); i != e; ++i) {
324 // Delete the basic block from the old function, and the list of blocks
325 oldBlocks.remove(*i);
327 // Insert this basic block into the new function
328 newBlocks.push_back(*i);
333 CodeExtractor::emitCallAndSwitchStatement(Function *newFunction,
334 BasicBlock *codeReplacer,
338 // Emit a call to the new function, passing allocated memory for outputs and
339 // just plain inputs for non-scalars
340 std::vector<Value*> params(inputs);
342 for (Values::const_iterator i = outputs.begin(), e = outputs.end(); i != e;
345 // Create allocas for scalar outputs
346 if (Output->getType()->isPrimitiveType()) {
348 new AllocaInst((*i)->getType(), 0, Output->getName()+".loc",
349 codeReplacer->getParent()->begin()->begin());
350 params.push_back(alloca);
352 LoadInst *load = new LoadInst(alloca, Output->getName()+".reload");
353 codeReplacer->getInstList().push_back(load);
354 std::vector<User*> Users((*i)->use_begin(), (*i)->use_end());
355 for (std::vector<User*>::iterator use = Users.begin(), useE =Users.end();
356 use != useE; ++use) {
357 if (Instruction* inst = dyn_cast<Instruction>(*use)) {
358 if (!BlocksToExtract.count(inst->getParent()))
359 inst->replaceUsesOfWith(*i, load);
363 params.push_back(*i);
367 CallInst *call = new CallInst(newFunction, params, "targetBlock");
368 codeReplacer->getInstList().push_front(call);
370 // Now we can emit a switch statement using the call as a value.
371 SwitchInst *TheSwitch = new SwitchInst(call, codeReplacer, codeReplacer);
373 // Since there may be multiple exits from the original region, make the new
374 // function return an unsigned, switch on that number. This loop iterates
375 // over all of the blocks in the extracted region, updating any terminator
376 // instructions in the to-be-extracted region that branch to blocks that are
377 // not in the region to be extracted.
378 std::map<BasicBlock*, BasicBlock*> ExitBlockMap;
380 unsigned switchVal = 0;
381 for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
382 e = BlocksToExtract.end(); i != e; ++i) {
383 TerminatorInst *TI = (*i)->getTerminator();
384 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
385 if (!BlocksToExtract.count(TI->getSuccessor(i))) {
386 BasicBlock *OldTarget = TI->getSuccessor(i);
387 // add a new basic block which returns the appropriate value
388 BasicBlock *&NewTarget = ExitBlockMap[OldTarget];
390 // If we don't already have an exit stub for this non-extracted
391 // destination, create one now!
392 NewTarget = new BasicBlock(OldTarget->getName() + ".exitStub",
395 ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal++);
396 ReturnInst *NTRet = new ReturnInst(brVal, NewTarget);
398 // Update the switch instruction.
399 TheSwitch->addCase(brVal, OldTarget);
401 // Restore values just before we exit
402 // FIXME: Use a GetElementPtr to bunch the outputs in a struct
403 for (unsigned out = 0, e = outputs.size(); out != e; ++out)
404 new StoreInst(outputs[out], getFunctionArg(newFunction, out),NTRet);
407 // rewrite the original branch instruction with this new target
408 TI->setSuccessor(i, NewTarget);
412 // Now that we've done the deed, make the default destination of the switch
413 // instruction be one of the exit blocks of the region.
414 if (TheSwitch->getNumSuccessors() > 1) {
415 // FIXME: this is broken w.r.t. PHI nodes, but the old code was more broken.
416 // This edge is not traversable.
417 TheSwitch->setSuccessor(0, TheSwitch->getSuccessor(1));
422 /// ExtractRegion - Removes a loop from a function, replaces it with a call to
423 /// new function. Returns pointer to the new function.
427 /// find inputs and outputs for the region
429 /// for inputs: add to function as args, map input instr* to arg#
430 /// for outputs: add allocas for scalars,
431 /// add to func as args, map output instr* to arg#
433 /// rewrite func to use argument #s instead of instr*
435 /// for each scalar output in the function: at every exit, store intermediate
436 /// computed result back into memory.
438 Function *CodeExtractor::ExtractCodeRegion(const std::vector<BasicBlock*> &code)
440 // 1) Find inputs, outputs
441 // 2) Construct new function
442 // * Add allocas for defs, pass as args by reference
443 // * Pass in uses as args
444 // 3) Move code region, add call instr to func
446 BlocksToExtract.insert(code.begin(), code.end());
448 Values inputs, outputs;
450 // Assumption: this is a single-entry code region, and the header is the first
451 // block in the region.
452 BasicBlock *header = code[0];
453 for (unsigned i = 1, e = code.size(); i != e; ++i)
454 for (pred_iterator PI = pred_begin(code[i]), E = pred_end(code[i]);
456 assert(BlocksToExtract.count(*PI) &&
457 "No blocks in this region may have entries from outside the region"
458 " except for the first block!");
460 Function *oldFunction = header->getParent();
462 // This takes place of the original loop
463 BasicBlock *codeReplacer = new BasicBlock("codeRepl", oldFunction);
465 // The new function needs a root node because other nodes can branch to the
466 // head of the loop, and the root cannot have predecessors
467 BasicBlock *newFuncRoot = new BasicBlock("newFuncRoot");
468 newFuncRoot->getInstList().push_back(new BranchInst(header));
470 // Find inputs to, outputs from the code region
472 // If one of the inputs is coming from a different basic block and it's in a
473 // phi node, we need to rewrite the phi node:
475 // * All the inputs which involve basic blocks OUTSIDE of this region go into
476 // a NEW phi node that takes care of finding which value really came in.
477 // The result of this phi is passed to the function as an argument.
479 // * All the other phi values stay.
481 // FIXME: PHI nodes' incoming blocks aren't being rewritten to accomodate for
482 // blocks moving to a new function.
483 // SOLUTION: move Phi nodes out of the loop header into the codeReplacer, pass
484 // the values as parameters to the function
485 findInputsOutputs(inputs, outputs, codeReplacer, newFuncRoot);
487 // Step 2: Construct new function based on inputs/outputs,
488 // Add allocas for all defs
489 Function *newFunction = constructFunction(inputs, outputs, newFuncRoot,
490 codeReplacer, oldFunction,
491 oldFunction->getParent());
493 rewritePhiNodes(newFunction, newFuncRoot);
495 emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);
497 moveCodeToFunction(newFunction);
499 DEBUG(if (verifyFunction(*newFunction)) abort());
503 /// ExtractCodeRegion - slurp a sequence of basic blocks into a brand new
506 Function* llvm::ExtractCodeRegion(const std::vector<BasicBlock*> &code) {
507 return CodeExtractor().ExtractCodeRegion(code);
510 /// ExtractBasicBlock - slurp a natural loop into a brand new function
512 Function* llvm::ExtractLoop(Loop *L) {
513 return CodeExtractor().ExtractCodeRegion(L->getBlocks());
516 /// ExtractBasicBlock - slurp a basic block into a brand new function
518 Function* llvm::ExtractBasicBlock(BasicBlock *BB) {
519 std::vector<BasicBlock*> Blocks;
520 Blocks.push_back(BB);
521 return CodeExtractor().ExtractCodeRegion(Blocks);