[LoopUnroll] Unroll loops which have exit blocks to EH pads

We were overly cautious in our analysis of loops which have invokes
which unwind to EH pads.  The loop unroll transform is safe because it
only clones blocks in the loop body, it does not try to split critical
edges involving EH pads.  Instead, move the necessary safety check to
LoopUnswitch.

N.B. The safety check for loop unswitch is covered by an existing test
which fails without it.

llvm-svn: 268357

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
index 310f41e..0e861b6 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -500,6 +500,11 @@ bool LoopUnswitch::processCurrentLoop() {
       if (!CS) continue;
       if (CS.hasFnAttr(Attribute::Convergent))
         return false;
+      // Return false if any loop blocks contain invokes whose predecessor edges
+      // we cannot split.
+      if (auto *II = dyn_cast<InvokeInst>(&I))
+        if (!II->getUnwindDest()->canSplitPredecessors())
+          return false;
     }
   }