[llvm-commits] [llvm] r81363 - in /llvm/trunk: lib/Transforms/Scalar/LoopRotation.cpp lib/Transforms/Utils/BreakCriticalEdges.cpp test/Transforms/LoopUnswitch/preserve-analyses.ll
Dan Gohman
gohman at apple.com
Wed Sep 9 11:18:19 PDT 2009
Author: djg
Date: Wed Sep 9 13:18:18 2009
New Revision: 81363
URL: http://llvm.org/viewvc/llvm-project?rev=81363&view=rev
Log:
Fix SplitCriticalEdge to properly update LCSSA form when splitting a
loop exit edge -- new PHIs may be needed not only for the additional
splits that are made to preserve LoopSimplify form, but also for the
original split. Factor out the code that inserts new PHIs so that it
can be used for both. Remove LoopRotation.cpp's code for manually
updating LCSSA form, as it is now redundant. This fixes PR4934.
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp
llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp
llvm/trunk/test/Transforms/LoopUnswitch/preserve-analyses.ll
Modified: llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp?rev=81363&r1=81362&r2=81363&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp Wed Sep 9 13:18:18 2009
@@ -542,22 +542,7 @@
// Preserve canonical loop form, which means Exit block should
// have only one predecessor.
- BasicBlock *NExit = SplitEdge(L->getLoopLatch(), Exit, this);
-
- // Preserve LCSSA.
- for (BasicBlock::iterator I = Exit->begin();
- (PN = dyn_cast<PHINode>(I)); ++I) {
- unsigned N = PN->getNumIncomingValues();
- for (unsigned index = 0; index != N; ++index)
- if (PN->getIncomingBlock(index) == NExit) {
- PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName(),
- NExit->begin());
- NewPN->addIncoming(PN->getIncomingValue(index), L->getLoopLatch());
- PN->setIncomingValue(index, NewPN);
- PN->setIncomingBlock(index, NExit);
- break;
- }
- }
+ SplitEdge(L->getLoopLatch(), Exit, this);
assert(NewHeader && L->getHeader() == NewHeader &&
"Invalid loop header after loop rotation");
Modified: llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp?rev=81363&r1=81362&r2=81363&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp Wed Sep 9 13:18:18 2009
@@ -117,6 +117,38 @@
return false;
}
+/// CreatePHIsForSplitLoopExit - When a loop exit edge is split, LCSSA form
+/// may require new PHIs in the new exit block. This function inserts the
+/// new PHIs, as needed. Preds is a list of preds inside the loop, SplitBB
+/// is the new loop exit block, and DestBB is the old loop exit, now the
+/// successor of SplitBB.
+static void CreatePHIsForSplitLoopExit(SmallVectorImpl<BasicBlock *> &Preds,
+ BasicBlock *SplitBB,
+ BasicBlock *DestBB) {
+ // SplitBB shouldn't have anything non-trivial in it yet.
+ assert(SplitBB->getFirstNonPHI() == SplitBB->getTerminator() &&
+ "SplitBB has non-PHI nodes!");
+
+ // For each PHI in the destination block...
+ for (BasicBlock::iterator I = DestBB->begin();
+ PHINode *PN = dyn_cast<PHINode>(I); ++I) {
+ unsigned Idx = PN->getBasicBlockIndex(SplitBB);
+ Value *V = PN->getIncomingValue(Idx);
+ // If the input is a PHI which already satisfies LCSSA, don't create
+ // a new one.
+ if (const PHINode *VP = dyn_cast<PHINode>(V))
+ if (VP->getParent() == SplitBB)
+ continue;
+ // Otherwise a new PHI is needed. Create one and populate it.
+ PHINode *NewPN = PHINode::Create(PN->getType(), "split",
+ SplitBB->getTerminator());
+ for (unsigned i = 0, e = Preds.size(); i != e; ++i)
+ NewPN->addIncoming(V, Preds[i]);
+ // Update the original PHI.
+ PN->setIncomingValue(Idx, NewPN);
+ }
+}
+
/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
/// split the critical edge. This will update DominatorTree and
/// DominatorFrontier information if it is available, thus calling this pass
@@ -285,6 +317,16 @@
// the loop, to maintain a LoopSimplify guarantee.
if (!TIL->contains(DestBB) &&
P->mustPreserveAnalysisID(LoopSimplifyID)) {
+ assert(!TIL->contains(NewBB) &&
+ "Split point for loop exit is contained in loop!");
+
+ // Update LCSSA form in the newly created exit block.
