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/Transforms/Utils/BasicBlockUtils.h"
24 #include "llvm/Transforms/Utils/FunctionUtils.h"
25 #include "Support/Debug.h"
26 #include "Support/StringExtras.h"
34 inline bool contains(const std::vector<BasicBlock*> &V, const BasicBlock *BB){
35 return std::find(V.begin(), V.end(), BB) != V.end();
38 /// getFunctionArg - Return a pointer to F's ARGNOth argument.
40 Argument *getFunctionArg(Function *F, unsigned argno) {
41 Function::aiterator ai = F->abegin();
42 while (argno) { ++ai; --argno; }
46 struct CodeExtractor {
47 typedef std::vector<Value*> Values;
48 typedef std::vector<std::pair<unsigned, unsigned> > PhiValChangesTy;
49 typedef std::map<PHINode*, PhiValChangesTy> PhiVal2ArgTy;
50 PhiVal2ArgTy PhiVal2Arg;
53 Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code);
56 void findInputsOutputs(const std::vector<BasicBlock*> &code,
59 BasicBlock *newHeader,
60 BasicBlock *newRootNode);
62 void processPhiNodeInputs(PHINode *Phi,
63 const std::vector<BasicBlock*> &code,
65 BasicBlock *newHeader,
66 BasicBlock *newRootNode);
68 void rewritePhiNodes(Function *F, BasicBlock *newFuncRoot);
70 Function *constructFunction(const Values &inputs,
71 const Values &outputs,
72 BasicBlock *newRootNode, BasicBlock *newHeader,
73 const std::vector<BasicBlock*> &code,
74 Function *oldFunction, Module *M);
76 void moveCodeToFunction(const std::vector<BasicBlock*> &code,
77 Function *newFunction);
79 void emitCallAndSwitchStatement(Function *newFunction,
80 BasicBlock *newHeader,
81 const std::vector<BasicBlock*> &code,
88 void CodeExtractor::processPhiNodeInputs(PHINode *Phi,
89 const std::vector<BasicBlock*> &code,
91 BasicBlock *codeReplacer,
92 BasicBlock *newFuncRoot)
94 // Separate incoming values and BasicBlocks as internal/external. We ignore
95 // the case where both the value and BasicBlock are internal, because we don't
96 // need to do a thing.
97 std::vector<unsigned> EValEBB;
98 std::vector<unsigned> EValIBB;
99 std::vector<unsigned> IValEBB;
101 for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
102 Value *phiVal = Phi->getIncomingValue(i);
103 if (Instruction *Inst = dyn_cast<Instruction>(phiVal)) {
104 if (contains(code, Inst->getParent())) {
105 if (!contains(code, Phi->getIncomingBlock(i)))
106 IValEBB.push_back(i);
108 if (contains(code, Phi->getIncomingBlock(i)))
109 EValIBB.push_back(i);
111 EValEBB.push_back(i);
113 } else if (Constant *Const = dyn_cast<Constant>(phiVal)) {
114 // Constants are internal, but considered `external' if they are coming
115 // from an external block.
116 if (!contains(code, Phi->getIncomingBlock(i)))
117 EValEBB.push_back(i);
118 } else if (Argument *Arg = dyn_cast<Argument>(phiVal)) {
119 // arguments are external
120 if (contains(code, Phi->getIncomingBlock(i)))
121 EValIBB.push_back(i);
123 EValEBB.push_back(i);
126 assert(0 && "Unhandled input in a Phi node");
130 // Both value and block are external. Need to group all of
131 // these, have an external phi, pass the result as an
132 // argument, and have THIS phi use that result.
