llvm-6502/lib/Transforms/Utils/CodeExtractor.cpp
Misha Brukman 22108fac63 * Allow aggregating extracted function arguments (controlled by flag)
* Commandline option (for now) controls that flag that is passed in


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13141 91177308-0d34-0410-b5e6-96231b3b80d8
2004-04-23 23:54:17 +00:00

569 lines
23 KiB
C++

//===- CodeExtractor.cpp - Pull code region into a new function -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the interface to tear out a code region, such as an
// individual loop or a parallel section, into a new function, replacing it with
// a call to the new function.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/FunctionUtils.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/Verifier.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "Support/CommandLine.h"
#include "Support/Debug.h"
#include "Support/StringExtras.h"
#include <algorithm>
#include <set>
using namespace llvm;
// Provide a command-line option to aggregate function arguments into a struct
// for functions produced by the code extrator. This is useful when converting
// extracted functions to pthread-based code, as only one argument (void*) can
// be passed in to pthread_create().
static cl::opt<bool>
AggregateArgsOpt("aggregate-extracted-args", cl::Hidden,
cl::desc("Aggregate arguments to code-extracted functions"));
namespace {
class CodeExtractor {
typedef std::vector<Value*> Values;
std::set<BasicBlock*> BlocksToExtract;
DominatorSet *DS;
bool AggregateArgs;
public:
CodeExtractor(DominatorSet *ds = 0, bool AggArgs = false)
: DS(ds), AggregateArgs(AggregateArgsOpt) {}
Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code);
bool isEligible(const std::vector<BasicBlock*> &code);
private:
void findInputsOutputs(Values &inputs, Values &outputs,
BasicBlock *newHeader,
BasicBlock *newRootNode);
Function *constructFunction(const Values &inputs,
const Values &outputs,
BasicBlock *header,
BasicBlock *newRootNode, BasicBlock *newHeader,
Function *oldFunction, Module *M);
void moveCodeToFunction(Function *newFunction);
void emitCallAndSwitchStatement(Function *newFunction,
BasicBlock *newHeader,
Values &inputs,
Values &outputs);
};
}
void CodeExtractor::findInputsOutputs(Values &inputs, Values &outputs,
BasicBlock *newHeader,
BasicBlock *newRootNode) {
for (std::set<BasicBlock*>::const_iterator ci = BlocksToExtract.begin(),
ce = BlocksToExtract.end(); ci != ce; ++ci) {
BasicBlock *BB = *ci;
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
// If a used value is defined outside the region, it's an input. If an
// instruction is used outside the region, it's an output.
if (PHINode *PN = dyn_cast<PHINode>(I)) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Value *V = PN->getIncomingValue(i);
if (!BlocksToExtract.count(PN->getIncomingBlock(i)) &&
(isa<Instruction>(V) || isa<Argument>(V)))
inputs.push_back(V);
else if (Instruction *opI = dyn_cast<Instruction>(V)) {
if (!BlocksToExtract.count(opI->getParent()))
inputs.push_back(opI);
} else if (isa<Argument>(V))
inputs.push_back(V);
}
} else {
// All other instructions go through the generic input finder
// Loop over the operands of each instruction (inputs)
for (User::op_iterator op = I->op_begin(), opE = I->op_end();
op != opE; ++op)
if (Instruction *opI = dyn_cast<Instruction>(*op)) {
// Check if definition of this operand is within the loop
if (!BlocksToExtract.count(opI->getParent()))
inputs.push_back(opI);
} else if (isa<Argument>(*op)) {
inputs.push_back(*op);
}
}
// Consider uses of this instruction (outputs)
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI)
if (!BlocksToExtract.count(cast<Instruction>(*UI)->getParent())) {
outputs.push_back(I);
break;
}
} // for: insts
} // for: basic blocks
}
/// constructFunction - make a function based on inputs and outputs, as follows:
/// f(in0, ..., inN, out0, ..., outN)
///
Function *CodeExtractor::constructFunction(const Values &inputs,
const Values &outputs,
BasicBlock *header,
BasicBlock *newRootNode,
BasicBlock *newHeader,
Function *oldFunction,
Module *M) {
DEBUG(std::cerr << "inputs: " << inputs.size() << "\n");
DEBUG(std::cerr << "outputs: " << outputs.size() << "\n");
// This function returns unsigned, outputs will go back by reference.
