Don't optimize the landing pad exit block.

One way to exit the loop is through an unwind edge. However, that may involve
splitting the critical edge of the landing pad, which is non-trivial. Prevent
the transformation from rewriting the landing pad exit loop block.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137871 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/LoopSimplify.cpp b/lib/Transforms/Utils/LoopSimplify.cpp
index 6a99769..b019684 100644 (file)
--- a/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/lib/Transforms/Utils/LoopSimplify.cpp
@@ -398,6 +398,9 @@ BasicBlock *LoopSimplify::InsertPreheaderForLoop(Loop *L) {
 /// blocks.  This method is used to split exit blocks that have predecessors
 /// outside of the loop.
 BasicBlock *LoopSimplify::RewriteLoopExitBlock(Loop *L, BasicBlock *Exit) {
+  // Don't split a landing pad block.
+  if (Exit->isLandingPad()) return 0;
+
   SmallVector<BasicBlock*, 8> LoopBlocks;
   for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit); I != E; ++I) {
     BasicBlock *P = *I;
@@ -746,18 +749,29 @@ void LoopSimplify::verifyAnalysis() const {
     (void)HasIndBrPred;
   }
 
-  // Indirectbr can interfere with exit block canonicalization.
+  // Indirectbr and LandingPad can interfere with exit block canonicalization.
   if (!L->hasDedicatedExits()) {
     bool HasIndBrExiting = false;
+    bool HasLPadExiting = false;
     SmallVector<BasicBlock*, 8> ExitingBlocks;
     L->getExitingBlocks(ExitingBlocks);
-    for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i)
+    for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
       if (isa<IndirectBrInst>((ExitingBlocks[i])->getTerminator())) {
         HasIndBrExiting = true;
         break;
       }
-    assert(HasIndBrExiting &&
+      if (const InvokeInst *II =
+          dyn_cast<InvokeInst>(ExitingBlocks[i]->getTerminator())) {
+        if (L->contains(II->getNormalDest()) &&
+            !L->contains(II->getUnwindDest())) {
+          HasLPadExiting = true;
+          break;
+        }
+      }
+    }
+
+    assert((HasIndBrExiting || HasLPadExiting) &&
            "LoopSimplify has no excuse for missing exit block info!");
-    (void)HasIndBrExiting;
+    (void)HasIndBrExiting; (void)HasLPadExiting;
   }
 }