llvm-6502/lib/Analysis/RegionInfo.cpp
2010-08-10 09:54:35 +00:00

750 lines
20 KiB
C++

//===- RegionInfo.cpp - SESE region detection analysis --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// Detects single entry single exit regions in the control flow graph.
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/RegionInfo.h"
#include "llvm/Analysis/RegionIterator.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Analysis/LoopInfo.h"
#define DEBUG_TYPE "region"
#include "llvm/Support/Debug.h"
#include <set>
#include <algorithm>
using namespace llvm;
// Always verify if expensive checking is enabled.
#ifdef XDEBUG
static bool VerifyRegionInfo = true;
#else
static bool VerifyRegionInfo = false;
#endif
static cl::opt<bool,true>
VerifyRegionInfoX("verify-region-info", cl::location(VerifyRegionInfo),
cl::desc("Verify region info (time consuming)"));
STATISTIC(numRegions, "The # of regions");
STATISTIC(numSimpleRegions, "The # of simple regions");
//===----------------------------------------------------------------------===//
/// PrintStyle - Print region in difference ways.
enum PrintStyle { PrintNone, PrintBB, PrintRN };
cl::opt<enum PrintStyle> printStyle("print-region-style", cl::Hidden,
cl::desc("style of printing regions"),
cl::values(
clEnumValN(PrintNone, "none", "print no details"),
clEnumValN(PrintBB, "bb", "print regions in detail with block_iterator"),
clEnumValN(PrintRN, "rn", "print regions in detail with element_iterator"),
clEnumValEnd));
//===----------------------------------------------------------------------===//
/// Region Implementation
Region::Region(BasicBlock *Entry, BasicBlock *Exit, RegionInfo* RInfo,
DominatorTree *dt, Region *Parent)
: RegionNode(Parent, Entry, 1), RI(RInfo), DT(dt), exit(Exit) {}
Region::~Region() {
// Free the cached nodes.
for (BBNodeMapT::iterator it = BBNodeMap.begin(),
ie = BBNodeMap.end(); it != ie; ++it)
delete it->second;
// Only clean the cache for this Region. Caches of child Regions will be
// cleaned when the child Regions are deleted.
BBNodeMap.clear();
for (iterator I = begin(), E = end(); I != E; ++I)
delete *I;
}
bool Region::contains(const BasicBlock *B) const {
BasicBlock *BB = const_cast<BasicBlock*>(B);
assert(DT->getNode(BB) && "BB not part of the dominance tree");
BasicBlock *entry = getEntry(), *exit = getExit();
// Toplevel region.
if (!exit)
return true;
return (DT->dominates(entry, BB)
&& !(DT->dominates(exit, BB) && DT->dominates(entry, exit)));
}
bool Region::contains(const Loop *L) const {
// BBs that are not part of any loop are element of the Loop
// described by the NULL pointer. This loop is not part of any region,
// except if the region describes the whole function.
if (L == 0)
return getExit() == 0;
if (!contains(L->getHeader()))
return false;
SmallVector<BasicBlock *, 8> ExitingBlocks;
L->getExitingBlocks(ExitingBlocks);
for (SmallVectorImpl<BasicBlock*>::iterator BI = ExitingBlocks.begin(),
BE = ExitingBlocks.end(); BI != BE; ++BI)
if (!contains(*BI))
return false;
return true;
}
Loop *Region::outermostLoopInRegion(Loop *L) const {
if (!contains(L))
return 0;
while (L && contains(L->getParentLoop())) {
L = L->getParentLoop();
}
return L;
}
Loop *Region::outermostLoopInRegion(LoopInfo *LI, BasicBlock* BB) const {
assert(LI && BB && "LI and BB cannot be null!");
Loop *L = LI->getLoopFor(BB);
return outermostLoopInRegion(L);
}
bool Region::isSimple() const {
bool isSimple = true;
bool found = false;
BasicBlock *entry = getEntry(), *exit = getExit();
// TopLevelRegion
if (!exit)
return false;
for (pred_iterator PI = pred_begin(entry), PE = pred_end(entry); PI != PE;
++PI) {
BasicBlock *Pred = *PI;
if (DT->getNode(Pred) && !contains(Pred)) {
if (found) {
isSimple = false;
break;
}
found = true;
}
}
found = false;
for (pred_iterator PI = pred_begin(exit), PE = pred_end(exit); PI != PE;
++PI)
if (contains(*PI)) {
if (found) {
