[Utils] isLegalToPromote - Fix missing null check before writing to FailureReason.

The FailureReason input parameter maybe null, we check this in all other cases in the method but this one was missed somehow.

Fixes clang-tidy warning.

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/CallPromotionUtils.cpp b/llvm/lib/Transforms/Utils/CallPromotionUtils.cpp
index 5a47c1f..7141e4b 100644
--- a/llvm/lib/Transforms/Utils/CallPromotionUtils.cpp
+++ b/llvm/lib/Transforms/Utils/CallPromotionUtils.cpp
@@ -430,10 +430,11 @@ bool llvm::isLegalToPromote(const CallBase &CB, Function *Callee,
     }
   }
   for (; I < NumArgs; I++) {
-    // Vararg functions can have more arguments than paramters.
+    // Vararg functions can have more arguments than parameters.
     assert(Callee->isVarArg());
     if (CB.paramHasAttr(I, Attribute::StructRet)) {
-      *FailureReason = "SRet arg to vararg function";
+      if (FailureReason)
+        *FailureReason = "SRet arg to vararg function";
       return false;
     }
   }