llvm-6502/lib/Transforms/IPO/LoopExtractor.cpp
Paul Robinson 2684ddd72e Disable most IR-level transform passes on functions marked 'optnone'.
Ideally only those transform passes that run at -O0 remain enabled,
in reality we get as close as we reasonably can.
Passes are responsible for disabling themselves, it's not the job of
the pass manager to do it for them.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200892 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-06 00:07:05 +00:00

308 lines
10 KiB
C++

//===- LoopExtractor.cpp - Extract each loop into a new function ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// A pass wrapper around the ExtractLoop() scalar transformation to extract each
// top-level loop into its own new function. If the loop is the ONLY loop in a
// given function, it is not touched. This is a pass most useful for debugging
// via bugpoint.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "loop-extract"
#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/CodeExtractor.h"
#include <fstream>
#include <set>
using namespace llvm;
STATISTIC(NumExtracted, "Number of loops extracted");
namespace {
struct LoopExtractor : public LoopPass {
static char ID; // Pass identification, replacement for typeid
unsigned NumLoops;
explicit LoopExtractor(unsigned numLoops = ~0)
: LoopPass(ID), NumLoops(numLoops) {
initializeLoopExtractorPass(*PassRegistry::getPassRegistry());
}
virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequiredID(BreakCriticalEdgesID);
AU.addRequiredID(LoopSimplifyID);
AU.addRequired<DominatorTreeWrapperPass>();
}
};
}
char LoopExtractor::ID = 0;
INITIALIZE_PASS_BEGIN(LoopExtractor, "loop-extract",
"Extract loops into new functions", false, false)
INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges)
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(LoopExtractor, "loop-extract",
"Extract loops into new functions", false, false)
namespace {
/// SingleLoopExtractor - For bugpoint.
struct SingleLoopExtractor : public LoopExtractor {
static char ID; // Pass identification, replacement for typeid
SingleLoopExtractor() : LoopExtractor(1) {}
};
} // End anonymous namespace
char SingleLoopExtractor::ID = 0;
INITIALIZE_PASS(SingleLoopExtractor, "loop-extract-single",
"Extract at most one loop into a new function", false, false)
// createLoopExtractorPass - This pass extracts all natural loops from the
// program into a function if it can.
//
Pass *llvm::createLoopExtractorPass() { return new LoopExtractor(); }
bool LoopExtractor::runOnLoop(Loop *L, LPPassManager &LPM) {
if (skipOptnoneFunction(L))
return false;
// Only visit top-level loops.
if (L->getParentLoop())
return false;
// If LoopSimplify form is not available, stay out of trouble.
if (!L->isLoopSimplifyForm())
return false;
DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
bool Changed = false;
// If there is more than one top-level loop in this function, extract all of
// the loops. Otherwise there is exactly one top-level loop; in this case if
// this function is more than a minimal wrapper around the loop, extract
// the loop.
bool ShouldExtractLoop = false;
// Extract the loop if the entry block doesn't branch to the loop header.
TerminatorInst *EntryTI =
L->getHeader()->getParent()->getEntryBlock().getTerminator();
if (!isa<BranchInst>(EntryTI) ||
!cast<BranchInst>(EntryTI)->isUnconditional() ||
EntryTI->getSuccessor(0) != L->getHeader()) {
ShouldExtractLoop = true;
} else {
// Check to see if any exits from the loop are more than just return
// blocks.
SmallVector<BasicBlock*, 8> ExitBlocks;
L->getExitBlocks(ExitBlocks);
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
if (!isa<ReturnInst>(ExitBlocks[i]->getTerminator())) {
ShouldExtractLoop = true;
break;
}
}
if (ShouldExtractLoop) {
// We must omit landing pads. Landing pads must accompany the invoke
// instruction. But this would result in a loop in the extracted
// function. An infinite cycle occurs when it tries to extract that loop as
// well.
SmallVector<BasicBlock*, 8> ExitBlocks;
L->getExitBlocks(ExitBlocks);
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
if (ExitBlocks[i]->isLandingPad()) {
ShouldExtractLoop = false;
break;
}
}
if (ShouldExtractLoop) {
if (NumLoops == 0) return Changed;
--NumLoops;
CodeExtractor Extractor(DT, *L);
if (Extractor.extractCodeRegion() != 0) {
Changed = true;
// After extraction, the loop is replaced by a function call, so
// we shouldn't try to run any more loop passes on it.
LPM.deleteLoopFromQueue(L);
}
++NumExtracted;
}
return Changed;
}
// createSingleLoopExtractorPass - This pass extracts one natural loop from the
// program into a function if it can. This is used by bugpoint.
