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llvm-project/lld/test/MachO/dead-strip.s

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[lld/mac] Implement -dead_strip Also adds support for live_support sections, no_dead_strip sections, .no_dead_strip symbols. Chromium Framework 345MB unstripped -> 250MB stripped (vs 290MB unstripped -> 236M stripped with ld64). Doing dead stripping is a bit faster than not, because so much less data needs to be processed: % ministat lld_* x lld_nostrip.txt + lld_strip.txt N Min Max Median Avg Stddev x 10 3.929414 4.07692 4.0269079 4.0089678 0.044214794 + 10 3.8129408 3.9025559 3.8670411 3.8642573 0.024779651 Difference at 95.0% confidence -0.144711 +/- 0.0336749 -3.60967% +/- 0.839989% (Student's t, pooled s = 0.0358398) This interacts with many parts of the linker. I tried to add test coverage for all added `isLive()` checks, so that some test will fail if any of them is removed. I checked that the test expectations for the most part match ld64's behavior (except for live-support-iterations.s, see the comment in the test). Interacts with: - debug info - export tries - import opcodes - flags like -exported_symbol(s_list) - -U / dynamic_lookup - mod_init_funcs, mod_term_funcs - weak symbol handling - unwind info - stubs - map files - -sectcreate - undefined, dylib, common, defined (both absolute and normal) symbols It's possible it interacts with more features I didn't think of, of course. I also did some manual testing: - check-llvm check-clang check-lld work with lld with this patch as host linker and -dead_strip enabled - Chromium still starts - Chromium's base_unittests still pass, including unwind tests Implemenation-wise, this is InputSection-based, so it'll work for object files with .subsections_via_symbols (which includes all object files generated by clang). I first based this on the COFF implementation, but later realized that things are more similar to ELF. I think it'd be good to refactor MarkLive.cpp to look more like the ELF part at some point, but I'd like to get a working state checked in first. Mechanical parts: - Rename canOmitFromOutput to wasCoalesced (no behavior change) since it really is for weak coalesced symbols - Add noDeadStrip to Defined, corresponding to N_NO_DEAD_STRIP (`.no_dead_strip` in asm) Fixes PR49276. Differential Revision: https://reviews.llvm.org/D103324
2021-05-08 05:10:05 +08:00
# REQUIRES: x86
# RUN: rm -rf %t; split-file %s %t
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/basics.s -o %t/basics.o
## Check that .private_extern symbols are marked as local in the symbol table
## and aren't in the export trie.
## Dead-stripped symbols should also not be in a map file output.
# RUN: %lld -lSystem -dead_strip -map %t/map -u _ref_private_extern_u \
# RUN: %t/basics.o -o %t/basics
# RUN: llvm-objdump --syms --section-headers %t/basics | \
# RUN: FileCheck --check-prefix=EXEC --implicit-check-not _unref %s
# RUN: llvm-objdump --macho --section=__DATA,__ref_section \
# RUN: --exports-trie --indirect-symbols %t/basics | \
# RUN: FileCheck --check-prefix=EXECDATA --implicit-check-not _unref %s
# RUN: llvm-otool -l %t/basics | grep -q 'segname __PAGEZERO'
# RUN: FileCheck --check-prefix=MAP --implicit-check-not _unref %s < %t/map
# EXEC-LABEL: Sections:
# EXEC-LABEL: Name
# EXEC-NEXT: __text
# EXEC-NEXT: __got
# EXEC-NEXT: __ref_section
# EXEC-NEXT: __common
# EXEC-LABEL: SYMBOL TABLE:
# EXEC-NEXT: l {{.