[SROA] Don't falsely report that changes have occured

We would report that the function changed despite creating no new
allocas or performing any promotion.

This fixes PR27316.

llvm-svn: 267507

diff --git a/llvm/lib/Transforms/Scalar/SROA.cpp b/llvm/lib/Transforms/Scalar/SROA.cpp
index b655c74..6f65d90 100644 (file)
--- a/llvm/lib/Transforms/Scalar/SROA.cpp
+++ b/llvm/lib/Transforms/Scalar/SROA.cpp
@@ -3920,15 +3920,19 @@ AllocaInst *SROA::rewritePartition(AllocaInst &AI, AllocaSlices &AS,
       Worklist.insert(NewAI);
     }
   } else {
-    // If we can't promote the alloca, iterate on it to check for new
-    // refinements exposed by splitting the current alloca. Don't iterate on an
-    // alloca which didn't actually change and didn't get promoted.
-    if (NewAI != &AI)
-      Worklist.insert(NewAI);
-
     // Drop any post-promotion work items if promotion didn't happen.
     while (PostPromotionWorklist.size() > PPWOldSize)
       PostPromotionWorklist.pop_back();
+
+    // We couldn't promote and we didn't create a new partition, nothing
+    // happened.
+    if (NewAI == &AI)
+      return nullptr;
+
+    // If we can't promote the alloca, iterate on it to check for new
+    // refinements exposed by splitting the current alloca. Don't iterate on an
+    // alloca which didn't actually change and didn't get promoted.
+    Worklist.insert(NewAI);
   }
 
   return NewAI;