133 if (EValEBB.size() > 0) {
134 if (EValEBB.size() == 1) {
135 // Now if it's coming from the newFuncRoot, it's that funky input
136 unsigned phiIdx = EValEBB[0];
137 if (!dyn_cast<Constant>(Phi->getIncomingValue(phiIdx)))
139 PhiVal2Arg[Phi].push_back(std::make_pair(phiIdx, inputs.size()));
140 // We can just pass this value in as argument
141 inputs.push_back(Phi->getIncomingValue(phiIdx));
143 Phi->setIncomingBlock(phiIdx, newFuncRoot);
145 PHINode *externalPhi = new PHINode(Phi->getType(), "extPhi");
146 codeReplacer->getInstList().insert(codeReplacer->begin(), externalPhi);
147 for (std::vector<unsigned>::iterator i = EValEBB.begin(),
148 e = EValEBB.end(); i != e; ++i)
150 externalPhi->addIncoming(Phi->getIncomingValue(*i),
151 Phi->getIncomingBlock(*i));
153 // We make these values invalid instead of deleting them because that
154 // would shift the indices of other values... The fixPhiNodes should
155 // clean these phi nodes up later.
156 Phi->setIncomingValue(*i, 0);
157 Phi->setIncomingBlock(*i, 0);
159 PhiVal2Arg[Phi].push_back(std::make_pair(Phi->getNumIncomingValues(),
161 // We can just pass this value in as argument
162 inputs.push_back(externalPhi);
166 // When the value is external, but block internal...
167 // just pass it in as argument, no change to phi node
168 for (std::vector<unsigned>::iterator i = EValIBB.begin(),
169 e = EValIBB.end(); i != e; ++i)
171 // rewrite the phi input node to be an argument
172 PhiVal2Arg[Phi].push_back(std::make_pair(*i, inputs.size()));
173 inputs.push_back(Phi->getIncomingValue(*i));
176 // Value internal, block external
177 // this can happen if we are extracting a part of a loop
178 for (std::vector<unsigned>::iterator i = IValEBB.begin(),
179 e = IValEBB.end(); i != e; ++i)
181 assert(0 && "Cannot (YET) handle internal values via external blocks");
186 void CodeExtractor::findInputsOutputs(const std::vector<BasicBlock*> &code,
189 BasicBlock *newHeader,
190 BasicBlock *newRootNode)
192 for (std::vector<BasicBlock*>::const_iterator ci = code.begin(),
193 ce = code.end(); ci != ce; ++ci) {
194 BasicBlock *BB = *ci;
195 for (BasicBlock::iterator BBi = BB->begin(), BBe = BB->end();
197 // If a use is defined outside the region, it's an input.
198 // If a def is used outside the region, it's an output.
199 if (Instruction *I = dyn_cast<Instruction>(&*BBi)) {
200 // If it's a phi node
201 if (PHINode *Phi = dyn_cast<PHINode>(I)) {
202 processPhiNodeInputs(Phi, code, inputs, newHeader, newRootNode);
204 // All other instructions go through the generic input finder
205 // Loop over the operands of each instruction (inputs)
206 for (User::op_iterator op = I->op_begin(), opE = I->op_end();
208 if (Instruction *opI = dyn_cast<Instruction>(op->get())) {
209 // Check if definition of this operand is within the loop
210 if (!contains(code, opI->getParent())) {
211 // add this operand to the inputs
212 inputs.push_back(opI);
218 // Consider uses of this instruction (outputs)
219 for (Value::use_iterator use = I->use_begin(), useE = I->use_end();
220 use != useE; ++use) {
221 if (Instruction* inst = dyn_cast<Instruction>(*use)) {
222 if (!contains(code, inst->getParent())) {
223 // add this op to the outputs
224 outputs.push_back(I);
230 } /* for: basic blocks */
233 void CodeExtractor::rewritePhiNodes(Function *F,
234 BasicBlock *newFuncRoot) {
235 // Write any changes that were saved before: use function arguments as inputs
236 for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
239 PHINode *phi = (*i).first;
240 PhiValChangesTy &values = (*i).second;
241 for (unsigned cIdx = 0, ce = values.size(); cIdx != ce; ++cIdx)
243 unsigned phiValueIdx = values[cIdx].first, argNum = values[cIdx].second;
244 if (phiValueIdx < phi->getNumIncomingValues())
245 phi->setIncomingValue(phiValueIdx, getFunctionArg(F, argNum));
247 phi->addIncoming(getFunctionArg(F, argNum), newFuncRoot);
251 // Delete any invalid Phi node inputs that were marked as NULL previously
252 for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
255 PHINode *phi = (*i).first;
256 for (unsigned idx = 0, end = phi->getNumIncomingValues(); idx != end; ++idx)
258 if (phi->getIncomingValue(idx) == 0 && phi->getIncomingBlock(idx) == 0) {
259 phi->removeIncomingValue(idx);
266 // We are done with the saved values
271 /// constructFunction - make a function based on inputs and outputs, as follows:
272 /// f(in0, ..., inN, out0, ..., outN)
274 Function *CodeExtractor::constructFunction(const Values &inputs,
275 const Values &outputs,
276 BasicBlock *newRootNode,
277 BasicBlock *newHeader,
278 const std::vector<BasicBlock*> &code,
279 Function *oldFunction, Module *M) {
280 DEBUG(std::cerr << "inputs: " << inputs.size() << "\n");
281 DEBUG(std::cerr << "outputs: " << outputs.size() << "\n");
282 BasicBlock *header = code[0];
284 // This function returns unsigned, outputs will go back by reference.