*}} _ref_data
# EXEC-NEXT: l {{.*}} _ref_local
# EXEC-NEXT: l {{.*}} _ref_from_no_dead_strip_globl
# EXEC-NEXT: l {{.*}} _no_dead_strip_local
# EXEC-NEXT: l {{.*}} _ref_from_no_dead_strip_local
# EXEC-NEXT: l {{.*}} _ref_private_extern_u
# EXEC-NEXT: l {{.*}} _main
# EXEC-NEXT: l {{.*}} _ref_private_extern
# EXEC-NEXT: g {{.*}} _ref_com
# EXEC-NEXT: g {{.*}} _no_dead_strip_globl
# EXEC-NEXT: g {{.*}} __mh_execute_header
# EXECDATA-LABEL: Indirect symbols
# EXECDATA-NEXT: name
# EXECDATA-NEXT: _ref_com
# EXECDATA-LABEL: Contents of (__DATA,__ref_section) section
# EXECDATA-NEXT: 04 00 00 00 00 00 00 00 05 00 00 00 00 00 00 00
# EXECDATA-LABEL: Exports trie:
# EXECDATA-NEXT: __mh_execute_header
# EXECDATA-NEXT: _ref_com
# EXECDATA-NEXT: _no_dead_strip_globl
# MAP: _main
# RUN: %lld -dylib -dead_strip -u _ref_private_extern_u %t/basics.o -o %t/basics.dylib
# RUN: llvm-objdump --syms %t/basics.dylib | \
# RUN: FileCheck --check-prefix=DYLIB --implicit-check-not _unref %s
# RUN: %lld -bundle -dead_strip -u _ref_private_extern_u %t/basics.o -o %t/basics.dylib
# RUN: llvm-objdump --syms %t/basics.dylib | \
# RUN: FileCheck --check-prefix=DYLIB --implicit-check-not _unref %s
# DYLIB-LABEL: SYMBOL TABLE:
# DYLIB-NEXT: l {{.*}} _ref_data
# DYLIB-NEXT: l {{.*}} _ref_local
# DYLIB-NEXT: l {{.*}} _ref_from_no_dead_strip_globl
# DYLIB-NEXT: l {{.*}} _no_dead_strip_local
# DYLIB-NEXT: l {{.*}} _ref_from_no_dead_strip_local
# DYLIB-NEXT: l {{.*}} _ref_private_extern_u
# DYLIB-NEXT: l {{.*}} _ref_private_extern
# DYLIB-NEXT: g {{.*}} _ref_com
# DYLIB-NEXT: g {{.*}} _unref_com
# DYLIB-NEXT: g {{.*}} _unref_extern
# DYLIB-NEXT: g {{.*}} _no_dead_strip_globl
## Absolute symbol handling.
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/abs.s -o %t/abs.o
# RUN: %lld -lSystem -dead_strip %t/abs.o -o %t/abs
# RUN: llvm-objdump --macho --syms --exports-trie %t/abs | \
# RUN: FileCheck --check-prefix=ABS %s
#ABS-LABEL: SYMBOL TABLE:
#ABS-NEXT: g {{.*}} _main
#ABS-NEXT: g *ABS* _abs1
#ABS-NEXT: g {{.*}} __mh_execute_header
#ABS-LABEL: Exports trie:
#ABS-NEXT: __mh_execute_header
#ABS-NEXT: _main
#ABS-NEXT: _abs1 [absolute]
## Check that symbols from -exported_symbol(s_list) are preserved.
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/exported-symbol.s -o %t/exported-symbol.o
# RUN: %lld -lSystem -dead_strip -exported_symbol _my_exported_symbol \
# RUN: %t/exported-symbol.o -o %t/exported-symbol
# RUN: llvm-objdump --syms %t/exported-symbol | \
# RUN: FileCheck --check-prefix=EXPORTEDSYMBOL --implicit-check-not _unref %s
# EXPORTEDSYMBOL-LABEL: SYMBOL TABLE:
# EXPORTEDSYMBOL-NEXT: l {{.*}} _main
# EXPORTEDSYMBOL-NEXT: l {{.*}} __mh_execute_header
# EXPORTEDSYMBOL-NEXT: g {{.*}} _my_exported_symbol
## Check that mod_init_funcs and mod_term_funcs are not stripped.
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/mod-funcs.s -o %t/mod-funcs.o
