[WinEH] Fix a case where GVN could incorrectly PRE a load into an EH pad.

Differential Revision: http://reviews.llvm.org/D14842

llvm-svn: 253908

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index 1f9630ed511..3e5f5360372 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1555,6 +1555,16 @@ bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
   for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB);
        PI != E; ++PI) {
     BasicBlock *Pred = *PI;
+
+    // If any predecessor block is an EH pad that does not allow non-PHI
+    // instructions before the terminator, we can't PRE the load.
+    if (Pred->getTerminator()->isEHPad()) {
+      DEBUG(dbgs()
+            << "COULD NOT PRE LOAD BECAUSE OF AN EH PAD PREDECESSOR '"
+            << Pred->getName() << "': " << *LI << '\n');
+      return false;
+    }
+
     if (IsValueFullyAvailableInBlock(Pred, FullyAvailableBlocks, 0)) {
       continue;
     }