+ if (P->mustPreserveAnalysisID(LCSSAID)) {
+ SmallVector<BasicBlock *, 1> OrigPred;
+ OrigPred.push_back(TIBB);
+ CreatePHIsForSplitLoopExit(OrigPred, NewBB, DestBB);
+ }
+
// For each unique exit block...
SmallVector<BasicBlock *, 4> ExitBlocks;
TIL->getExitBlocks(ExitBlocks);
@@ -292,41 +334,26 @@
// Collect all the preds that are inside the loop, and note
// whether there are any preds outside the loop.
SmallVector<BasicBlock *, 4> Preds;
- bool AllPredsInLoop = false;
+ bool HasPredOutsideOfLoop = false;
BasicBlock *Exit = ExitBlocks[i];
for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit);
I != E; ++I)
if (TIL->contains(*I))
Preds.push_back(*I);
else
- AllPredsInLoop = true;
+ HasPredOutsideOfLoop = true;
// If there are any preds not in the loop, we'll need to split
// the edges. The Preds.empty() check is needed because a block
// may appear multiple times in the list. We can't use
// getUniqueExitBlocks above because that depends on LoopSimplify
// form, which we're in the process of restoring!
- if (Preds.empty() || !AllPredsInLoop) continue;
- BasicBlock *NewBB = SplitBlockPredecessors(Exit,
- Preds.data(), Preds.size(),
- "split", P);
- // Update LCSSA form by creating new PHIs in the new exit blocks
- // as needed.
- if (P->mustPreserveAnalysisID(LCSSAID))
- for (BasicBlock::iterator I = Exit->begin();
- PHINode *PN = dyn_cast<PHINode>(I); ++I) {
- unsigned Idx = PN->getBasicBlockIndex(NewBB);
- Value *V = PN->getIncomingValue(Idx);
- // If the PHI is already suitable, don't create a new one.
- if (PHINode *VP = dyn_cast<PHINode>(V))
- if (VP->getParent() == NewBB)
- continue;
- // A new PHI is needed. Create one and populate it.
- PHINode *NewPN =
- PHINode::Create(PN->getType(), "split", NewBB->getTerminator());
- for (unsigned i = 0, e = Preds.size(); i != e; ++i)
- NewPN->addIncoming(V, Preds[i]);
- PN->setIncomingValue(Idx, NewPN);
- }
+ if (!Preds.empty() && HasPredOutsideOfLoop) {
+ BasicBlock *NewExitBB =
+ SplitBlockPredecessors(Exit, Preds.data(), Preds.size(),
+ "split", P);
+ if (P->mustPreserveAnalysisID(LCSSAID))
+ CreatePHIsForSplitLoopExit(Preds, NewExitBB, Exit);
+ }
}
}
// LCSSA form was updated above for the case where LoopSimplify is
Modified: llvm/trunk/test/Transforms/LoopUnswitch/preserve-analyses.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/preserve-analyses.ll?rev=81363&r1=81362&r2=81363&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnswitch/preserve-analyses.ll (original)
+++ llvm/trunk/test/Transforms/LoopUnswitch/preserve-analyses.ll Wed Sep 9 13:18:18 2009
@@ -93,3 +93,37 @@
return: ; preds = %bb8, %bb
ret void
}
+
+; This function requires special handling to preserve LCSSA form.
+; PR4934
+
+define void @pnp_check_irq() nounwind noredzone {
+entry:
+ %conv56 = trunc i64 undef to i32 ; <i32> [#uses=1]
+ br label %while.cond.i
+
+while.cond.i: ; preds = %while.cond.i.backedge, %entry
+ %call.i25 = call i8* @pci_get_device() nounwind noredzone ; <i8*> [#uses=2]
+ br i1 undef, label %if.then65, label %while.body.i
+
+while.body.i: ; preds = %while.cond.i
+ br i1 undef, label %if.then31.i.i, label %while.cond.i.backedge
+
+while.cond.i.backedge: ; preds = %if.then31.i.i, %while.body.i
+ br label %while.cond.i
+
+if.then31.i.i: ; preds = %while.body.i
+ switch i32 %conv56, label %while.cond.i.backedge [
+ i32 14, label %if.then42.i.i
+ i32 15, label %if.then42.i.i
+ ]
+
+if.then42.i.i: ; preds = %if.then31.i.i, %if.then31.i.i
+ %call.i25.lcssa48 = phi i8* [ %call.i25, %if.then31.i.i ], [ %call.i25, %if.then31.i.i ] ; <i8*> [#uses=0]
+ unreachable
+
+if.then65: ; preds = %while.cond.i
+ unreachable
+}
+
+declare i8* @pci_get_device() noredzone
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