[llvm-commits] [llvm] r123072 - in /llvm/trunk: lib/Transforms/Scalar/LoopRotation.cpp test/Transforms/LoopRotate/phi-duplicate.ll
Chris Lattner
sabre at nondot.org
Sat Jan 8 10:52:51 PST 2011
Author: lattner
Date: Sat Jan 8 12:52:51 2011
New Revision: 123072
URL: http://llvm.org/viewvc/llvm-project?rev=123072&view=rev
Log:
Three major changes:
1. Rip out LoopRotate's domfrontier updating code. It isn't
needed now that LICM doesn't use DF and it is super complex
and gross.
2. Make DomTree updating code a lot simpler and faster. The
old loop over all the blocks was just to find a block??
3. Change the code that inserts the new preheader to just use
SplitCriticalEdge instead of doing an overcomplex
reimplementation of it.
No behavior change, except for the name of the inserted preheader.
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp
llvm/trunk/test/Transforms/LoopRotate/phi-duplicate.ll
Modified: llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp?rev=123072&r1=123071&r2=123072&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp Sat Jan 8 12:52:51 2011
@@ -15,7 +15,6 @@
#include "llvm/Transforms/Scalar.h"
#include "llvm/Function.h"
#include "llvm/Analysis/CodeMetrics.h"
-#include "llvm/Analysis/DominanceFrontier.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/ScalarEvolution.h"
@@ -46,7 +45,6 @@
// LCSSA form makes instruction renaming easier.
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreserved<DominatorTree>();
- AU.addPreserved<DominanceFrontier>();
AU.addRequired<LoopInfo>();
AU.addPreserved<LoopInfo>();
AU.addRequiredID(LoopSimplifyID);
@@ -296,7 +294,7 @@
// Also, since this original header only has one predecessor, zap its
// PHI nodes, which are now trivial.
FoldSingleEntryPHINodes(OrigHeader);
-
+
// TODO: We could just go ahead and merge OrigHeader into its predecessor
// at this point, if we don't mind updating dominator info.
@@ -309,130 +307,37 @@
}
-/// After loop rotation, loop pre-header has multiple sucessors.
-/// Insert one forwarding basic block to ensure that loop pre-header
-/// has only one successor.
+/// Update LoopInfo, DominatorTree, and DomFrontiers to reflect the CFG change
+/// we just made. Then split edges as necessary to preserve LoopSimplify form.
void LoopRotate::preserveCanonicalLoopForm(Loop *L, BasicBlock *OrigHeader,
BasicBlock *OrigPreHeader,
BasicBlock *OrigLatch,
BasicBlock *NewHeader,
BasicBlock *Exit) {
-
- // Right now original pre-header has two successors, new header and
- // exit block. Insert new block between original pre-header and
- // new header such that loop's new pre-header has only one successor.
- BasicBlock *NewPreHeader =
- BasicBlock::Create(OrigHeader->getContext(), "bb.nph",
- OrigHeader->getParent(), NewHeader);
- if (Loop *PL = LI->getLoopFor(OrigPreHeader))
- PL->addBasicBlockToLoop(NewPreHeader, LI->getBase());
- BranchInst::Create(NewHeader, NewPreHeader);
-
- BranchInst *OrigPH_BI = cast<BranchInst>(OrigPreHeader->getTerminator());
- if (OrigPH_BI->getSuccessor(0) == NewHeader)
- OrigPH_BI->setSuccessor(0, NewPreHeader);
- else {
- assert(OrigPH_BI->getSuccessor(1) == NewHeader &&
- "Unexpected original pre-header terminator");
- OrigPH_BI->setSuccessor(1, NewPreHeader);
- }
-
- PHINode *PN;
- for (BasicBlock::iterator I = NewHeader->begin();
- (PN = dyn_cast<PHINode>(I)); ++I) {
- int index = PN->getBasicBlockIndex(OrigPreHeader);
- assert(index != -1 && "Expected incoming value from Original PreHeader");
- PN->setIncomingBlock(index, NewPreHeader);
- assert(PN->getBasicBlockIndex(OrigPreHeader) == -1 &&
- "Expected only one incoming value from Original PreHeader");
- }
+ assert(L->getHeader() == NewHeader && "Latch block is our new header");
if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
- DT->addNewBlock(NewPreHeader, OrigPreHeader);
- DT->changeImmediateDominator(L->getHeader(), NewPreHeader);
+ // Since OrigPreheader now has the conditional branch to Exit block, it is
+ // the dominator of Exit.
DT->changeImmediateDominator(Exit, OrigPreHeader);
- for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
- BI != BE; ++BI) {
- BasicBlock *B = *BI;
- if (L->getHeader() != B) {
- DomTreeNode *Node = DT->getNode(B);
- if (Node && Node->getBlock() == OrigHeader)
- DT->changeImmediateDominator(*BI, L->getHeader());
- }
- }
+ DT->changeImmediateDominator(NewHeader, OrigPreHeader);
+
+ // Update OrigHeader to be dominated by the new header block.
