llvm-project

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# REQUIRES: x86
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## This test checks that when we coalesce weak definitions, their local symbol
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## aliases defs don't cause the coalesced data to be retained. This was
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## motivated by MC's aarch64 backend which automatically creates `ltmp<N>`
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## symbols at the start of each .text section. These symbols are frequently
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## aliases of other symbols created by clang or other inputs to MC. I've chosen
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## to explicitly create them here since we can then reference those symbols for
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## a more complete test.
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##
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## Not retaining the data matters for more than just size -- we have a use case
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## that depends on proper data coalescing to emit a valid file format. We also
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## need this behavior to properly deduplicate the __objc_protolist section;
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## failure to do this can result in dyld crashing on iOS 13.
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##
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## Finally, ld64 does all this regardless of whether .subsections_via_symbols is
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## specified. We don't. But again, given how rare the lack of that directive is
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## (I've only seen it from hand-written assembly inputs), I don't think we need
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## to worry about it.
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# RUN: rm -rf %t; split-file %s %t
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/weak-then-local.s -o %t/weak-then-local.o
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/local-then-weak.s -o %t/local-then-weak.o
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/no-subsections.s -o %t/no-subsections.o
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/no-dead-strip.s -o %t/no-dead-strip.o
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# RUN: %lld -lSystem -dylib %t/weak-then-local.o %t/local-then-weak.o -o %t/test1
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# RUN: llvm-objdump --macho --syms --section="__DATA,__data" --weak-bind %t/test1 | FileCheck %s
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# RUN: %lld -lSystem -dylib %t/local-then-weak.o %t/weak-then-local.o -o %t/test2
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# RUN: llvm-objdump --macho --syms --section="__DATA,__data" --weak-bind %t/test2 | FileCheck %s
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## Check that we only have one copy of 0x123 in the data, not two.
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# CHECK:       Contents of (__DATA,__data) section
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# CHECK-NEXT:  0000000000001000  23 01 00 00 00 00 00 00 00 10 00 00 00 00 00 00 {{$}}
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# CHECK-NEXT:  0000000000001010  00 10 00 00 00 00 00 00 {{$}}
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# CHECK-EMPTY:
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# CHECK-NEXT:  SYMBOL TABLE:
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# CHECK-NEXT:  0000000000001000 l     O __DATA,__data _alias
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# CHECK-NEXT:  0000000000001008 l     O __DATA,__data _ref
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# CHECK-NEXT:  0000000000001000 l     O __DATA,__data _alias
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# CHECK-NEXT:  0000000000001010 l     O __DATA,__data _ref
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# CHECK-NEXT:  0000000000001000  w    O __DATA,__data _weak
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# CHECK-NEXT:  0000000000000000         *UND* dyld_stub_binder
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# CHECK-EMPTY:
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## Even though the references were to the non-weak `_alias` symbols, ld64 still
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## emits weak binds as if they were the `_weak` symbol itself. We do not. I
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## don't know of any programs that rely on this behavior, so I'm just
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## documenting it here.
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# CHECK-NEXT:  Weak bind table:
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# CHECK-NEXT:  segment  section            address     type       addend   symbol
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# CHECK-EMPTY:
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# RUN: %lld -lSystem -dylib %t/local-then-weak.o %t/no-subsections.o -o %t/sub-nosub
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# RUN: llvm-objdump --macho --syms --section="__DATA,__data" %t/sub-nosub | FileCheck %s --check-prefix SUB-NOSUB
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## This test case demonstrates a shortcoming of LLD: If .subsections_via_symbols
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## isn't enabled, we don't elide the contents of coalesced weak symbols if they
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## are part of a section that has other non-coalesced symbols. In contrast, LD64
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## does elide the contents.
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# SUB-NOSUB:       Contents of (__DATA,__data) section
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# SUB-NOSUB-NEXT:  0000000000001000    23 01 00 00 00 00 00 00 00 10 00 00 00 00 00 00
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# SUB-NOSUB-NEXT:  0000000000001010    00 00 00 00 00 00 00 00 23 01 00 00 00 00 00 00
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# SUB-NOSUB-EMPTY:
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# SUB-NOSUB-NEXT:  SYMBOL TABLE:
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# SUB-NOSUB-NEXT:  0000000000001000 l     O __DATA,__data _alias
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# SUB-NOSUB-NEXT:  0000000000001008 l     O __DATA,__data _ref
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# SUB-NOSUB-NEXT:  0000000000001010 l     O __DATA,__data _zeros
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# SUB-NOSUB-NEXT:  0000000000001000 l     O __DATA,__data _alias
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# SUB-NOSUB-NEXT:  0000000000001000  w    O __DATA,__data _weak
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# SUB-NOSUB-NEXT:  0000000000000000         *UND* dyld_stub_binder
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# RUN: %lld -lSystem -dylib %t/no-subsections.o %t/local-then-weak.o -o %t/nosub-sub
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# RUN: llvm-objdump --macho --syms --section="__DATA,__data" %t/nosub-sub | FileCheck %s --check-prefix NOSUB-SUB
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# NOSUB-SUB:       Contents of (__DATA,__data) section
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# NOSUB-SUB-NEXT:  0000000000001000    00 00 00 00 00 00 00 00 23 01 00 00 00 00 00 00
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# NOSUB-SUB-NEXT:  0000000000001010    08 10 00 00 00 00 00 00 {{$}}
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# NOSUB-SUB-EMPTY:
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# NOSUB-SUB-NEXT:  SYMBOL TABLE:
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# NOSUB-SUB-NEXT:  0000000000001000 l     O __DATA,__data _zeros
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# NOSUB-SUB-NEXT:  0000000000001008 l     O __DATA,__data _alias
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# NOSUB-SUB-NEXT:  0000000000001008 l     O __DATA,__data _alias
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# NOSUB-SUB-NEXT:  0000000000001010 l     O __DATA,__data _ref
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# NOSUB-SUB-NEXT:  0000000000001008  w    O __DATA,__data _weak
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# NOSUB-SUB-NEXT:  0000000000000000         *UND* dyld_stub_binder
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## Verify that we don't drop any flags that the aliases have (such as
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## .no_dead_strip). This is a regression test. We previously had subsections
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## that were mistakenly stripped.
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# RUN: %lld -lSystem -dead_strip %t/no-dead-strip.o -o %t/no-dead-strip
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# RUN: llvm-objdump --macho --section-headers %t/no-dead-strip | FileCheck %s \
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# RUN:   --check-prefix=NO-DEAD-STRIP
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# NO-DEAD-STRIP: __data        00000010
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#--- weak-then-local.s
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.globl _weak
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.weak_definition _weak
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.data
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_weak:
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_alias:
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  .quad 0x123
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_ref:
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  .quad _alias
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.subsections_via_symbols
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#--- local-then-weak.s
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.globl _weak
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.weak_definition _weak
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.data
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_alias:
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_weak:
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  .quad 0x123
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_ref:
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  .quad _alias
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.subsections_via_symbols
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#--- no-subsections.s
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.globl _weak
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.weak_definition _weak
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.data
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_zeros:
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.space 8
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_weak:
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_alias:
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  .quad 0x123
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#--- no-dead-strip.s
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.globl _main
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_main:
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  ret
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.data
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.no_dead_strip l_foo, l_bar
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_foo:
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l_foo:
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  .quad 0x123
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l_bar:
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_bar:
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  .quad 0x123
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.subsections_via_symbols
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