[lanai] Exit early in Mem Alu combiner if sentinel reach.

LanaiMemAluCombiner could try to query the debug value of a list sentinel. Add check to exit early instead.

llvm-svn: 279497

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/Target/Lanai/LanaiMemAluCombiner.cpp b/llvm/lib/Target/Lanai/LanaiMemAluCombiner.cpp
index c5a46143ee5..64e784bf0d4 100644
--- a/llvm/lib/Target/Lanai/LanaiMemAluCombiner.cpp
+++ b/llvm/lib/Target/Lanai/LanaiMemAluCombiner.cpp
@@ -339,6 +339,9 @@ MbbIterator LanaiMemAluCombiner::findClosestSuitableAluInstr(
   while (First != Last) {
     Decrement ? --First : ++First;
 
+    if (First == Last)
+      break;
+
     // Skip over debug instructions
     if (First->isDebugValue())
       continue;