Make isLCSSA ignore uses in blocks not reachable from the entry block,
as LCSSA no longer transforms such uses.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98033 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp
index 453af5a..2139c29 100644
--- a/lib/Analysis/LoopInfo.cpp
+++ b/lib/Analysis/LoopInfo.cpp
@@ -264,6 +264,13 @@
/// 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 @@
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;
}
}