6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-06-12 13:38:21 +00:00
Code Issues Projects Releases Wiki Activity

Convert LoopSimplify and LoopExtractor from FunctionPass to LoopPass.

Browse Source 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82990 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-09-28 14:37:51 +00:00
parent 522ce97532
commit d84db11333
4 changed files with 91 additions and 149 deletions
Download Patch File Download Diff File Expand all files Collapse all files

131
lib/Transforms/Utils/LoopSimplify.cpp
View File

@ -41,7 +41,8 @@
#include "llvm/Type.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/CFG.h"
@ -56,16 +57,17 @@ STATISTIC(NumInserted, "Number of pre-header or exit blocks inserted");
STATISTIC(NumNested , "Number of nested loops split out");
namespace {
struct VISIBILITY_HIDDEN LoopSimplify : public FunctionPass {
struct VISIBILITY_HIDDEN LoopSimplify : public LoopPass {
static char ID; // Pass identification, replacement for typeid
LoopSimplify() : FunctionPass(&ID) {}
LoopSimplify() : LoopPass(&ID) {}
// AA - If we have an alias analysis object to update, this is it, otherwise
// this is null.
AliasAnalysis *AA;
LoopInfo *LI;
DominatorTree *DT;
virtual bool runOnFunction(Function &F);
Loop *L;
virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
// We need loop information to identify the loops...
@ -76,25 +78,20 @@ namespace {
AU.addPreserved<DominatorTree>();
AU.addPreserved<DominanceFrontier>();
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<ScalarEvolution>();
AU.addPreservedID(BreakCriticalEdgesID); // No critical edges added.
}
/// verifyAnalysis() - Verify loop nest.
void verifyAnalysis() const {
#ifndef NDEBUG
LoopInfo *NLI = &getAnalysis<LoopInfo>();
for (LoopInfo::iterator I = NLI->begin(), E = NLI->end(); I != E; ++I) {
// Check the special guarantees that LoopSimplify makes.
assert((*I)->isLoopSimplifyForm());
}
#endif
assert(L->isLoopSimplifyForm() && "LoopSimplify form not preserved!");
}
private:
bool ProcessLoop(Loop *L);
bool ProcessLoop(Loop *L, LPPassManager &LPM);
BasicBlock *RewriteLoopExitBlock(Loop *L, BasicBlock *Exit);
BasicBlock *InsertPreheaderForLoop(Loop *L);
Loop *SeparateNestedLoop(Loop *L);
Loop *SeparateNestedLoop(Loop *L, LPPassManager &LPM);
void InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader);
void PlaceSplitBlockCarefully(BasicBlock *NewBB,
SmallVectorImpl<BasicBlock*> &SplitPreds,
@ -108,73 +105,19 @@ X("loopsimplify", "Canonicalize natural loops", true);
// Publically exposed interface to pass...
const PassInfo *const llvm::LoopSimplifyID = &X;
FunctionPass *llvm::createLoopSimplifyPass() { return new LoopSimplify(); }
Pass *llvm::createLoopSimplifyPass() { return new LoopSimplify(); }
/// runOnFunction - Run down all loops in the CFG (recursively, but we could do
/// it in any convenient order) inserting preheaders...
///
bool LoopSimplify::runOnFunction(Function &F) {
bool LoopSimplify::runOnLoop(Loop *l, LPPassManager &LPM) {
L = l;
bool Changed = false;
LI = &getAnalysis<LoopInfo>();
AA = getAnalysisIfAvailable<AliasAnalysis>();
DT = &getAnalysis<DominatorTree>();
// Check to see that no blocks (other than the header) in loops have
// predecessors that are not in loops. This is not valid for natural loops,
// but can occur if the blocks are unreachable. Since they are unreachable we
// can just shamelessly destroy their terminators to make them not branch into
// the loop!
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
// This case can only occur for unreachable blocks. Blocks that are
// unreachable can't be in loops, so filter those blocks out.
if (LI->getLoopFor(BB)) continue;
bool BlockUnreachable = false;
TerminatorInst *TI = BB->getTerminator();
// Check to see if any successors of this block are non-loop-header loops
// that are not the header.
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
// If this successor is not in a loop, BB is clearly ok.
Loop *L = LI->getLoopFor(TI->getSuccessor(i));
if (!L) continue;
// If the succ is the loop header, and if L is a top-level loop, then this
// is an entrance into a loop through the header, which is also ok.
