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-rw-r--r--llvm/lib/Transforms/Utils/LoopSimplify.cpp131
1 files changed, 48 insertions, 83 deletions
diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
index 2ff9f8be4bb..ffa12bfb7f0 100644
--- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
@@ -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);
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