Type *retTy = Type::UShortTy;
std::vector<const Type*> paramTy;
// Add the types of the input values to the function's argument list
for (Values::const_iterator i = inputs.begin(),
e = inputs.end(); i != e; ++i) {
const Value *value = *i;
DEBUG(std::cerr << "value used in func: " << value << "\n");
paramTy.push_back(value->getType());
}
// Add the types of the output values to the function's argument list.
for (Values::const_iterator I = outputs.begin(), E = outputs.end();
I != E; ++I) {
DEBUG(std::cerr << "instr used in func: " << *I << "\n");
if (AggregateArgs)
paramTy.push_back((*I)->getType());
else
paramTy.push_back(PointerType::get((*I)->getType()));
}
DEBUG(std::cerr << "Function type: " << retTy << " f(");
DEBUG(for (std::vector<const Type*>::iterator i = paramTy.begin(),
e = paramTy.end(); i != e; ++i) std::cerr << *i << ", ");
DEBUG(std::cerr << ")\n");
if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
PointerType *StructPtr = PointerType::get(StructType::get(paramTy));
paramTy.clear();
paramTy.push_back(StructPtr);
}
const FunctionType *funcType = FunctionType::get(retTy, paramTy, false);
// Create the new function
Function *newFunction = new Function(funcType,
GlobalValue::InternalLinkage,
oldFunction->getName() + "_code", M);
newFunction->getBasicBlockList().push_back(newRootNode);
// Create an iterator to name all of the arguments we inserted.
Function::aiterator AI = newFunction->abegin();
// Rewrite all users of the inputs in the extracted region to use the
// arguments (or appropriate addressing into struct) instead.
for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
Value *RewriteVal;
if (AggregateArgs) {
std::vector<Value*> Indices;
Indices.push_back(Constant::getNullValue(Type::UIntTy));
Indices.push_back(ConstantUInt::get(Type::UIntTy, i));
std::string GEPname = "gep_" + inputs[i]->getName();
TerminatorInst *TI = newFunction->begin()->getTerminator();
GetElementPtrInst *GEP = new GetElementPtrInst(AI, Indices, GEPname, TI);
RewriteVal = new LoadInst(GEP, "load" + GEPname, TI);
} else
RewriteVal = AI++;
std::vector<User*> Users(inputs[i]->use_begin(), inputs[i]->use_end());
for (std::vector<User*>::iterator use = Users.begin(), useE = Users.end();
use != useE; ++use)
if (Instruction* inst = dyn_cast<Instruction>(*use))
if (BlocksToExtract.count(inst->getParent()))
inst->replaceUsesOfWith(inputs[i], RewriteVal);
}
// Set names for input and output arguments.
if (!AggregateArgs) {
AI = newFunction->abegin();
for (unsigned i = 0, e = inputs.size(); i != e; ++i, ++AI)
AI->setName(inputs[i]->getName());
for (unsigned i = 0, e = outputs.size(); i != e; ++i, ++AI)
AI->setName(outputs[i]->getName()+".out");
}
// Rewrite branches to basic blocks outside of the loop to new dummy blocks
// within the new function. This must be done before we lose track of which
// blocks were originally in the code region.
