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[ShrinkWrapping] Fix an infinite loop while looking for restore point.

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This may happen when the input program itself contains an infinite loop with no
exit block. In that case, we would fail to find a block post-dominating the loop
such that this block is outside of the loop.

This fixes PR24823.
Working on reducing the test case.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247710 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Quentin Colombet 2015-09-15 18:19:39 +00:00
parent 5332ea03d1
commit 07400eaee0
1 changed files with 8 additions and 0 deletions
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8
lib/CodeGen/ShrinkWrap.cpp
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@ -309,6 +309,14 @@ void ShrinkWrap::updateSaveRestorePoints(MachineBasicBlock &MBB) {
}
}
else {
// If the loop does not exit, there is no point in looking
// for a post-dominator outside the loop.
SmallVector<MachineBasicBlock*, 4> ExitBlocks;
MLI->getLoopFor(Restore)->getExitingBlocks(ExitBlocks);
if (ExitBlocks.empty()) {
Restore = nullptr;
break;
}
// Push Restore outside of this loop if immediate post-dominator is
// different from restore block. If immediate post-dominator is not
// different, bail out.