285 Type *retTy = Type::UShortTy;
286 std::vector<const Type*> paramTy;
288 // Add the types of the input values to the function's argument list
289 for (Values::const_iterator i = inputs.begin(),
290 e = inputs.end(); i != e; ++i) {
291 const Value *value = *i;
292 DEBUG(std::cerr << "value used in func: " << value << "\n");
293 paramTy.push_back(value->getType());
296 // Add the types of the output values to the function's argument list, but
297 // make them pointer types for scalars
298 for (Values::const_iterator i = outputs.begin(),
299 e = outputs.end(); i != e; ++i) {
300 const Value *value = *i;
301 DEBUG(std::cerr << "instr used in func: " << value << "\n");
302 const Type *valueType = value->getType();
303 // Convert scalar types into a pointer of that type
304 if (valueType->isPrimitiveType()) {
305 valueType = PointerType::get(valueType);
307 paramTy.push_back(valueType);
310 DEBUG(std::cerr << "Function type: " << retTy << " f(");
311 for (std::vector<const Type*>::iterator i = paramTy.begin(),
312 e = paramTy.end(); i != e; ++i)
313 DEBUG(std::cerr << (*i) << ", ");
314 DEBUG(std::cerr << ")\n");
316 const FunctionType *funcType = FunctionType::get(retTy, paramTy, false);
318 // Create the new function
319 Function *newFunction = new Function(funcType,
320 GlobalValue::InternalLinkage,
321 oldFunction->getName() + "_code", M);
322 newFunction->getBasicBlockList().push_back(newRootNode);
324 for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
325 std::vector<User*> Users(inputs[i]->use_begin(), inputs[i]->use_end());
326 for (std::vector<User*>::iterator use = Users.begin(), useE = Users.end();
327 use != useE; ++use) {
328 if (Instruction* inst = dyn_cast<Instruction>(*use)) {
329 if (contains(code, inst->getParent())) {
330 inst->replaceUsesOfWith(inputs[i], getFunctionArg(newFunction, i));
336 // Rewrite branches to basic blocks outside of the loop to new dummy blocks
337 // within the new function. This must be done before we lose track of which
338 // blocks were originally in the code region.