if (L->getHeader() == TI->getSuccessor(i) && L->getParentLoop() == 0)
continue;
// Otherwise, this is an entrance into a loop from some place invalid.
// Either the loop structure is invalid and this is not a natural loop (in
// which case the compiler is buggy somewhere else) or BB is unreachable.
BlockUnreachable = true;
break;
}
// If this block is ok, check the next one.
if (!BlockUnreachable) continue;
// Otherwise, this block is dead. To clean up the CFG and to allow later
// loop transformations to ignore this case, we delete the edges into the
// loop by replacing the terminator.
// Remove PHI entries from the successors.
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
TI->getSuccessor(i)->removePredecessor(BB);
// Add a new unreachable instruction before the old terminator.
new UnreachableInst(TI->getContext(), TI);
// Delete the dead terminator.
if (AA) AA->deleteValue(TI);
if (!TI->use_empty())
TI->replaceAllUsesWith(UndefValue::get(TI->getType()));
TI->eraseFromParent();
Changed |= true;
}
for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
Changed |= ProcessLoop(*I);
Changed |= ProcessLoop(L, LPM);
return Changed;
}
@ -182,17 +125,37 @@ bool LoopSimplify::runOnFunction(Function &F) {
/// ProcessLoop - Walk the loop structure in depth first order, ensuring that
/// all loops have preheaders.
///
bool LoopSimplify::ProcessLoop(Loop *L) {
bool LoopSimplify::ProcessLoop(Loop *L, LPPassManager &LPM) {
bool Changed = false;
ReprocessLoop:
// Canonicalize inner loops before outer loops. Inner loop canonicalization
// can provide work for the outer loop to canonicalize.
for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
Changed |= ProcessLoop(*I);
assert(L->getBlocks()[0] == L->getHeader() &&
"Header isn't first block in loop?");
// Check to see that no blocks (other than the header) in this loop that has
// predecessors that are not in the loop. This is not valid for natural
// loops, but can occur if the blocks are unreachable. Since they are
// unreachable we can just shamelessly delete those CFG edges!
for (Loop::block_iterator BB = L->block_begin(), E = L->block_end();
BB != E; ++BB) {
if (*BB == L->getHeader()) continue;
SmallPtrSet<BasicBlock *, 4> BadPreds;
for (pred_iterator PI = pred_begin(*BB), PE = pred_end(*BB); PI != PE; ++PI)
if (!L->contains(*PI))
BadPreds.insert(*PI);
// Delete each unique out-of-loop (and thus dead) predecessor.
for (SmallPtrSet<BasicBlock *, 4>::iterator I = BadPreds.begin(),
E = BadPreds.end(); I != E; ++I) {
// Inform each successor of each dead pred.
for (succ_iterator SI = succ_begin(*I), SE = succ_end(*I); SI != SE; ++SI)
(*SI)->removePredecessor(*I);
// Zap the dead pred's terminator and replace it with unreachable.
TerminatorInst *TI = (*I)->getTerminator();
TI->replaceAllUsesWith(UndefValue::get(TI->getType()));
(*I)->getTerminator()->eraseFromParent();
new UnreachableInst((*I)->getContext(), *I);
Changed = true;
}
}
// Does the loop already have a preheader? If so, don't insert one.
BasicBlock *Preheader = L->getLoopPreheader();
@ -233,10 +196,9 @@ ReprocessLoop:
// this for loops with a giant number of backedges, just factor them into a
// common backedge instead.
if (NumBackedges < 8) {
if (Loop *NL = SeparateNestedLoop(L)) {
if (SeparateNestedLoop(L, LPM)) {
++NumNested;
// This is a big restructuring change, reprocess the whole loop.
ProcessLoop(NL);
Changed = true;
// GCC doesn't tail recursion eliminate this.
goto ReprocessLoop;
@ -472,7 +434,7 @@ void LoopSimplify::PlaceSplitBlockCarefully(BasicBlock *NewBB,
/// If we are able to separate out a loop, return the new outer loop that was
/// created.
///
Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
Loop *LoopSimplify::SeparateNestedLoop(Loop *L, LPPassManager &LPM) {
PHINode *PN = FindPHIToPartitionLoops(L, DT, AA);
if (PN == 0) return 0; // No known way to partition.
@ -506,6 +468,9 @@ Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
// L is now a subloop of our outer loop.
NewOuter->addChildLoop(L);
// Add the new loop to the pass manager queue.
LPM.insertLoopIntoQueue(NewOuter);
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
I != E; ++I)
NewOuter->addBlockEntry(*I);