DT->changeImmediateDominator(OrigHeader, OrigLatch);
}
-
- if (DominanceFrontier *DF = getAnalysisIfAvailable<DominanceFrontier>()) {
- // New Preheader's dominance frontier is Exit block.
- DominanceFrontier::DomSetType NewPHSet;
- NewPHSet.insert(Exit);
- DF->addBasicBlock(NewPreHeader, NewPHSet);
-
- // New Header's dominance frontier now includes itself and Exit block
- DominanceFrontier::iterator HeadI = DF->find(L->getHeader());
- if (HeadI != DF->end()) {
- DominanceFrontier::DomSetType & HeaderSet = HeadI->second;
- HeaderSet.clear();
- HeaderSet.insert(L->getHeader());
- HeaderSet.insert(Exit);
- } else {
- DominanceFrontier::DomSetType HeaderSet;
- HeaderSet.insert(L->getHeader());
- HeaderSet.insert(Exit);
- DF->addBasicBlock(L->getHeader(), HeaderSet);
- }
-
- // Original header (new Loop Latch)'s dominance frontier is Exit.
- DominanceFrontier::iterator LatchI = DF->find(L->getLoopLatch());
- if (LatchI != DF->end()) {
- DominanceFrontier::DomSetType &LatchSet = LatchI->second;
- LatchSet = LatchI->second;
- LatchSet.clear();
- LatchSet.insert(Exit);
- } else {
- DominanceFrontier::DomSetType LatchSet;
- LatchSet.insert(Exit);
- DF->addBasicBlock(L->getHeader(), LatchSet);
- }
-
- // If a loop block dominates new loop latch then add to its frontiers
- // new header and Exit and remove new latch (which is equal to original
- // header).
- BasicBlock *NewLatch = L->getLoopLatch();
-
- assert(NewLatch == OrigHeader && "NewLatch is inequal to OrigHeader");
-
- if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
- for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
- BI != BE; ++BI) {
- BasicBlock *B = *BI;
- if (!DT->dominates(B, NewLatch)) continue;
-
- DominanceFrontier::iterator BDFI = DF->find(B);
- if (BDFI != DF->end()) {
- DominanceFrontier::DomSetType &BSet = BDFI->second;
- BSet.erase(NewLatch);
- BSet.insert(L->getHeader());
- BSet.insert(Exit);
- } else {
- DominanceFrontier::DomSetType BSet;
- BSet.insert(L->getHeader());
- BSet.insert(Exit);
- DF->addBasicBlock(B, BSet);
- }
- }
- }
- }
-
- // Preserve canonical loop form, which means Exit block should
- // have only one predecessor.
- SplitEdge(L->getLoopLatch(), Exit, this);
+
+ // Right now OrigPreHeader has two successors, NewHeader and ExitBlock, and
+ // thus is not a preheader anymore. Split the edge to form a real preheader.
+ BasicBlock *NewPH = SplitCriticalEdge(OrigPreHeader, NewHeader, this);
+ NewPH->setName(NewHeader->getName() + ".lr.ph");
+
+ // Preserve canonical loop form, which means Exit block should have only one
+ // predecessor.
+ SplitCriticalEdge(L->getLoopLatch(), Exit, this);
assert(NewHeader && L->getHeader() == NewHeader &&
"Invalid loop header after loop rotation");
- assert(NewPreHeader && L->getLoopPreheader() == NewPreHeader &&
+ assert(L->getLoopPreheader() == NewPH &&
"Invalid loop preheader after loop rotation");
- assert(L->getLoopLatch() &&
- "Invalid loop latch after loop rotation");
+ assert(L->getLoopLatch() && "Invalid loop latch after loop rotation");
}
Modified: llvm/trunk/test/Transforms/LoopRotate/phi-duplicate.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopRotate/phi-duplicate.ll?rev=123072&r1=123071&r2=123072&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopRotate/phi-duplicate.ll (original)
+++ llvm/trunk/test/Transforms/LoopRotate/phi-duplicate.ll Sat Jan 8 12:52:51 2011
@@ -34,9 +34,9 @@
; CHECK: define void @test
; CHECK-NEXT: entry:
-; CHECK-NEXT: br i1 true, label %bb.nph, label %for.end
+; CHECK-NEXT: br i1 true, label %for.body.lr.ph, label %for.end
; CHECK-NOT: :
-; CHECK: bb.nph:
+; CHECK: for.body.lr.ph:
; CHECK-NEXT: br label %for.body
; CHECK-NOT: :
; CHECK: for.body:
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