Address review comments and minor cleanup.

* Added support for emitting ref metadata on functions.
* Added testing for ref metadata on functions.
* Fixed up lang ref description.
* Renamed tests to match metadatas nameing.

Author: mandlebug

llvm/docs/LangRef.rst

@@ -8673,21 +8673,21 @@ denoting if the type contains a pointer.
 '``ref``' Metadata
 ^^^^^^^^^^^^^^^^^^
 
-The ``ref`` metadata may be attached to a global variable definition with a
-single argument that references a global object. The metadata is lowered to a
-.ref directive which will emit a relocation introducing an explicit dependence
-to the referenced symbol. This is typically used when there is some implicit
-dependence between the symbols that is otherwise opaque to the linker. One such
-example is metadata which is accessed by a runtime with associated
-``__start_<section_name>`` and ``__stop_<section_name>`` symbols.
+The ``ref`` metadata may be attached to a function or global variable
+definition with a single argument that references a global object.
+This is typically used when there is some implicit dependence between the
+symbols that is otherwise opaque to the linker. One such example is metadata
+which is accessed by a runtime with associated ``__start_<section_name>`` and
+``__stop_<section_name>`` symbols.
+
+It does not have any effect on non-XCOFF targets.
 
 This metadata lowers to the .ref assembly directive which will add a relocation
 representing an implicit reference from the section the global belongs to, to
-the associated symbol. This link will keep the associated symbol alive if the
-section is not garbage collected. More than one associated node can be attached
-to the same global variable.
+the associated symbol. This link will keep the referenced symbol alive if the
+section is not garbage collected. More than one ref node can be attached
+to the same function or global variable.
 
-It does not have any effect on non-XCOFF targets.
 
 Example:
 

llvm/lib/IR/Verifier.cpp

@@ -777,8 +777,6 @@ void Verifier::visitGlobalValue(const GlobalValue &GV) {
         Check(MD->getNumOperands() == 1, "ref metadata must have one operand",
               &GV, MD);
         const Metadata *Op = MD->getOperand(0).get();
-        Check(Op, "ref metadata must have a global value", GO, MD);
-
         const auto *VM = dyn_cast_or_null<ValueAsMetadata>(Op);
         Check(VM, "ref metadata must be ValueAsMetadata", GO, MD);
         if (VM) {

llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp

@@ -2899,10 +2899,16 @@ void PPCAIXAsmPrinter::emitFunctionEntryLabel() {
   if (!TM.getFunctionSections() || MF->getFunction().hasSection())
     PPCAsmPrinter::emitFunctionEntryLabel();
 
+  const Function *F = &MF->getFunction();
+
   // Emit aliasing label for function entry point label.
-  for (const GlobalAlias *Alias : GOAliasMap[&MF->getFunction()])
+  for (const GlobalAlias *Alias : GOAliasMap[F])
     OutStreamer->emitLabel(
         getObjFileLowering().getFunctionEntryPointSymbol(Alias, TM));
+
+  if (F->hasMetadata(LLVMContext::MD_ref)) {
+    emitRefMetadata(F);
+  }
 }
 
 void PPCAIXAsmPrinter::emitPGORefs(Module &M) {

llvm/test/CodeGen/PowerPC/aix-func-ref.ll

@@ -0,0 +1,31 @@
+; RUN: llc -verify-machineinstrs -mtriple powerpc-ibm-aix-xcoff < %s | \
+; RUN: FileCheck %s -check-prefixes=NOFSECTS,CHECK
+
+; RUN: llc -verify-machineinstrs -mtriple powerpc-ibm-aix-xcoff --function-sections < %s | \
+; RUN: FileCheck %s -check-prefixes=FSECTS,CHECK
+
+@a = global i32 1
+@b = global i32 2
+@c = global i32 3
+
+define i32 @foo() !ref !0 {
+  ret i32 0
+}
+
+define i32 @bar() !ref !1 !ref !2 {
+  ret i32 0
+}
+
+!0 = !{ptr @a}
+!1 = !{ptr @b}
+!2 = !{ptr @c}
+
+; NOFSECTS:  .foo:
+; FSECTS:    .csect .foo[PR]
+; CHECK:       .ref a[RW]
+
+; NOFSECTS:  .bar:
+; FSECTS:    .csect .bar[PR]
+; CHECK:       .ref b[RW]
+; CHECK:       .ref c[RW]
+

llvm/test/CodeGen/PowerPC/aix-associated-metadata.ll renamed to llvm/test/CodeGen/PowerPC/aix-ref-metadata.ll

@@ -0,0 +1,12 @@
+; RUN: llvm-as < %s -o /dev/null 2>&1
+
+@a = global i32 1
+@b = global i32 2
+@c = global i32 3, !ref !0
+
+define i32 @foo() !ref !1 {
+  ret i32 0
+}
+
+!0 = !{ptr @a}
+!1 = !{ptr @b}

llvm/test/Verifier/ref-func.ll

@@ -25,4 +25,3 @@
 ; CHECK: ref metadata must have one operand
 ; CHECK: ptr @d
 ; CHECK: !3 = !{ptr @c, ptr @a}
-