isSimple = false;
break;
}
found = true;
}
return isSimple;
}
std::string Region::getNameStr() const {
std::string exitName;
std::string entryName;
if (getEntry()->getName().empty()) {
raw_string_ostream OS(entryName);
WriteAsOperand(OS, getEntry(), false);
entryName = OS.str();
} else
entryName = getEntry()->getNameStr();
if (getExit()) {
if (getExit()->getName().empty()) {
raw_string_ostream OS(exitName);
WriteAsOperand(OS, getExit(), false);
exitName = OS.str();
} else
exitName = getExit()->getNameStr();
} else
exitName = "<Function Return>";
return entryName + " => " + exitName;
}
void Region::verifyBBInRegion(BasicBlock *BB) const {
if (!contains(BB))
llvm_unreachable("Broken region found!");
BasicBlock *entry = getEntry(), *exit = getExit();
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
if (!contains(*SI) && exit != *SI)
llvm_unreachable("Broken region found!");
if (entry != BB)
for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB); SI != SE; ++SI)
if (!contains(*SI))
llvm_unreachable("Broken region found!");
}
void Region::verifyWalk(BasicBlock *BB, std::set<BasicBlock*> *visited) const {
BasicBlock *exit = getExit();
visited->insert(BB);
verifyBBInRegion(BB);
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
if (*SI != exit && visited->find(*SI) == visited->end())
verifyWalk(*SI, visited);
}
void Region::verifyRegion() const {
// Only do verification when user wants to, otherwise this expensive
// check will be invoked by PassManager.
if (!VerifyRegionInfo) return;
std::set<BasicBlock*> visited;
verifyWalk(getEntry(), &visited);
}
void Region::verifyRegionNest() const {
for (Region::const_iterator RI = begin(), RE = end(); RI != RE; ++RI)
(*RI)->verifyRegionNest();
verifyRegion();
}
Region::block_iterator Region::block_begin() {
return GraphTraits<FlatIt<Region*> >::nodes_begin(this);
}
Region::block_iterator Region::block_end() {
return GraphTraits<FlatIt<Region*> >::nodes_end(this);
}
Region::const_block_iterator Region::block_begin() const {
return GraphTraits<FlatIt<const Region*> >::nodes_begin(this);
}
Region::const_block_iterator Region::block_end() const {
return GraphTraits<FlatIt<const Region*> >::nodes_end(this);
}
Region::element_iterator Region::element_begin() {
return GraphTraits<Region*>::nodes_begin(this);
}
Region::element_iterator Region::element_end() {
return GraphTraits<Region*>::nodes_end(this);
}
Region::const_element_iterator Region::element_begin() const {
return GraphTraits<const Region*>::nodes_begin(this);
}
Region::const_element_iterator Region::element_end() const {
return GraphTraits<const Region*>::nodes_end(this);
}
Region* Region::getSubRegionNode(BasicBlock *BB) const {
Region *R = RI->getRegionFor(BB);
if (!R || R == this)
return 0;
// If we pass the BB out of this region, that means our code is broken.
assert(contains(R) && "BB not in current region!");
while (contains(R->getParent()) && R->getParent() != this)
R = R->getParent();
if (R->getEntry() != BB)
return 0;
return R;
}
RegionNode* Region::getBBNode(BasicBlock *BB) const {
assert(contains(BB) && "Can get BB node out of this region!");
BBNodeMapT::const_iterator at = BBNodeMap.find(BB);
if (at != BBNodeMap.end())
return at->second;
RegionNode *NewNode = new RegionNode(const_cast<Region*>(this), BB);
BBNodeMap.insert(std::make_pair(BB, NewNode));
return NewNode;
}
RegionNode* Region::getNode(BasicBlock *BB) const {
assert(contains(BB) && "Can get BB node out of this region!");
if (Region* Child = getSubRegionNode(BB))
return Child->getNode();
return getBBNode(BB);
}
void Region::transferChildrenTo(Region *To) {
for (iterator I = begin(), E = end(); I != E; ++I) {
(*I)->parent = To;
To->children.push_back(*I);
}
children.clear();
}
void Region::addSubRegion(Region *SubRegion) {
assert(SubRegion->parent == 0 && "SubRegion already has a parent!");
SubRegion->parent = this;
// Set up the region node.
