[outliners] Turn nooutline into an Enum Attribute (#163665)

This change turns the `"nooutline"` attribute into an enum attribute
called `nooutline`, and adds an auto-upgrader for bitcode to make the
same change to existing IR.

This IR attribute disables both the Machine Outliner (enabled at Oz for
some targets), and the IR Outliner (disabled by default).

llvm/docs/LangRef.rst

@@ -2766,7 +2766,7 @@ For example:
     to signify an unbounded maximum. The syntax `vscale_range(<val>)` can be
     used to set both `min` and `max` to the same value. Functions that don't
     include this attribute make no assumptions about the value of `vscale`.
-``"nooutline"``
+``nooutline``
     This attribute indicates that outlining passes should not modify the
     function.
 ``nocreateundeforpoison``

llvm/docs/ReleaseNotes.md

@@ -66,6 +66,9 @@ Changes to the LLVM IR
 * "denormal-fp-math" and "denormal-fp-math-f32" string attributes were
   migrated to first-class denormal_fpenv attribute.
 
+* The `"nooutline"` attribute is now writen as `nooutline`. Existing IR and
+  bitcode will be automatically updated.
+
 Changes to LLVM infrastructure
 ------------------------------
 

llvm/include/llvm/Bitcode/LLVMBitCodes.h

@@ -808,6 +808,7 @@ enum AttributeKindCodes {
   ATTR_KIND_SANITIZE_ALLOC_TOKEN = 104,
   ATTR_KIND_NO_CREATE_UNDEF_OR_POISON = 105,
   ATTR_KIND_DENORMAL_FPENV = 106,
+  ATTR_KIND_NOOUTLINE = 107,
 };
 
 enum ComdatSelectionKindCodes {

llvm/include/llvm/IR/Attributes.td

@@ -212,6 +212,9 @@ def NoImplicitFloat : EnumAttr<"noimplicitfloat", IntersectPreserve, [FnAttr]>;
 /// inline=never.
 def NoInline : EnumAttr<"noinline", IntersectPreserve, [FnAttr]>;
 
+/// nooutline
+def NoOutline : EnumAttr<"nooutline", IntersectPreserve, [FnAttr]>;
+
 /// Function is called early and/or often, so lazy binding isn't worthwhile.
 def NonLazyBind : EnumAttr<"nonlazybind", IntersectPreserve, [FnAttr]>;
 

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -2271,6 +2271,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
     return Attribute::NoCreateUndefOrPoison;
   case bitc::ATTR_KIND_DENORMAL_FPENV:
     return Attribute::DenormalFPEnv;
+  case bitc::ATTR_KIND_NOOUTLINE:
+    return Attribute::NoOutline;
   }
 }
 

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -956,6 +956,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
     return bitc::ATTR_KIND_NO_CREATE_UNDEF_OR_POISON;
   case Attribute::DenormalFPEnv:
     return bitc::ATTR_KIND_DENORMAL_FPENV;
+  case Attribute::NoOutline:
+    return bitc::ATTR_KIND_NOOUTLINE;
   case Attribute::EndAttrKinds:
     llvm_unreachable("Can not encode end-attribute kinds marker.");
   case Attribute::None:

llvm/lib/CodeGen/MachineOutliner.cpp

@@ -1255,7 +1255,7 @@ void MachineOutliner::populateMapper(InstructionMapper &Mapper, Module &M) {
   for (Function &F : M) {
     LLVM_DEBUG(dbgs() << "MAPPING FUNCTION: " << F.getName() << "\n");
 
-    if (F.hasFnAttribute("nooutline")) {
+    if (F.hasFnAttribute(Attribute::NoOutline)) {
       LLVM_DEBUG(dbgs() << "SKIP: Function has nooutline attribute\n");
       continue;
     }

llvm/lib/IR/AutoUpgrade.cpp

@@ -6345,6 +6345,13 @@ void llvm::UpgradeFunctionAttributes(Function &F) {
     RemovingAttrs = true;
   }
 
+  if (Attribute A = F.getFnAttribute("nooutline");
+      A.isValid() && A.isStringAttribute()) {
+    AttrsToRemove.addAttribute("nooutline");
+    AttrsToAdd.addAttribute(Attribute::NoOutline);
+    AddingAttrs = RemovingAttrs = true;
+  }
+
   if (!F.empty()) {
     // For some reason this is called twice, and the first time is before any
     // instructions are loaded into the body.

