[lld-macho] Fix __objc_stubs ordering

[keith]

Summary

In the case of large binaries previously you could end up getting
relocation failures. This mirrors ld64's ordering of these sections. I'm
not sure this solves all cases but it should help in some.

Fixes https://github.com/llvm/llvm-project/issues/58298

[keith]

Fix test addrs

[int3]

Thanks!

lld/test/MachO/x86-64-objc-stubs.s

24–28

Ideally the test would've been written using substitutions instead of hardcoded addresses so we don't have this churn. It would probably also make the test more comprehensive. See start-end.s line 102 for an example of how to test RIP-relative addresses. I'm fine with this being done in some future commit though :)

[keith]

Make tests address independent

[keith]

lld/test/MachO/x86-64-objc-stubs.s

24–28

Updated these and verified they passed before and after. because of that maybe they're a bit less strict than they could be

lld/MachO/OutputSegment.cpp

return StringSwitch<int>(seg->name)
       .Default(seg->inputOrder);
 }
 
 static int sectionOrder(OutputSection *osec) {
   StringRef segname = osec->parent->name;
   // Sections are uniquely identified by their segment + section name.
   if (segname == segment_names::text) {
     return StringSwitch<int>(osec->name)
-        .Case(section_names::header, -5)
-        .Case(section_names::text, -4)
-        .Case(section_names::stubs, -3)
-        .Case(section_names::stubHelper, -2)
+        .Case(section_names::header, -6)
+        .Case(section_names::text, -5)
+        .Case(section_names::stubs, -4)
+        .Case(section_names::stubHelper, -3)
+        .Case(section_names::objcStubs, -2)
         .Case(section_names::initOffsets, -1)
         .Case(section_names::unwindInfo, std::numeric_limits<int>::max() - 1)
         .Case(section_names::ehFrame, std::numeric_limits<int>::max())
         .Default(osec->inputOrder);
   } else if (segname == segment_names::data ||
              segname == segment_names::dataConst) {
     // For each thread spawned, dyld will initialize its TLVs by copying the
     // address range from the start of the first thread-local data section to

lld/test/MachO/x86-64-objc-stubs.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
 # RUN: %lld -arch x86_64 -lSystem -o %t.out %t.o
-# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out | FileCheck %s
+# RUN: llvm-objdump --macho --section-headers %t.out > %t.txt
+# RUN: llvm-otool -vs __DATA __objc_selrefs %t.out >> %t.txt
+# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out >> %t.txt
+# RUN: FileCheck %s < %t.txt
+
+# CHECK: Sections:
+# CHECK: __got            {{[0-9a-f]*}} [[#%x, GOTSTART:]] DATA
+# CHECK: __objc_selrefs   {{[0-9a-f]*}} [[#%x, SELSTART:]] DATA
+
+# CHECK: Contents of (__DATA,__objc_selrefs) section
+
+# CHECK-NEXT: {{[0-9a-f]*}}  __TEXT:__objc_methname:foo
+# CHECK-NEXT: {{[0-9a-f]*}}  __TEXT:__objc_methname:bar
+# CHECK-NEXT: [[#%x, FOOSELREF:]]  __TEXT:__objc_methname:foo
+# CHECK-NEXT: [[#%x, LENGTHSELREF:]]  __TEXT:__objc_methname:length
 
 # CHECK: Contents of (__TEXT,__objc_stubs) section
 
 # CHECK-NEXT: _objc_msgSend$foo:
-# CHECK-NEXT: 00000001000004b8  movq  0x1b51(%rip), %rsi
-# CHECK-NEXT: 00000001000004bf  jmpq  *0xb3b(%rip)
+# CHECK-NEXT: [[#%x, PC1:]]
+# CHECK-SAME: movq    0x[[#%x, FOOSELREF - PC1 - 7]](%rip), %rsi
+# CHECK-NEXT: [[#%x, PC2:]]
+# CHECK-SAME: jmpq    *0x[[#%x, GOTSTART - PC2 - 6]](%rip)
 
 # CHECK-NEXT: _objc_msgSend$length:
-# CHECK-NEXT: 00000001000004c5  movq  0x1b4c(%rip), %rsi
-# CHECK-NEXT: 00000001000004cc  jmpq  *0xb2e(%rip)
+# CHECK-NEXT: [[#%x, PC3:]]
+# CHECK-SAME: movq    0x[[#%x, LENGTHSELREF - PC3 - 7]](%rip), %rsi
+# CHECK-NEXT: [[#%x, PC4:]]
+# CHECK-SAME: jmpq    *0x[[#%x, GOTSTART - PC4 - 6]](%rip)
 
 # CHECK-EMPTY:
 
 .section  __TEXT,__objc_methname,cstring_literals
 lselref1:
   .asciz  "foo"
 lselref2:
   .asciz  "bar"