std::vector<User*> Users(header->use_begin(), header->use_end());
for (unsigned i = 0, e = Users.size(); i != e; ++i)
// The BasicBlock which contains the branch is not in the region
// modify the branch target to a new block
if (TerminatorInst *TI = dyn_cast<TerminatorInst>(Users[i]))
if (!BlocksToExtract.count(TI->getParent()) &&
TI->getParent()->getParent() == oldFunction)
TI->replaceUsesOfWith(header, newHeader);
return newFunction;
}
void CodeExtractor::moveCodeToFunction(Function *newFunction) {
Function *oldFunc = (*BlocksToExtract.begin())->getParent();
Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList();
Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList();
for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
e = BlocksToExtract.end(); i != e; ++i) {
// Delete the basic block from the old function, and the list of blocks
oldBlocks.remove(*i);
// Insert this basic block into the new function
newBlocks.push_back(*i);
}
}
void
CodeExtractor::emitCallAndSwitchStatement(Function *newFunction,
BasicBlock *codeReplacer,
Values &inputs,
Values &outputs) {
// Emit a call to the new function, passing in:
// *pointer to struct (if aggregating parameters), or
// plan inputs and allocated memory for outputs
std::vector<Value*> params, StructValues, ReloadOutputs;
// Add inputs as params, or to be filled into the struct
for (Values::iterator i = inputs.begin(), e = inputs.end(); i != e; ++i)
if (AggregateArgs)
StructValues.push_back(*i);
else
params.push_back(*i);
// Create allocas for the outputs
for (Values::iterator i = outputs.begin(), e = outputs.end(); i != e; ++i) {
if (AggregateArgs) {
StructValues.push_back(*i);
} else {
AllocaInst *alloca =
new AllocaInst((*i)->getType(), 0, (*i)->getName()+".loc",
codeReplacer->getParent()->begin()->begin());
ReloadOutputs.push_back(alloca);
params.push_back(alloca);
}
}
AllocaInst *Struct = 0;
if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
std::vector<const Type*> ArgTypes;
for (Values::iterator v = StructValues.begin(),
ve = StructValues.end(); v != ve; ++v)
ArgTypes.push_back((*v)->getType());
// Allocate a struct at the beginning of this function
Type *StructArgTy = StructType::get(ArgTypes);
Struct =
new AllocaInst(StructArgTy, 0, "structArg",
codeReplacer->getParent()->begin()->begin());
params.push_back(Struct);
for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
std::vector<Value*> Indices;
Indices.push_back(Constant::getNullValue(Type::UIntTy));
Indices.push_back(ConstantUInt::get(Type::UIntTy, i));
GetElementPtrInst *GEP =
new GetElementPtrInst(Struct, Indices,
"gep_" + StructValues[i]->getName(), 0);
codeReplacer->getInstList().push_back(GEP);
StoreInst *SI = new StoreInst(StructValues[i], GEP);
codeReplacer->getInstList().push_back(SI);
}
}
// Emit the call to the function
CallInst *call = new CallInst(newFunction, params, "targetBlock");
codeReplacer->getInstList().push_back(call);
Function::aiterator OutputArgBegin = newFunction->abegin();
unsigned FirstOut = inputs.size();
if (!AggregateArgs)
std::advance(OutputArgBegin, inputs.size());
// Reload the outputs passed in by reference
for (unsigned i = 0, e = outputs.size(); i != e; ++i) {
Value *Output = 0;
if (AggregateArgs) {
std::vector<Value*> Indices;
Indices.push_back(Constant::getNullValue(Type::UIntTy));
Indices.push_back(ConstantUInt::get(Type::UIntTy, FirstOut + i));
GetElementPtrInst *GEP
= new GetElementPtrInst(Struct, Indices,
"gep_reload_" + outputs[i]->getName(), 0);
codeReplacer->getInstList().push_back(GEP);
Output = GEP;
} else {
Output = ReloadOutputs[i];
}
LoadInst *load = new LoadInst(Output, outputs[i]->getName()+".reload");
codeReplacer->getInstList().push_back(load);
std::vector<User*> Users(outputs[i]->use_begin(), outputs[i]->use_end());
for (unsigned u = 0, e = Users.size(); u != e; ++u) {
Instruction *inst = cast<Instruction>(Users[u]);
if (!BlocksToExtract.count(inst->getParent()))
inst->replaceUsesOfWith(outputs[i], load);
}
}
// Now we can emit a switch statement using the call as a value.
SwitchInst *TheSwitch = new SwitchInst(call, codeReplacer, codeReplacer);
// Since there may be multiple exits from the original region, make the new
// function return an unsigned, switch on that number. This loop iterates
// over all of the blocks in the extracted region, updating any terminator
// instructions in the to-be-extracted region that branch to blocks that are
// not in the region to be extracted.
std::map<BasicBlock*, BasicBlock*> ExitBlockMap;
unsigned switchVal = 0;
for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
e = BlocksToExtract.end(); i != e; ++i) {
TerminatorInst *TI = (*i)->getTerminator();
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
if (!BlocksToExtract.count(TI->getSuccessor(i))) {
BasicBlock *OldTarget = TI->getSuccessor(i);
// add a new basic block which returns the appropriate value
BasicBlock *&NewTarget = ExitBlockMap[OldTarget];
if (!NewTarget) {
// If we don't already have an exit stub for this non-extracted
// destination, create one now!