llvm/lib/Transforms/IPO/IROutliner.cpp

@@ -2411,7 +2411,7 @@ void IROutliner::pruneIncompatibleRegions(
     if (FnForCurrCand.hasOptNone())
       continue;
 
-    if (FnForCurrCand.hasFnAttribute("nooutline")) {
+    if (FnForCurrCand.hasFnAttribute(Attribute::NoOutline)) {
       LLVM_DEBUG({
         dbgs() << "... Skipping function with nooutline attribute: "
                << FnForCurrCand.getName() << "\n";

llvm/lib/Transforms/Utils/CodeExtractor.cpp

@@ -949,6 +949,7 @@ Function *CodeExtractor::constructFunctionDeclaration(
       case Attribute::NoFree:
       case Attribute::NoImplicitFloat:
       case Attribute::NoInline:
+      case Attribute::NoOutline:
       case Attribute::NonLazyBind:
       case Attribute::NoRedZone:
       case Attribute::NoUnwind:

llvm/test/Bitcode/upgrade-nooutline.ll

@@ -0,0 +1,10 @@
+; RUN: llvm-as < %s | llvm-dis - | FileCheck %s --implicit-check-not='"nooutline"'
+
+; CHECK: define void @f() [[ATTR:#[0-9]+]]
+; CHECK: attributes [[ATTR]] = {
+; CHECK-SAME: nooutline
+; CHECK-SAME: }
+
+define void @f() "nooutline" {
+  ret void
+}

llvm/test/CodeGen/AArch64/machine-outliner-mapper-debug-output.mir

@@ -17,7 +17,7 @@
 
 --- |
   define void @block_too_small() noredzone { unreachable }
-  define void @no_outline() noredzone "nooutline" { unreachable }
+  define void @no_outline() noredzone nooutline { unreachable }
   define void @redzone() { unreachable }
   declare void @no_mf()
   define void @block_addr_fn() noredzone {

llvm/test/Transforms/IROutliner/nooutline-attribute.ll

@@ -8,7 +8,7 @@
 
 define void @outlinable() { ret void }
 
-define i8 @nooutline1(ptr noalias %s, ptr noalias %d, i64 %len) "nooutline" {
+define i8 @nooutline1(ptr noalias %s, ptr noalias %d, i64 %len) nooutline {
   %a = load i8, ptr %s
   %b = load i8, ptr %d
   call void @llvm.memcpy.p0.p0.i64(ptr %d, ptr %s, i64 %len, i1 false)
@@ -17,7 +17,7 @@ define i8 @nooutline1(ptr noalias %s, ptr noalias %d, i64 %len) "nooutline" {
   ret i8 %ret
 }
 
-define i8 @nooutline2(ptr noalias %s, ptr noalias %d, i64 %len) "nooutline" {
+define i8 @nooutline2(ptr noalias %s, ptr noalias %d, i64 %len) nooutline {
   %a = load i8, ptr %s
   %b = load i8, ptr %d
   call void @llvm.memcpy.p0.p0.i64(ptr %d, ptr %s, i64 %len, i1 false)

llvm/utils/kate/llvm.xml

@@ -105,6 +105,7 @@
       <item> noimplicitfloat </item>
       <item> noinline </item>
       <item> nomerge </item>
+      <item> nooutline </item>
       <item> noprofile </item>
       <item> noredzone </item>
       <item> noreturn </item>

llvm/utils/vim/syntax/llvm.vim

@@ -133,6 +133,7 @@ syn keyword llvmKeyword
       \ noimplicitfloat
       \ noinline
       \ nomerge
+      \ nooutline
       \ nonlazybind
       \ nonnull
       \ noprofile

llvm/utils/vscode/llvm/syntaxes/ll.tmLanguage.yaml

@@ -230,6 +230,7 @@ patterns:
             \\bnoimplicitfloat\\b|\
             \\bnoinline\\b|\
             \\bnomerge\\b|\
+            \\bnooutline\\b|\
             \\bnonlazybind\\b|\
             \\bnonnull\\b|\
             \\bnoprofile\\b|\