[lld] [lld-macho][arm64] implement -objc_stubs_small (PR #78665)

[Ellis Hoag via llvm-commits]

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+# REQUIRES: aarch64
+
+# RUN: llvm-mc -filetype=obj -triple=arm64-apple-darwin %s -o %t.o
+# RUN: %lld -arch arm64 -lSystem -U _objc_msgSend -o %t.out %t.o
+# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out | FileCheck %s
+# RUN: %lld -arch arm64 -lSystem -U _objc_msgSend -o %t.out %t.o -dead_strip
+# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out | FileCheck %s
+# RUN: %lld -arch arm64 -lSystem -U _objc_msgSend -o %t.out %t.o -objc_stubs_fast
+# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out | FileCheck %s
+# RUN: %lld -arch arm64 -lSystem -U _objc_msgSend -o %t.out %t.o -objc_stubs_small
+# RUN: llvm-otool -vs __TEXT __stubs  %t.out | FileCheck %s --check-prefix=STUB
+# RUN: llvm-otool -vs __TEXT __objc_stubs %t.out | FileCheck %s --check-prefix=SMALL
+
+# Unlike arm64-objc-stubs.s, in this test, _objc_msgSend is not defined,
+#  which usually binds with libobjc.dylib.
+# 1. -objc_stubs_fast: No change as it uses GOT.
+# 2. -objc_stubs_small: Create a (shared) stub to invoke _objc_msgSend, to minimize the size.
+
+# CHECK: Contents of (__TEXT,__objc_stubs) section
+
+# CHECK-NEXT: _objc_msgSend$foo:
+# CHECK-NEXT: adrp    x1, 8 ; 0x100008000
+# CHECK-NEXT: ldr     x1, [x1, #0x10]
+# CHECK-NEXT: adrp    x16, 4 ; 0x100004000
+# CHECK-NEXT: ldr     x16, [x16]
+# CHECK-NEXT: br      x16
+# CHECK-NEXT: brk     #0x1
+# CHECK-NEXT: brk     #0x1
+# CHECK-NEXT: brk     #0x1
+
+# CHECK-NEXT: _objc_msgSend$length:
+# CHECK-NEXT: adrp    x1, 8 ; 0x100008000
+# CHECK-NEXT: ldr     x1, [x1, #0x18]
+# CHECK-NEXT: adrp    x16, 4 ; 0x100004000
+# CHECK-NEXT: ldr     x16, [x16]
+# CHECK-NEXT: br      x16
+# CHECK-NEXT: brk     #0x1
+# CHECK-NEXT: brk     #0x1
+# CHECK-NEXT: brk     #0x1
+
+# CHECK-EMPTY:
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ellishg wrote:

I don't see `CHECK-EMPTY` in any filecheck command. Is this needed?

https://github.com/llvm/llvm-project/pull/78665