Set `BBF_RUN_RARELY` for a scratch first BB if called count is 0.

Just what it says on the tin.

Fixes VSO 469624.

diff --git a/src/jit/flowgraph.cpp b/src/jit/flowgraph.cpp
index 5dab6bb..0c8a28e 100644 (file)
--- a/src/jit/flowgraph.cpp
+++ b/src/jit/flowgraph.cpp
@@ -12836,6 +12836,10 @@ void Compiler::fgComputeEdgeWeights()
         if (fgFirstBBisScratch())
         {
             fgFirstBB->setBBProfileWeight(fgCalledCount);
+            if (fgFirstBB->bbWeight == 0)
+            {
+                fgFirstBB->bbFlags |= BBF_RUN_RARELY;
+            }
         }
 
 #if DEBUG