assert(std::find(children.begin(), children.end(), SubRegion) == children.end()
&& "Node already exist!");
children.push_back(SubRegion);
}
Region *Region::removeSubRegion(Region *Child) {
assert(Child->parent == this && "Child is not a child of this region!");
Child->parent = 0;
RegionSet::iterator I = std::find(children.begin(), children.end(), Child);
assert(I != children.end() && "Region does not exit. Unable to remove.");
children.erase(children.begin()+(I-begin()));
return Child;
}
unsigned Region::getDepth() const {
unsigned Depth = 0;
for (Region *R = parent; R != 0; R = R->parent)
++Depth;
return Depth;
}
void Region::print(raw_ostream &OS, bool print_tree, unsigned level) const {
if (print_tree)
OS.indent(level*2) << "[" << level << "] " << getNameStr();
else
OS.indent(level*2) << getNameStr();
OS << "\n";
if (printStyle != PrintNone) {
OS.indent(level*2) << "{\n";
OS.indent(level*2 + 2);
if (printStyle == PrintBB) {
for (const_block_iterator I = block_begin(), E = block_end(); I!=E; ++I)
OS << **I << ", "; // TODO: remove the last ","
} else if (printStyle == PrintRN) {
for (const_element_iterator I = element_begin(), E = element_end(); I!=E; ++I)
OS << **I << ", "; // TODO: remove the last ",
}
OS << "\n";
}
if (print_tree)
for (const_iterator RI = begin(), RE = end(); RI != RE; ++RI)
(*RI)->print(OS, print_tree, level+1);
if (printStyle != PrintNone)
OS.indent(level*2) << "} \n";
}
void Region::dump() const {
print(dbgs(), true, getDepth());
}
void Region::clearNodeCache() {
BBNodeMap.clear();
for (Region::iterator RI = begin(), RE = end(); RI != RE; ++RI)
(*RI)->clearNodeCache();
}
//===----------------------------------------------------------------------===//
// RegionInfo implementation
//
bool RegionInfo::isCommonDomFrontier(BasicBlock *BB, BasicBlock *entry,
BasicBlock *exit) const {
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
BasicBlock *P = *PI;
if (DT->dominates(entry, P) && !DT->dominates(exit, P))
return false;
}
return true;
}
bool RegionInfo::isRegion(BasicBlock *entry, BasicBlock *exit) const {
assert(entry && exit && "entry and exit must not be null!");
typedef DominanceFrontier::DomSetType DST;
DST *entrySuccs = &DF->find(entry)->second;
// Exit is the header of a loop that contains the entry. In this case,
// the dominance frontier must only contain the exit.
if (!DT->dominates(entry, exit)) {
for (DST::iterator SI = entrySuccs->begin(), SE = entrySuccs->end();
SI != SE; ++SI)
if (*SI != exit && *SI != entry)
return false;
return true;
}
DST *exitSuccs = &DF->find(exit)->second;
// Do not allow edges leaving the region.
for (DST::iterator SI = entrySuccs->begin(), SE = entrySuccs->end();
SI != SE; ++SI) {
if (*SI == exit || *SI == entry)
continue;
if (exitSuccs->find(*SI) == exitSuccs->end())
return false;
if (!isCommonDomFrontier(*SI, entry, exit))
return false;
}
// Do not allow edges pointing into the region.
for (DST::iterator SI = exitSuccs->begin(), SE = exitSuccs->end();
SI != SE; ++SI)
if (DT->properlyDominates(entry, *SI) && *SI != exit)
return false;
return true;
}
void RegionInfo::insertShortCut(BasicBlock *entry, BasicBlock *exit,
BBtoBBMap *ShortCut) const {
assert(entry && exit && "entry and exit must not be null!");
BBtoBBMap::iterator e = ShortCut->find(exit);
if (e == ShortCut->end())
// No further region at exit available.
(*ShortCut)[entry] = exit;
else {
// We found a region e that starts at exit. Therefore (entry, e->second)
// is also a region, that is larger than (entry, exit). Insert the
// larger one.
