[InlineFunction] Only replace call if there are VarArgs to forward.

[fhahn]

Summary

There is no need to replace the original call instruction if no
VarArgs need to be forwarded.

[fhahn]

Ping. This change only replaces the call site if there actually are varargs to forward.

[efriedma]

This change isn't a no-op: the code inside the if statement drops the calling convention/attributes/metadata/etc. on the call. Is that intentional?

[fhahn]

Thanks for having a look Eli! Dropping all the info is not intentional, this was missed during review. I've patch that adds debug locations D40432 and will follow this up with another patch preserving other metadata & co

[efriedma]

Okay, then this LGTM.

lib/Transforms/Utils/InlineFunction.cpp

for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E;
         CI->setTailCallKind(ChildTCK);
         InlinedMustTailCalls |= CI->isMustTailCall();
 
         // Calls inlined through a 'nounwind' call site should be marked
         // 'nounwind'.
         if (MarkNoUnwind)
           CI->setDoesNotThrow();
 
-        if (ForwardVarArgsTo && CI->getCalledFunction() == ForwardVarArgsTo) {
+        if (ForwardVarArgsTo && !VarArgsToForward.empty() &&
+            CI->getCalledFunction() == ForwardVarArgsTo) {
           SmallVector<Value*, 6> Params(CI->arg_operands());
           Params.append(VarArgsToForward.begin(), VarArgsToForward.end());
           CallInst *Call = CallInst::Create(CI->getCalledFunction(), Params, "", CI);
           CI->replaceAllUsesWith(Call);
           CI->eraseFromParent();
         }
       }
     }