//
Pass *llvm::createSingleLoopExtractorPass() {
return new SingleLoopExtractor();
}
// BlockFile - A file which contains a list of blocks that should not be
// extracted.
static cl::opt<std::string>
BlockFile("extract-blocks-file", cl::value_desc("filename"),
cl::desc("A file containing list of basic blocks to not extract"),
cl::Hidden);
namespace {
/// BlockExtractorPass - This pass is used by bugpoint to extract all blocks
/// from the module into their own functions except for those specified by the
/// BlocksToNotExtract list.
class BlockExtractorPass : public ModulePass {
void LoadFile(const char *Filename);
void SplitLandingPadPreds(Function *F);
std::vector<BasicBlock*> BlocksToNotExtract;
std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName;
public:
static char ID; // Pass identification, replacement for typeid
BlockExtractorPass() : ModulePass(ID) {
if (!BlockFile.empty())
LoadFile(BlockFile.c_str());
}
bool runOnModule(Module &M);
};
}
char BlockExtractorPass::ID = 0;
INITIALIZE_PASS(BlockExtractorPass, "extract-blocks",
"Extract Basic Blocks From Module (for bugpoint use)",
false, false)
// createBlockExtractorPass - This pass extracts all blocks (except those
// specified in the argument list) from the functions in the module.
//
ModulePass *llvm::createBlockExtractorPass() {
return new BlockExtractorPass();
}
void BlockExtractorPass::LoadFile(const char *Filename) {
// Load the BlockFile...
std::ifstream In(Filename);
if (!In.good()) {
errs() << "WARNING: BlockExtractor couldn't load file '" << Filename
<< "'!\n";
return;
}
while (In) {
std::string FunctionName, BlockName;
In >> FunctionName;
In >> BlockName;
if (!BlockName.empty())
BlocksToNotExtractByName.push_back(
std::make_pair(FunctionName, BlockName));
}
}
/// SplitLandingPadPreds - The landing pad needs to be extracted with the invoke
/// instruction. The critical edge breaker will refuse to break critical edges
/// to a landing pad. So do them here. After this method runs, all landing pads
/// should have only one predecessor.
void BlockExtractorPass::SplitLandingPadPreds(Function *F) {
for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
InvokeInst *II = dyn_cast<InvokeInst>(I);
if (!II) continue;
BasicBlock *Parent = II->getParent();
BasicBlock *LPad = II->getUnwindDest();
// Look through the landing pad's predecessors. If one of them ends in an
// 'invoke', then we want to split the landing pad.
bool Split = false;
for (pred_iterator
PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ++PI) {
BasicBlock *BB = *PI;
if (BB->isLandingPad() && BB != Parent &&
isa<InvokeInst>(Parent->getTerminator())) {
Split = true;
break;
}
}
if (!Split) continue;
SmallVector<BasicBlock*, 2> NewBBs;
SplitLandingPadPredecessors(LPad, Parent, ".1", ".2", 0, NewBBs);
}
}
bool BlockExtractorPass::runOnModule(Module &M) {
std::set<BasicBlock*> TranslatedBlocksToNotExtract;
for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) {
BasicBlock *BB = BlocksToNotExtract[i];
Function *F = BB->getParent();
// Map the corresponding function in this module.
Function *MF = M.getFunction(F->getName());
assert(MF->getFunctionType() == F->getFunctionType() && "Wrong function?");
// Figure out which index the basic block is in its function.
Function::iterator BBI = MF->begin();
std::advance(BBI, std::distance(F->begin(), Function::iterator(BB)));
TranslatedBlocksToNotExtract.insert(BBI);
}
while (!BlocksToNotExtractByName.empty()) {
// There's no way to find BBs by name without looking at every BB inside
// every Function. Fortunately, this is always empty except when used by
// bugpoint in which case correctness is more important than performance.
std::string &FuncName = BlocksToNotExtractByName.back().first;
std::string &BlockName = BlocksToNotExtractByName.back().second;
for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
Function &F = *FI;
if (F.getName() != FuncName) continue;
for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
BasicBlock &BB = *BI;
if (BB.getName() != BlockName) continue;
TranslatedBlocksToNotExtract.insert(BI);
}
}
BlocksToNotExtractByName.pop_back();
}
// Now that we know which blocks to not extract, figure out which ones we WANT
// to extract.
std::vector<BasicBlock*> BlocksToExtract;
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
SplitLandingPadPreds(&*F);
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
if (!TranslatedBlocksToNotExtract.count(BB))
BlocksToExtract.push_back(BB);
}
for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i) {
SmallVector<BasicBlock*, 2> BlocksToExtractVec;
BlocksToExtractVec.push_back(BlocksToExtract[i]);
if (const InvokeInst *II =
dyn_cast<InvokeInst>(BlocksToExtract[i]->getTerminator()))
BlocksToExtractVec.push_back(II->getUnwindDest());
CodeExtractor(BlocksToExtractVec).extractCodeRegion();
}
return !BlocksToExtract.empty();
}