339 std::vector<User*> Users(header->use_begin(), header->use_end());
340 for (std::vector<User*>::iterator i = Users.begin(), e = Users.end();
342 if (BranchInst *inst = dyn_cast<BranchInst>(*i)) {
343 BasicBlock *BB = inst->getParent();
344 if (!contains(code, BB) && BB->getParent() == oldFunction) {
345 // The BasicBlock which contains the branch is not in the region
346 // modify the branch target to a new block
347 inst->replaceUsesOfWith(header, newHeader);
355 void CodeExtractor::moveCodeToFunction(const std::vector<BasicBlock*> &code,
356 Function *newFunction)
358 for (std::vector<BasicBlock*>::const_iterator i = code.begin(), e =code.end();
361 Function *oldFunc = BB->getParent();
362 Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList();
364 // Delete the basic block from the old function, and the list of blocks
365 oldBlocks.remove(BB);
367 // Insert this basic block into the new function
368 Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList();
369 newBlocks.push_back(BB);
374 CodeExtractor::emitCallAndSwitchStatement(Function *newFunction,
375 BasicBlock *codeReplacer,
376 const std::vector<BasicBlock*> &code,
380 // Emit a call to the new function, passing allocated memory for outputs and
381 // just plain inputs for non-scalars
382 std::vector<Value*> params;
383 BasicBlock *codeReplacerTail = new BasicBlock("codeReplTail",
384 codeReplacer->getParent());
385 for (Values::const_iterator i = inputs.begin(),
386 e = inputs.end(); i != e; ++i)
387 params.push_back(*i);
388 for (Values::const_iterator i = outputs.begin(),
389 e = outputs.end(); i != e; ++i) {
390 // Create allocas for scalar outputs
391 if ((*i)->getType()->isPrimitiveType()) {
392 Constant *one = ConstantUInt::get(Type::UIntTy, 1);
393 AllocaInst *alloca = new AllocaInst((*i)->getType(), one);
394 codeReplacer->getInstList().push_back(alloca);
395 params.push_back(alloca);
397 LoadInst *load = new LoadInst(alloca, "alloca");
398 codeReplacerTail->getInstList().push_back(load);
399 std::vector<User*> Users((*i)->use_begin(), (*i)->use_end());
400 for (std::vector<User*>::iterator use = Users.begin(), useE =Users.end();
401 use != useE; ++use) {
402 if (Instruction* inst = dyn_cast<Instruction>(*use)) {
403 if (!contains(code, inst->getParent())) {
404 inst->replaceUsesOfWith(*i, load);
409 params.push_back(*i);
412 CallInst *call = new CallInst(newFunction, params, "targetBlock");
413 codeReplacer->getInstList().push_back(call);
414 codeReplacer->getInstList().push_back(new BranchInst(codeReplacerTail));
416 // Now we can emit a switch statement using the call as a value.
417 // FIXME: perhaps instead of default being self BB, it should be a second
418 // dummy block which asserts that the value is not within the range...?
419 //BasicBlock *defaultBlock = new BasicBlock("defaultBlock", oldF);
421 //defaultBlock->getInstList().push_back(new BranchInst(codeReplacer));
423 SwitchInst *switchInst = new SwitchInst(call, codeReplacerTail,
426 // Since there may be multiple exits from the original region, make the new
427 // function return an unsigned, switch on that number
428 unsigned switchVal = 0;
429 for (std::vector<BasicBlock*>::const_iterator i =code.begin(), e = code.end();
433 // rewrite the terminator of the original BasicBlock
434 Instruction *term = BB->getTerminator();
435 if (BranchInst *brInst = dyn_cast<BranchInst>(term)) {
437 // Restore values just before we exit
438 // FIXME: Use a GetElementPtr to bunch the outputs in a struct
439 for (unsigned outIdx = 0, outE = outputs.size(); outIdx != outE; ++outIdx)
441 new StoreInst(outputs[outIdx],
442 getFunctionArg(newFunction, outIdx),
446 // Rewrite branches into exits which return a value based on which
447 // exit we take from this function
448 if (brInst->isUnconditional()) {
449 if (!contains(code, brInst->getSuccessor(0))) {
450 ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal);
451 ReturnInst *newRet = new ReturnInst(brVal);
452 // add a new target to the switch
453 switchInst->addCase(brVal, brInst->getSuccessor(0));
455 // rewrite the branch with a return
456 BasicBlock::iterator ii(brInst);
457 ReplaceInstWithInst(BB->getInstList(), ii, newRet);
461 // Replace the conditional branch to branch
462 // to two new blocks, each of which returns a different code.
463 for (unsigned idx = 0; idx < 2; ++idx) {
464 BasicBlock *oldTarget = brInst->getSuccessor(idx);
465 if (!contains(code, oldTarget)) {
466 // add a new basic block which returns the appropriate value
467 BasicBlock *newTarget = new BasicBlock("newTarget", newFunction);
468 ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal);
469 ReturnInst *newRet = new ReturnInst(brVal);
470 newTarget->getInstList().push_back(newRet);
471 // rewrite the original branch instruction with this new target
472 brInst->setSuccessor(idx, newTarget);
473 // the switch statement knows what to do with this value
474 switchInst->addCase(brVal, oldTarget);
479 } else if (ReturnInst *retTerm = dyn_cast<ReturnInst>(term)) {
480 assert(0 && "Cannot handle return instructions just yet.");
481 // FIXME: what if the terminator is a return!??!
