[Inliner] Add the callsites called function return attributes to set addable attributes

[goldstein.w.n]

Summary

We can do this by just querying attribute in the callsite itself. This
is both cleaner code and produces better results.

[nikic]

llvm/lib/Transforms/Utils/InlineFunction.cpp

1346

This is going to intern a new AttributeSet just to turn it back into an AttrBuilder.

For this particular usage, I don't get why this is using AttrBuilder at all. You can replace the AB uses below with querying attributes on CB directly.

[goldstein.w.n]

Just use CB attrs

[nikic]

LGTM

llvm/lib/Transforms/Utils/InlineFunction.cpp

static bool MayContainThrowingOrExitingCall(Instruction *Begin,
 
   assert(Begin->getParent() == End->getParent() &&
          "Expected to be in same basic block!");
   return !llvm::isGuaranteedToTransferExecutionToSuccessor(
       Begin->getIterator(), End->getIterator(), InlinerAttributeWindow + 1);
 }
 
 static AttrBuilder IdentifyValidAttributes(CallBase &CB) {
-
-  AttrBuilder AB(CB.getContext(), CB.getAttributes().getRetAttrs());
-  if (!AB.hasAttributes())
-    return AB;
   AttrBuilder Valid(CB.getContext());
   // Only allow these white listed attributes to be propagated back to the
   // callee. This is because other attributes may only be valid on the call
   // itself, i.e. attributes such as signext and zeroext.
-  if (auto DerefBytes = AB.getDereferenceableBytes())
+  if (auto DerefBytes = CB.getRetDereferenceableBytes())
     Valid.addDereferenceableAttr(DerefBytes);
-  if (auto DerefOrNullBytes = AB.getDereferenceableOrNullBytes())
+  if (auto DerefOrNullBytes = CB.getRetDereferenceableOrNullBytes())
     Valid.addDereferenceableOrNullAttr(DerefOrNullBytes);
-  if (AB.contains(Attribute::NoAlias))
+  if (CB.hasRetAttr(Attribute::NoAlias))
     Valid.addAttribute(Attribute::NoAlias);
-  if (AB.contains(Attribute::NonNull))
+  if (CB.hasRetAttr(Attribute::NonNull))
     Valid.addAttribute(Attribute::NonNull);
   return Valid;
 }
 
 static void AddReturnAttributes(CallBase &CB, ValueToValueMapTy &VMap) {
   AttrBuilder Valid = IdentifyValidAttributes(CB);
   if (!Valid.hasAttributes())
     return;

llvm/test/Transforms/Inline/nonnull.ll

 ; CHECK-NEXT:    ret ptr [[R]]
 ;
   %r = call ptr @buz() willreturn nounwind
   ret ptr %r
 }
 
 define ptr @caller7() {
 ; CHECK-LABEL: define ptr @caller7() {
-; CHECK-NEXT:    [[R_I:%.*]] = call ptr @buz() #[[ATTR0]]
+; CHECK-NEXT:    [[R_I:%.*]] = call nonnull ptr @buz() #[[ATTR0]]
 ; CHECK-NEXT:    ret ptr [[R_I]]
 ;
   %r = call ptr @callee7()
   ret ptr %r
 }
 
 define nonnull ptr @callee8() {
 ; CHECK-LABEL: define nonnull ptr @callee8() {