NewTarget = new BasicBlock(OldTarget->getName() + ".exitStub",
newFunction);
ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal++);
ReturnInst *NTRet = new ReturnInst(brVal, NewTarget);
// Update the switch instruction.
TheSwitch->addCase(brVal, OldTarget);
// Restore values just before we exit
Function::aiterator OAI = OutputArgBegin;
for (unsigned out = 0, e = outputs.size(); out != e; ++out) {
// For an invoke, the normal destination is the only one that is
// dominated by the result of the invocation
BasicBlock *DefBlock = cast<Instruction>(outputs[out])->getParent();
if (InvokeInst *Invoke = dyn_cast<InvokeInst>(outputs[out]))
DefBlock = Invoke->getNormalDest();
if (!DS || DS->dominates(DefBlock, TI->getParent()))
if (AggregateArgs) {
std::vector<Value*> Indices;
Indices.push_back(Constant::getNullValue(Type::UIntTy));
Indices.push_back(ConstantUInt::get(Type::UIntTy,FirstOut+out));
GetElementPtrInst *GEP =
new GetElementPtrInst(OAI, Indices,
"gep_" + outputs[out]->getName(),
NTRet);
new StoreInst(outputs[out], GEP, NTRet);
} else
new StoreInst(outputs[out], OAI, NTRet);
// Advance output iterator even if we don't emit a store
if (!AggregateArgs) ++OAI;
}
}
// rewrite the original branch instruction with this new target
TI->setSuccessor(i, NewTarget);
}
}
// Now that we've done the deed, make the default destination of the switch
// instruction be a block with a call to abort() -- since this path should not
// be taken, this will abort sooner rather than later.
if (TheSwitch->getNumSuccessors() > 1) {
Function *container = codeReplacer->getParent();
BasicBlock *abortBB = new BasicBlock("abortBlock", container);
std::vector<const Type*> paramTypes;
FunctionType *abortTy = FunctionType::get(Type::VoidTy, paramTypes, false);
Function *abortFunc =
container->getParent()->getOrInsertFunction("abort", abortTy);
abortBB->getInstList().push_back(new CallInst(abortFunc));
Function *ParentFunc = TheSwitch->getParent()->getParent();
if (ParentFunc->getReturnType() == Type::VoidTy)
new ReturnInst(0, abortBB);
else
new ReturnInst(Constant::getNullValue(ParentFunc->getReturnType()),
abortBB);
TheSwitch->setSuccessor(0, abortBB);
} else {
// There is only 1 successor (the block containing the switch itself), which
// means that previously this was the last part of the function, and hence
// this should be rewritten as a `ret'
// Check if the function should return a value
if (TheSwitch->getParent()->getParent()->getReturnType() != Type::VoidTy &&
TheSwitch->getParent()->getParent()->getReturnType() ==
TheSwitch->getCondition()->getType())
// return what we have
new ReturnInst(TheSwitch->getCondition(), TheSwitch);
else
// just return
new ReturnInst(0, TheSwitch);
TheSwitch->getParent()->getInstList().erase(TheSwitch);
}
}
/// ExtractRegion - Removes a loop from a function, replaces it with a call to
/// new function. Returns pointer to the new function.
///
/// algorithm:
///
/// find inputs and outputs for the region
///
/// for inputs: add to function as args, map input instr* to arg#
/// for outputs: add allocas for scalars,
/// add to func as args, map output instr* to arg#
///
/// rewrite func to use argument #s instead of instr*
///
/// for each scalar output in the function: at every exit, store intermediate
/// computed result back into memory.
///
Function *CodeExtractor::ExtractCodeRegion(const std::vector<BasicBlock*> &code)
{
if (!isEligible(code))
return 0;
// 1) Find inputs, outputs
// 2) Construct new function
// * Add allocas for defs, pass as args by reference
// * Pass in uses as args
// 3) Move code region, add call instr to func
//
BlocksToExtract.insert(code.begin(), code.end());
Values inputs, outputs;
// Assumption: this is a single-entry code region, and the header is the first
// block in the region.
