[Inliner] Remove -update-return-attrs flag

This is by default on and I don't see any reason to turn it off. There's also no testing of it.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D148956

Author: aeubanks

llvm/lib/Transforms/Utils/InlineFunction.cpp

@@ -99,10 +99,6 @@ PreserveAlignmentAssumptions("preserve-alignment-assumptions-during-inlining",
   cl::init(false), cl::Hidden,
   cl::desc("Convert align attributes to assumptions during inlining."));
 
-static cl::opt<bool> UpdateReturnAttributes(
-        "update-return-attrs", cl::init(true), cl::Hidden,
-            cl::desc("Update return attributes on calls within inlined body"));
-
 static cl::opt<unsigned> InlinerAttributeWindow(
     "max-inst-checked-for-throw-during-inlining", cl::Hidden,
     cl::desc("the maximum number of instructions analyzed for may throw during "
@@ -1368,9 +1364,6 @@ static AttrBuilder IdentifyValidAttributes(CallBase &CB) {
 }
 
 static void AddReturnAttributes(CallBase &CB, ValueToValueMapTy &VMap) {
-  if (!UpdateReturnAttributes)
-    return;
-
   AttrBuilder Valid = IdentifyValidAttributes(CB);
   if (!Valid.hasAttributes())
     return;