BasicBlock *BB = e->second;
(*ShortCut)[entry] = BB;
}
}
DomTreeNode* RegionInfo::getNextPostDom(DomTreeNode* N,
BBtoBBMap *ShortCut) const {
BBtoBBMap::iterator e = ShortCut->find(N->getBlock());
if (e == ShortCut->end())
return N->getIDom();
return PDT->getNode(e->second)->getIDom();
}
bool RegionInfo::isTrivialRegion(BasicBlock *entry, BasicBlock *exit) const {
assert(entry && exit && "entry and exit must not be null!");
unsigned num_successors = succ_end(entry) - succ_begin(entry);
if (num_successors <= 1 && exit == *(succ_begin(entry)))
return true;
return false;
}
void RegionInfo::updateStatistics(Region *R) {
++numRegions;
// TODO: Slow. Should only be enabled if -stats is used.
if (R->isSimple()) ++numSimpleRegions;
}
Region *RegionInfo::createRegion(BasicBlock *entry, BasicBlock *exit) {
assert(entry && exit && "entry and exit must not be null!");
if (isTrivialRegion(entry, exit))
return 0;
Region *region = new Region(entry, exit, this, DT);
BBtoRegion.insert(std::make_pair(entry, region));
#ifdef XDEBUG
region->verifyRegion();
#else
DEBUG(region->verifyRegion());
#endif
updateStatistics(region);
return region;
}
void RegionInfo::findRegionsWithEntry(BasicBlock *entry, BBtoBBMap *ShortCut) {
assert(entry);
DomTreeNode *N = PDT->getNode(entry);
if (!N)
return;
Region *lastRegion= 0;
BasicBlock *lastExit = entry;
// As only a BasicBlock that postdominates entry can finish a region, walk the
// post dominance tree upwards.
while ((N = getNextPostDom(N, ShortCut))) {
BasicBlock *exit = N->getBlock();
if (!exit)
break;
if (isRegion(entry, exit)) {
Region *newRegion = createRegion(entry, exit);
if (lastRegion)
newRegion->addSubRegion(lastRegion);
lastRegion = newRegion;
lastExit = exit;
}
// This can never be a region, so stop the search.
if (!DT->dominates(entry, exit))
break;
}
// Tried to create regions from entry to lastExit. Next time take a
// shortcut from entry to lastExit.
if (lastExit != entry)
insertShortCut(entry, lastExit, ShortCut);
}
void RegionInfo::scanForRegions(Function &F, BBtoBBMap *ShortCut) {
BasicBlock *entry = &(F.getEntryBlock());
DomTreeNode *N = DT->getNode(entry);
// Iterate over the dominance tree in post order to start with the small
// regions from the bottom of the dominance tree. If the small regions are
// detected first, detection of bigger regions is faster, as we can jump
// over the small regions.
for (po_iterator<DomTreeNode*> FI = po_begin(N), FE = po_end(N); FI != FE;
++FI) {
findRegionsWithEntry(FI->getBlock(), ShortCut);
}
}
Region *RegionInfo::getTopMostParent(Region *region) {
while (region->parent)
region = region->getParent();
return region;
}
void RegionInfo::buildRegionsTree(DomTreeNode *N, Region *region) {
BasicBlock *BB = N->getBlock();
// Passed region exit
while (BB == region->getExit())
region = region->getParent();
BBtoRegionMap::iterator it = BBtoRegion.find(BB);
// This basic block is a start block of a region. It is already in the
// BBtoRegion relation. Only the child basic blocks have to be updated.
if (it != BBtoRegion.end()) {
Region *newRegion = it->second;;
region->addSubRegion(getTopMostParent(newRegion));
region = newRegion;
} else {
BBtoRegion[BB] = region;
}
for (DomTreeNode::iterator CI = N->begin(), CE = N->end(); CI != CE; ++CI)
buildRegionsTree(*CI, region);
}
void RegionInfo::releaseMemory() {
BBtoRegion.clear();
if (TopLevelRegion)
delete TopLevelRegion;
TopLevelRegion = 0;
}
RegionInfo::RegionInfo() : FunctionPass(ID) {
TopLevelRegion = 0;
}
RegionInfo::~RegionInfo() {
releaseMemory();
}
void RegionInfo::Calculate(Function &F) {
// ShortCut a function where for every BB the exit of the largest region
// starting with BB is stored. These regions can be threated as single BBS.
