[lld-macho][nfc] Test that -ObjC will import bitcode with category sections

[int3]

Summary

The functionality was originally added in D95265: [lld-macho] Force-loading should share code path with regular archive loads, but the test in that
diff only checked if -ObjC would cause bitcode containing ObjC class
symbols to be loaded. It neglected to test for bitcode containing
categories but no class symbols.

This diff also changes the lto-archive.ll test to use -why_load
instead of inspecting the output binary's symbol table. This is
motivated by the stacked diff D99105: [lld-macho] LTO: Unset VisibleToRegularObj where possible, which will hide irrelevant
bitcode symbols.

[int3]

bump

[oontvoo]

Looks fairly straightforward to me

lld/test/MachO/lto-archive.ll

 ; REQUIRES: x86
 ; RUN: rm -rf %t; split-file %s %t
 ; RUN: llvm-as %t/foo.ll -o %t/foo.o
-; RUN: llvm-as %t/objc.ll -o %t/objc.o
+; RUN: llvm-as %t/has-objc-symbol.ll -o %t/has-objc-symbol.o
+; RUN: llvm-as %t/has-objc-category.ll -o %t/has-objc-category.o
 ; RUN: llvm-ar rcs %t/foo.a %t/foo.o
-; RUN: llvm-ar rcs %t/objc.a %t/objc.o
+; RUN: llvm-ar rcs %t/objc.a %t/has-objc-symbol.o %t/has-objc-category.o
 
 ; RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/main.s -o %t/main.o
 ; RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/references-foo.s -o %t/references-foo.o
 
-; RUN: %lld -lSystem %t/references-foo.o %t/foo.a -o %t/test
-; RUN: llvm-objdump --macho --syms %t/test | FileCheck %s --check-prefix=FOO
+; RUN: %lld -lSystem %t/references-foo.o %t/foo.a -o /dev/null -why_load | FileCheck %s --check-prefix=FOO
+; FOO: _foo forced load of foo.o
 
-; RUN: %lld -lSystem -force_load %t/foo.a %t/main.o -o %t/force-load
-; RUN: llvm-objdump --macho --syms %t/force-load | FileCheck %s --check-prefix=FOO
+; RUN: %lld -lSystem -force_load %t/foo.a %t/main.o -o /dev/null -why_load | FileCheck %s --check-prefix=FORCE-LOAD
+; FORCE-LOAD: -force_load forced load of foo.o
 
-; RUN: %lld -lSystem %t/foo.a %t/main.o -o %t/no-force-load
-; RUN: llvm-objdump --macho --syms %t/no-force-load | FileCheck %s --check-prefix=NO-FOO
+; RUN: %lld -lSystem -ObjC -framework CoreFoundation %t/objc.a %t/main.o \
+; RUN:   -o /dev/null -why_load | FileCheck %s --check-prefix=OBJC
+; OBJC: -ObjC forced load of has-objc-category.o
+; OBJC: _OBJC_CLASS_$_Foo forced load of has-objc-symbol.o
 
-; RUN: %lld -lSystem -ObjC -framework CoreFoundation %t/objc.a %t/main.o -o %t/objc
-; RUN: llvm-objdump --macho --syms %t/objc | FileCheck %s --check-prefix=OBJC
+; RUN: %lld -lSystem %t/foo.a %t/main.o -o %t/no-force-load -why_load | \
+; RUN:   FileCheck %s --allow-empty --check-prefix=NO-LOAD
 
-; RUN: %lld -lSystem -framework CoreFoundation %t/objc.a %t/main.o -o %t/no-objc
-; RUN: llvm-objdump --macho --syms %t/no-objc | FileCheck %s --check-prefix=NO-OBJC
+; RUN: %lld -lSystem -framework CoreFoundation %t/objc.a %t/main.o -o %t/no-objc -why_load | \
+; RUN:   FileCheck %s --allow-empty --check-prefix=NO-LOAD
 
-; FOO: _foo
-
-; NO-FOO-NOT: _foo
-
-; OBJC-DAG: _OBJC_CLASS_$_Foo
-; OBJC-DAG: _OBJC_METACLASS_$_Foo
-
-; NO-OBJC-NOT: _OBJC_CLASS_$_Foo
-; NO-OBJC-NOT: _OBJC_METACLASS_$_Foo
+; NO-LOAD-NOT: forced load
 
 ;--- foo.ll
 
 target triple = "x86_64-apple-macosx10.15.0"
 target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @foo() {
   ret void
 }
 
-;--- objc.ll
+;--- has-objc-symbol.ll
 
 target triple = "x86_64-apple-macosx10.15.0"
 target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 
-%struct._class_t = type { %struct._class_t*, %struct._class_t*, %struct._class_ro_t* }
-%struct._class_ro_t = type { i8* }
+%struct._class_t = type { i8 }
+@"OBJC_CLASS_$_Foo" = global %struct._class_t { i8 123 }
+
+;--- has-objc-category.ll
+
+target triple = "x86_64-apple-macosx10.15.0"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+%struct._category_t = type { i8 }
+
+@"_OBJC_$_CATEGORY_Foo_$_Bar" = internal global %struct._category_t { i8 123 },
+  section "__DATA, __objc_const", align 8
 
-@"OBJC_METACLASS_$_NSObject" = external global %struct._class_t
-@OBJC_CLASS_NAME_ = private unnamed_addr constant [4 x i8] c"Foo\00",
-  section "__TEXT,__objc_classname,cstring_literals"
-@"_OBJC_METACLASS_RO_$_Foo" = internal global %struct._class_ro_t {
-    i8* getelementptr inbounds ([4 x i8], [4 x i8]* @OBJC_CLASS_NAME_, i32 0, i32 0)
-  },
-  section "__DATA, __objc_const"
-@"OBJC_METACLASS_$_Foo" = global %struct._class_t {
-    %struct._class_t* @"OBJC_METACLASS_$_NSObject",
-    %struct._class_t* @"OBJC_METACLASS_$_NSObject",
-    %struct._class_ro_t* @"_OBJC_METACLASS_RO_$_Foo"
-  },
-  section "__DATA, __objc_data"
-@"OBJC_CLASS_$_NSObject" = external global %struct._class_t
-@"_OBJC_CLASS_RO_$_Foo" = internal global %struct._class_ro_t {
-    i8* getelementptr inbounds ([4 x i8], [4 x i8]* @OBJC_CLASS_NAME_, i32 0, i32 0)
-  },
-  section "__DATA, __objc_const"
-@"OBJC_CLASS_$_Foo" = global %struct._class_t {
-    %struct._class_t* @"OBJC_METACLASS_$_Foo",
-    %struct._class_t* @"OBJC_CLASS_$_NSObject",
-    %struct._class_ro_t* @"_OBJC_CLASS_RO_$_Foo"
-  },
-  section "__DATA, __objc_data"
+@"OBJC_LABEL_CATEGORY_$" = private global [1 x i8*] [
+  i8* bitcast (%struct._category_t* @"_OBJC_$_CATEGORY_Foo_$_Bar" to i8*)
+  ], section "__DATA,__objc_catlist,regular,no_dead_strip", align 8
+
[e-mail] = appending global [1 x i8*] [
+  i8* bitcast ([1 x i8*]* @"OBJC_LABEL_CATEGORY_$" to i8*)
+  ], section "llvm.metadata"
 
 ;--- main.s
 
 .globl _main
 _main:
   ret
 
 ;--- references-foo.s
 
 .globl _main
 _main:
   callq _foo
   ret