[ORC] Loosen __objc_imageinfo flag merging to match ld (#91767)

Allow mixing objects with/without signed class ro data and category
class properties as long as it happens before we register the metadata.
These combinations are a warning in ld, not a hard error. The only case
that is ABI-breaking is if we already registered with the feature
enabled but later try to load an object that doesn't support it.

rdar://127336061

Author: benlangmuir

compiler-rt/test/orc/TestCases/Darwin/arm64/objc-imageinfo.S

@@ -27,9 +27,6 @@
 
 // Check error conditions.
 
-// RUN: not %llvm_jitlink %t/main.o %t/objc_old.o %t/objc_new.o 2>&1 | FileCheck %s -check-prefix=CATEGORY
-// CATEGORY: ObjC category class property support in {{.*}} does not match first registered flags
-
 // RUN: not %llvm_jitlink %t/main.o %t/swift_4.o %t/swift_5.o 2>&1 | FileCheck %s -check-prefix=SWIFT_ABI
 // SWIFT_ABI: Swift ABI version in {{.*}} does not match first registered flags
 
@@ -47,6 +44,14 @@
 // RUN: %llvm_jitlink -debug-only=orc %t/main.o %t/swift_59.o %t/swift_5.o %t/objc_new.o 2>&1 | FileCheck %s -check-prefix=SWIFT_MIX3
 // SWIFT_MIX3: MachOPlatform: Merging __objc_imageinfo flags for main {{.*}} -> 0x5000740
 
+// Disable categories.
+// RUN: %llvm_jitlink -debug-only=orc %t/main.o %t/objc_old.o %t/objc_new.o 2>&1 | FileCheck %s -check-prefix=SWIFT_MIX4
+// SWIFT_MIX4: MachOPlatform: Merging __objc_imageinfo flags for main {{.*}} -> 0x0000
+
+// Disable signed class_ro.
+// RUN: %llvm_jitlink -debug-only=orc %t/main.o %t/objc_new.o %t/objc_new_signed_ro.o 2>&1 | FileCheck %s -check-prefix=SWIFT_MIX5
+// SWIFT_MIX5: MachOPlatform: Merging __objc_imageinfo flags for main {{.*}} -> 0x0040
+
 //--- main.S
 .section  __TEXT,__text,regular,pure_instructions
 .globl _main
@@ -76,6 +81,17 @@ L_OBJC_IMAGE_INFO:
   .long 0
   .long 64
 
+//--- objc_new_signed_ro.S
+.section  __TEXT,__text,regular,pure_instructions
+.globl _objc3
+_objc3:
+  ret
+
+  .section  __DATA,__objc_imageinfo,regular,no_dead_strip
+L_OBJC_IMAGE_INFO:
+  .long 0
+  .long 80
+
 //--- swift_4.S
 .section  __TEXT,__text,regular,pure_instructions
 .globl _swift4

compiler-rt/test/orc/TestCases/Darwin/x86-64/objc-imageinfo.S

@@ -27,9 +27,6 @@
 
 // Check error conditions.
 
-// RUN: not %llvm_jitlink %t/main.o %t/objc_old.o %t/objc_new.o 2>&1 | FileCheck %s -check-prefix=CATEGORY
-// CATEGORY: ObjC category class property support in {{.*}} does not match first registered flags
-
 // RUN: not %llvm_jitlink %t/main.o %t/swift_4.o %t/swift_5.o 2>&1 | FileCheck %s -check-prefix=SWIFT_ABI
 // SWIFT_ABI: Swift ABI version in {{.*}} does not match first registered flags
 
@@ -47,6 +44,14 @@
 // RUN: %llvm_jitlink -debug-only=orc %t/main.o %t/swift_59.o %t/swift_5.o %t/objc_new.o 2>&1 | FileCheck %s -check-prefix=SWIFT_MIX3
 // SWIFT_MIX3: MachOPlatform: Merging __objc_imageinfo flags for main {{.*}} -> 0x5000740
 
+// Disable categories.
+// RUN: %llvm_jitlink -debug-only=orc %t/main.o %t/objc_old.o %t/objc_new.o 2>&1 | FileCheck %s -check-prefix=SWIFT_MIX4
+// SWIFT_MIX4: MachOPlatform: Merging __objc_imageinfo flags for main {{.*}} -> 0x0000
+
+// Disable signed class_ro.
+// RUN: %llvm_jitlink -debug-only=orc %t/main.o %t/objc_new.o %t/objc_new_signed_ro.o 2>&1 | FileCheck %s -check-prefix=SWIFT_MIX5
+// SWIFT_MIX5: MachOPlatform: Merging __objc_imageinfo flags for main {{.*}} -> 0x0040
+
 //--- main.S
 .section  __TEXT,__text,regular,pure_instructions
 .globl _main
@@ -76,6 +81,17 @@ L_OBJC_IMAGE_INFO:
   .long 0
   .long 64
 
+//--- objc_new_signed_ro.S
+.section  __TEXT,__text,regular,pure_instructions
+.globl _objc3
+_objc3:
+  ret
+
+  .section  __DATA,__objc_imageinfo,regular,no_dead_strip
+L_OBJC_IMAGE_INFO:
+  .long 0
+  .long 80
+
 //--- swift_4.S
 .section  __TEXT,__text,regular,pure_instructions
 .globl _swift4

llvm/lib/ExecutionEngine/Orc/MachOPlatform.cpp

@@ -1134,12 +1134,16 @@ Error MachOPlatform::MachOPlatformPlugin::mergeImageInfoFlags(
                                        " does not match first registered flags",
                                    inconvertibleErrorCode());
 
-  if (Old.HasCategoryClassProperties != New.HasCategoryClassProperties)
+  // HasCategoryClassProperties and HasSignedObjCClassROs can be disabled before
+  // they are registered, if necessary, but once they are in use must be
+  // supported by subsequent objects.
+  if (Info.Finalized && Old.HasCategoryClassProperties &&
+      !New.HasCategoryClassProperties)
     return make_error<StringError>("ObjC category class property support in " +
                                        G.getName() +
                                        " does not match first registered flags",
                                    inconvertibleErrorCode());
-  if (Old.HasSignedObjCClassROs != New.HasSignedObjCClassROs)
+  if (Info.Finalized && Old.HasSignedObjCClassROs && !New.HasSignedObjCClassROs)
     return make_error<StringError>("ObjC class_ro_t pointer signing in " +
                                        G.getName() +
                                        " does not match first registered flags",
@@ -1158,6 +1162,12 @@ Error MachOPlatform::MachOPlatformPlugin::mergeImageInfoFlags(
   // Add a Swift ABI version if it was pure objc before.
   if (!New.SwiftABIVersion)
     New.SwiftABIVersion = Old.SwiftABIVersion;
+  // Disable class properties if any object does not support it.
+  if (Old.HasCategoryClassProperties != New.HasCategoryClassProperties)
+    New.HasCategoryClassProperties = false;
+  // Disable signed class ro data if any object does not support it.
+  if (Old.HasSignedObjCClassROs != New.HasSignedObjCClassROs)
+    New.HasSignedObjCClassROs = false;
 
   LLVM_DEBUG({
     dbgs() << "MachOPlatform: Merging __objc_imageinfo flags for "