BasicBlock *header = code[0];
for (unsigned i = 1, e = code.size(); i != e; ++i)
for (pred_iterator PI = pred_begin(code[i]), E = pred_end(code[i]);
PI != E; ++PI)
assert(BlocksToExtract.count(*PI) &&
"No blocks in this region may have entries from outside the region"
" except for the first block!");
Function *oldFunction = header->getParent();
// This takes place of the original loop
BasicBlock *codeReplacer = new BasicBlock("codeRepl", oldFunction);
// The new function needs a root node because other nodes can branch to the
// head of the loop, and the root cannot have predecessors
BasicBlock *newFuncRoot = new BasicBlock("newFuncRoot");
newFuncRoot->getInstList().push_back(new BranchInst(header));
// Find inputs to, outputs from the code region
//
// If one of the inputs is coming from a different basic block and it's in a
// phi node, we need to rewrite the phi node:
//
// * All the inputs which involve basic blocks OUTSIDE of this region go into
// a NEW phi node that takes care of finding which value really came in.
// The result of this phi is passed to the function as an argument.
//
// * All the other phi values stay.
//
// FIXME: PHI nodes' incoming blocks aren't being rewritten to accomodate for
// blocks moving to a new function.
// SOLUTION: move Phi nodes out of the loop header into the codeReplacer, pass
// the values as parameters to the function
findInputsOutputs(inputs, outputs, codeReplacer, newFuncRoot);
// Step 2: Construct new function based on inputs/outputs,
// Add allocas for all defs
Function *newFunction = constructFunction(inputs, outputs, code[0],
newFuncRoot,
codeReplacer, oldFunction,
oldFunction->getParent());
emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);
moveCodeToFunction(newFunction);
// Loop over all of the PHI nodes in the entry block (code[0]), and change any
// references to the old incoming edge to be the new incoming edge.
for (BasicBlock::iterator I = code[0]->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I)
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (!BlocksToExtract.count(PN->getIncomingBlock(i)))
PN->setIncomingBlock(i, newFuncRoot);
// Look at all successors of the codeReplacer block. If any of these blocks
// had PHI nodes in them, we need to update the "from" block to be the code
// replacer, not the original block in the extracted region.
std::vector<BasicBlock*> Succs(succ_begin(codeReplacer),
succ_end(codeReplacer));
for (unsigned i = 0, e = Succs.size(); i != e; ++i)
for (BasicBlock::iterator I = Succs[i]->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I)
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (BlocksToExtract.count(PN->getIncomingBlock(i)))
PN->setIncomingBlock(i, codeReplacer);
DEBUG(if (verifyFunction(*newFunction)) abort());
return newFunction;
}
bool CodeExtractor::isEligible(const std::vector<BasicBlock*> &code) {
// Deny code region if it contains allocas
for (std::vector<BasicBlock*>::const_iterator BB = code.begin(), e=code.end();
BB != e; ++BB)
for (BasicBlock::const_iterator I = (*BB)->begin(), Ie = (*BB)->end();
I != Ie; ++I)
if (isa<AllocaInst>(*I))
return false;
return true;
}
/// ExtractCodeRegion - slurp a sequence of basic blocks into a brand new
/// function
///
Function* llvm::ExtractCodeRegion(DominatorSet &DS,
const std::vector<BasicBlock*> &code,
bool AggregateArgs) {
return CodeExtractor(&DS, AggregateArgs).ExtractCodeRegion(code);
}
/// ExtractBasicBlock - slurp a natural loop into a brand new function
///
Function* llvm::ExtractLoop(DominatorSet &DS, Loop *L, bool AggregateArgs) {
return CodeExtractor(&DS, AggregateArgs).ExtractCodeRegion(L->getBlocks());
}
/// ExtractBasicBlock - slurp a basic block into a brand new function
///
Function* llvm::ExtractBasicBlock(BasicBlock *BB, bool AggregateArgs) {
std::vector<BasicBlock*> Blocks;
Blocks.push_back(BB);
return CodeExtractor(0, AggregateArgs).ExtractCodeRegion(Blocks);
}