[msan] Break the getShadow loop after matching an argument

Reviewed-by: eugenis

Differential Revision: https://reviews.llvm.org/D91320

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

@@ -1737,6 +1737,8 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
           } else {
             setOrigin(A, getCleanOrigin());
           }
+
+          break;
         }
 
         if (!FArgEagerCheck)