// This improves performance on linear CFGs.
BBtoBBMap ShortCut;
scanForRegions(F, &ShortCut);
BasicBlock *BB = &F.getEntryBlock();
buildRegionsTree(DT->getNode(BB), TopLevelRegion);
}
bool RegionInfo::runOnFunction(Function &F) {
releaseMemory();
DT = &getAnalysis<DominatorTree>();
PDT = &getAnalysis<PostDominatorTree>();
DF = &getAnalysis<DominanceFrontier>();
TopLevelRegion = new Region(&F.getEntryBlock(), 0, this, DT, 0);
updateStatistics(TopLevelRegion);
Calculate(F);
return false;
}
void RegionInfo::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequiredTransitive<DominatorTree>();
AU.addRequired<PostDominatorTree>();
AU.addRequired<DominanceFrontier>();
}
void RegionInfo::print(raw_ostream &OS, const Module *) const {
OS << "Region tree:\n";
TopLevelRegion->print(OS, true, 0);
OS << "End region tree\n";
}
void RegionInfo::verifyAnalysis() const {
// Only do verification when user wants to, otherwise this expensive check
// will be invoked by PMDataManager::verifyPreservedAnalysis when
// a regionpass (marked PreservedAll) finish.
if (!VerifyRegionInfo) return;
TopLevelRegion->verifyRegionNest();
}
// Region pass manager support.
Region *RegionInfo::getRegionFor(BasicBlock *BB) const {
BBtoRegionMap::const_iterator I=
BBtoRegion.find(BB);
return I != BBtoRegion.end() ? I->second : 0;
}
Region *RegionInfo::operator[](BasicBlock *BB) const {
return getRegionFor(BB);
}
BasicBlock *RegionInfo::getMaxRegionExit(BasicBlock *BB) const {
BasicBlock *Exit = NULL;
while (true) {
// Get largest region that starts at BB.
Region *R = getRegionFor(BB);
while (R && R->getParent() && R->getParent()->getEntry() == BB)
R = R->getParent();
// Get the single exit of BB.
if (R && R->getEntry() == BB)
Exit = R->getExit();
else if (++succ_begin(BB) == succ_end(BB))
Exit = *succ_begin(BB);
else // No single exit exists.
return Exit;
// Get largest region that starts at Exit.
Region *ExitR = getRegionFor(Exit);
while (ExitR && ExitR->getParent()
&& ExitR->getParent()->getEntry() == Exit)
ExitR = ExitR->getParent();
for (pred_iterator PI = pred_begin(Exit), PE = pred_end(Exit); PI != PE;
++PI)
if (!R->contains(*PI) && !ExitR->contains(*PI))
break;
// This stops infinite cycles.
if (DT->dominates(Exit, BB))
break;
BB = Exit;
}
return Exit;
}
Region*
RegionInfo::getCommonRegion(Region *A, Region *B) const {
assert (A && B && "One of the Regions is NULL");
if (A->contains(B)) return A;
while (!B->contains(A))
B = B->getParent();
return B;
}
Region*
RegionInfo::getCommonRegion(SmallVectorImpl<Region*> &Regions) const {
Region* ret = Regions.back();
Regions.pop_back();
for (SmallVectorImpl<Region*>::const_iterator I = Regions.begin(),
E = Regions.end(); I != E; ++I)
ret = getCommonRegion(ret, *I);
return ret;
}
Region*
RegionInfo::getCommonRegion(SmallVectorImpl<BasicBlock*> &BBs) const {
Region* ret = getRegionFor(BBs.back());
BBs.pop_back();
for (SmallVectorImpl<BasicBlock*>::const_iterator I = BBs.begin(),
E = BBs.end(); I != E; ++I)
ret = getCommonRegion(ret, getRegionFor(*I));
return ret;
}
char RegionInfo::ID = 0;
INITIALIZE_PASS(RegionInfo, "regions",
"Detect single entry single exit regions", true, true);
// Create methods available outside of this file, to use them
// "include/llvm/LinkAllPasses.h". Otherwise the pass would be deleted by
// the link time optimization.
namespace llvm {
FunctionPass *createRegionInfoPass() {
return new RegionInfo();
}
}