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Fix SplitBlockPredecessors' LoopInfo updating code to handle the case

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where a loop's header is being split and it has predecessors which are not
contained by the most-nested loop which contains the loop.
This fixes PR5235.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84505 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-10-19 16:04:50 +00:00
parent dfffba6a83
commit 841a147531
2 changed files with 40 additions and 8 deletions
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28
lib/Transforms/Utils/BasicBlockUtils.cpp
View File

@ -425,14 +425,26 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
if (L) {
if (IsLoopEntry) {
if (Loop *PredLoop = LI->getLoopFor(Preds[0])) {
// Add the new block to the nearest enclosing loop (and not an
// adjacent loop).
while (PredLoop && !PredLoop->contains(BB))
PredLoop = PredLoop->getParentLoop();
if (PredLoop)
PredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
}
// Add the new block to the nearest enclosing loop (and not an
// adjacent loop). To find this, examine each of the predecessors and
// determine which loops enclose them, and select the most-nested loop
// which contains the loop containing the block being split.
Loop *InnermostPredLoop = 0;
for (unsigned i = 0; i != NumPreds; ++i)
if (Loop *PredLoop = LI->getLoopFor(Preds[i])) {
// Seek a loop which actually contains the block being split (to
// avoid adjacent loops).
while (PredLoop && !PredLoop->contains(BB))
PredLoop = PredLoop->getParentLoop();
// Select the most-nested of these loops which contains the block.
if (PredLoop &&
PredLoop->contains(BB) &&
(!InnermostPredLoop ||
InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
InnermostPredLoop = PredLoop;
}
if (InnermostPredLoop)
InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
} else {
L->addBasicBlockToLoop(NewBB, LI->getBase());
if (SplitMakesNewLoopHeader)

20
test/Transforms/LoopSimplify/unreachable-loop-pred.ll Normal file
View File

@ -0,0 +1,20 @@
; RUN: opt -S -loopsimplify -disable-output -verify-loop-info -verify-dom-info < %s
; PR5235
; When loopsimplify inserts a preheader for this loop, it should add the new
; block to the enclosing loop and not get confused by the unreachable
; bogus loop entry.
define void @is_extract_cab() nounwind {
entry:
br label %header
header: ; preds = %if.end206, %cond.end66, %if.end23
br label %while.body115
while.body115: ; preds = %9, %if.end192, %if.end101
br i1 undef, label %header, label %while.body115
foo:
br label %while.body115
}