482 // Need to rewrite: add new basic block, move the return there
483 // treat the original as an unconditional branch to that basicblock
484 } else if (SwitchInst *swTerm = dyn_cast<SwitchInst>(term)) {
485 assert(0 && "Cannot handle switch instructions just yet.");
486 } else if (InvokeInst *invInst = dyn_cast<InvokeInst>(term)) {
487 assert(0 && "Cannot handle invoke instructions just yet.");
489 assert(0 && "Unrecognized terminator, or badly-formed BasicBlock.");
495 /// ExtractRegion - Removes a loop from a function, replaces it with a call to
496 /// new function. Returns pointer to the new function.
500 /// find inputs and outputs for the region
502 /// for inputs: add to function as args, map input instr* to arg#
503 /// for outputs: add allocas for scalars,
504 /// add to func as args, map output instr* to arg#
506 /// rewrite func to use argument #s instead of instr*
508 /// for each scalar output in the function: at every exit, store intermediate
509 /// computed result back into memory.
511 Function *CodeExtractor::ExtractCodeRegion(const std::vector<BasicBlock*> &code)
513 // 1) Find inputs, outputs
514 // 2) Construct new function
515 // * Add allocas for defs, pass as args by reference
516 // * Pass in uses as args
517 // 3) Move code region, add call instr to func
520 Values inputs, outputs;
522 // Assumption: this is a single-entry code region, and the header is the first
523 // block in the region. FIXME: is this true for a list of blocks from a
525 BasicBlock *header = code[0];
526 Function *oldFunction = header->getParent();
527 Module *module = oldFunction->getParent();
529 // This takes place of the original loop
530 BasicBlock *codeReplacer = new BasicBlock("codeRepl", oldFunction);
532 // The new function needs a root node because other nodes can branch to the
533 // head of the loop, and the root cannot have predecessors
534 BasicBlock *newFuncRoot = new BasicBlock("newFuncRoot");
535 newFuncRoot->getInstList().push_back(new BranchInst(header));
537 // Find inputs to, outputs from the code region
539 // If one of the inputs is coming from a different basic block and it's in a
540 // phi node, we need to rewrite the phi node:
542 // * All the inputs which involve basic blocks OUTSIDE of this region go into
543 // a NEW phi node that takes care of finding which value really came in.
544 // The result of this phi is passed to the function as an argument.
546 // * All the other phi values stay.
548 // FIXME: PHI nodes' incoming blocks aren't being rewritten to accomodate for
549 // blocks moving to a new function.
550 // SOLUTION: move Phi nodes out of the loop header into the codeReplacer, pass
551 // the values as parameters to the function
552 findInputsOutputs(code, inputs, outputs, codeReplacer, newFuncRoot);
554 // Step 2: Construct new function based on inputs/outputs,
555 // Add allocas for all defs
556 Function *newFunction = constructFunction(inputs, outputs, newFuncRoot,
558 oldFunction, module);
560 rewritePhiNodes(newFunction, newFuncRoot);
562 emitCallAndSwitchStatement(newFunction, codeReplacer, code, inputs, outputs);
564 moveCodeToFunction(code, newFunction);
569 /// ExtractCodeRegion - slurp a sequence of basic blocks into a brand new
572 Function* llvm::ExtractCodeRegion(const std::vector<BasicBlock*> &code) {
574 return CE.ExtractCodeRegion(code);
577 /// ExtractBasicBlock - slurp a natural loop into a brand new function
579 Function* llvm::ExtractLoop(Loop *L) {
581 return CE.ExtractCodeRegion(L->getBlocks());
584 /// ExtractBasicBlock - slurp a basic block into a brand new function
586 Function* llvm::ExtractBasicBlock(BasicBlock *BB) {
588 std::vector<BasicBlock*> Blocks;
589 Blocks.push_back(BB);
590 return CE.ExtractCodeRegion(Blocks);