LSR: fix IVUsers isSimplifiedLoopNest to perform a full domtree walk
instead of skipping the current loop.
My prior fix was incomplete because of an overzealous compile-time optimization:
Better fix for: <rdar://problem/11049788> Segmentation fault: 11 in LoopStrengthReduce
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153131 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/IVUsers.cpp b/lib/Analysis/IVUsers.cpp
index c598b72..308729f 100644
--- a/lib/Analysis/IVUsers.cpp
+++ b/lib/Analysis/IVUsers.cpp
@@ -79,22 +79,31 @@
return false;
}
-/// Return true if this loop and all loop headers that dominate it are in
-/// simplified form.
-static bool isSimplifiedLoopNest(Loop *L, const DominatorTree *DT,
- const LoopInfo *LI) {
- if (!L->isLoopSimplifyForm())
- return false;
-
- for (DomTreeNode *Rung = DT->getNode(L->getLoopPreheader());
+/// Return true if all loop headers that dominate this block are in simplified
+/// form.
+static bool isSimplifiedLoopNest(BasicBlock *BB, const DominatorTree *DT,
+ const LoopInfo *LI,
+ SmallPtrSet<Loop*,16> &SimpleLoopNests) {
+ Loop *NearestLoop = 0;
+ for (DomTreeNode *Rung = DT->getNode(BB);
Rung; Rung = Rung->getIDom()) {
- BasicBlock *BB = Rung->getBlock();
- const Loop *DomLoop = LI->getLoopFor(BB);
- if (DomLoop && DomLoop->getHeader() == BB) {
+ BasicBlock *DomBB = Rung->getBlock();
+ Loop *DomLoop = LI->getLoopFor(DomBB);
+ if (DomLoop && DomLoop->getHeader() == DomBB) {
+ // If the domtree walk reaches a loop with no preheader, return false.
if (!DomLoop->isLoopSimplifyForm())
return false;
+ // If we have already checked this loop nest, stop checking.
+ if (SimpleLoopNests.count(DomLoop))
+ break;
+ // If we have not already checked this loop nest, remember the loop
+ // header nearest to BB. The nearest loop may not contain BB.
+ if (!NearestLoop)
+ NearestLoop = DomLoop;
}
}
+ if (NearestLoop)
+ SimpleLoopNests.insert(NearestLoop);
return true;
}
@@ -137,15 +146,10 @@
if (isa<PHINode>(User) && Processed.count(User))
continue;
- Loop *UserLoop = LI->getLoopFor(User->getParent());
-
// Only consider IVUsers that are dominated by simplified loop
// headers. Otherwise, SCEVExpander will crash.
- if (UserLoop && !SimpleLoopNests.count(UserLoop)) {
- if (!isSimplifiedLoopNest(UserLoop, DT, LI))
- return false;
- SimpleLoopNests.insert(UserLoop);
- }
+ if (!isSimplifiedLoopNest(User->getParent(), DT, LI, SimpleLoopNests))
+ return false;
// Descend recursively, but not into PHI nodes outside the current loop.
// It's important to see the entire expression outside the loop to get
@@ -154,7 +158,7 @@
// If User is already in Processed, we don't want to recurse into it again,
// but do want to record a second reference in the same instruction.
bool AddUserToIVUsers = false;
- if (UserLoop != L) {
+ if (LI->getLoopFor(User->getParent()) != L) {
if (isa<PHINode>(User) || Processed.count(User) ||
!AddUsersIfInteresting(User, SimpleLoopNests)) {
DEBUG(dbgs() << "FOUND USER in other loop: " << *User << '\n'