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Make isLCSSA ignore uses in blocks not reachable from the entry block,

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as LCSSA no longer transforms such uses.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98033 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-03-09 01:53:33 +00:00
parent 5b9062cb3a
commit cbac7f1630
2 changed files with 41 additions and 3 deletions
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17
lib/Analysis/LoopInfo.cpp
View File

@ -264,6 +264,13 @@ unsigned Loop::getSmallConstantTripMultiple() const {
/// isLCSSAForm - Return true if the Loop is in LCSSA form
bool Loop::isLCSSAForm() const {
// Collect all the reachable blocks in the function, for fast lookups.
SmallPtrSet<BasicBlock *, 32> ReachableBBs;
BasicBlock *EntryBB = getHeader()->getParent()->begin();
for (df_iterator<BasicBlock *> NI = df_begin(EntryBB),
NE = df_end(EntryBB); NI != NE; ++NI)
ReachableBBs.insert(*NI);
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallPtrSet<BasicBlock *, 16> LoopBBs(block_begin(), block_end());
@ -277,9 +284,13 @@ bool Loop::isLCSSAForm() const {
if (PHINode *P = dyn_cast<PHINode>(*UI))
UserBB = P->getIncomingBlock(UI);
// Check the current block, as a fast-path. Most values are used in
// the same block they are defined in.
if (UserBB != BB && !LoopBBs.count(UserBB))
// Check the current block, as a fast-path, before checking whether
// the use is anywhere in the loop. Most values are used in the same
// block they are defined in. Also, blocks not reachable from the
// entry are special; uses in them don't need to go through PHIs.
if (UserBB != BB &&
!LoopBBs.count(UserBB) &&
ReachableBBs.count(UserBB))
return false;
}
}

27
test/Transforms/LCSSA/unreachable-use.ll Normal file
View File

@ -0,0 +1,27 @@
; RUN: opt < %s -lcssa -S -verify-loop-info | grep {\[%\]tmp33 = load i1\\*\\* \[%\]tmp}
; PR6546
; LCSSA doesn't need to transform uses in blocks not reachable
; from the entry block.
define fastcc void @dfs() nounwind {
bb:
br label %bb44
bb44:
br i1 undef, label %bb7, label %bb45
bb7:
%tmp = bitcast i1** undef to i1**
br label %bb15
bb15:
br label %bb44
bb32:
%tmp33 = load i1** %tmp, align 8
br label %bb45
bb45:
unreachable
}