# RUN: %lld -lSystem -dead_strip %t/mod-funcs.o -o %t/mod-funcs
# RUN: llvm-objdump --syms %t/mod-funcs | \
# RUN: FileCheck --check-prefix=MODFUNCS --implicit-check-not _unref %s
# MODFUNCS-LABEL: SYMBOL TABLE:
# MODFUNCS-NEXT: l {{.*}} _ref_from_init
# MODFUNCS-NEXT: l {{.*}} _ref_init
# MODFUNCS-NEXT: l {{.*}} _ref_from_term
# MODFUNCS-NEXT: l {{.*}} _ref_term
# MODFUNCS-NEXT: g {{.*}} _main
# MODFUNCS-NEXT: g {{.*}} __mh_execute_header
## Check that DylibSymbols in dead subsections are stripped: They should
## not be in the import table and should have no import stubs.
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/dylib.s -o %t/dylib.o
# RUN: %lld -dylib -dead_strip %t/dylib.o -o %t/dylib.dylib
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/strip-dylib-ref.s -o %t/strip-dylib-ref.o
# RUN: %lld -lSystem -dead_strip %t/strip-dylib-ref.o %t/dylib.dylib \
# RUN: -o %t/strip-dylib-ref -U _ref_undef_fun -U _unref_undef_fun
# RUN: llvm-objdump --syms --bind --lazy-bind --weak-bind %t/strip-dylib-ref | \
# RUN: FileCheck --check-prefix=STRIPDYLIB --implicit-check-not _unref %s
# STRIPDYLIB: SYMBOL TABLE:
# STRIPDYLIB-NEXT: l {{.*}} __dyld_private
# STRIPDYLIB-NEXT: g {{.*}} _main
# STRIPDYLIB-NEXT: g {{.*}} __mh_execute_header
# STRIPDYLIB-NEXT: *UND* _ref_undef_fun
# STRIPDYLIB-NEXT: *UND* dyld_stub_binder
# STRIPDYLIB-NEXT: *UND* _ref_dylib_fun
# STRIPDYLIB: Bind table:
# STRIPDYLIB: Lazy bind table:
# STRIPDYLIB: __DATA __la_symbol_ptr {{.*}} flat-namespace _ref_undef_fun
# STRIPDYLIB: __DATA __la_symbol_ptr {{.*}} dylib _ref_dylib_fun
# STRIPDYLIB: Weak bind table:
## Stubs smoke check: There should be two stubs entries, not four, but we
## don't verify that they belong to _ref_undef_fun and _ref_dylib_fun.
# RUN: llvm-objdump -d --section=__stubs --section=__stub_helper \
# RUN: %t/strip-dylib-ref |FileCheck --check-prefix=STUBS %s
# STUBS-LABEL: <__stubs>:
# STUBS-NEXT: jmpq
# STUBS-NEXT: jmpq
# STUBS-NOT: jmpq
# STUBS-LABEL: <__stub_helper>:
# STUBS: pushq $0
# STUBS: jmp
# STUBS: jmp
# STUBS-NOT: jmp
## An undefined symbol referenced from a dead-stripped function shouldn't
## produce a diagnostic:
# RUN: %lld -lSystem -dead_strip %t/strip-dylib-ref.o %t/dylib.dylib \
# RUN: -o %t/strip-dylib-ref -U _ref_undef_fun
## S_ATTR_LIVE_SUPPORT tests.
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/live-support.s -o %t/live-support.o
# RUN: %lld -lSystem -dead_strip %t/live-support.o %t/dylib.dylib \
# RUN: -U _ref_undef_fun -U _unref_undef_fun -o %t/live-support
# RUN: llvm-objdump --syms %t/live-support | \
# RUN: FileCheck --check-prefix=LIVESUPP --implicit-check-not _unref %s
# LIVESUPP-LABEL: SYMBOL TABLE:
# LIVESUPP-NEXT: l {{.*}} _ref_ls_fun_fw
# LIVESUPP-NEXT: l {{.*}} _ref_ls_fun_bw
# LIVESUPP-NEXT: l {{.*}} _ref_ls_dylib_fun
# LIVESUPP-NEXT: l {{.*}} _ref_ls_undef_fun
# LIVESUPP-NEXT: l {{.*}} __dyld_private
# LIVESUPP-NEXT: g {{.*}} _main
# LIVESUPP-NEXT: g {{.*}} _bar
# LIVESUPP-NEXT: g {{.*}} _foo
# LIVESUPP-NEXT: g {{.*}} __mh_execute_header
# LIVESUPP-NEXT: *UND* _ref_undef_fun
# LIVESUPP-NEXT: *UND* dyld_stub_binder
# LIVESUPP-NEXT: *UND* _ref_dylib_fun
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/live-support-iterations.s -o %t/live-support-iterations.o
# RUN: %lld -lSystem -dead_strip %t/live-support-iterations.o \
# RUN: -o %t/live-support-iterations
# RUN: llvm-objdump --syms %t/live-support-iterations | \
# RUN: FileCheck --check-prefix=LIVESUPP2 --implicit-check-not _unref %s
# LIVESUPP2-LABEL: SYMBOL TABLE:
# LIVESUPP2-NEXT: l {{.*}} _bar
# LIVESUPP2-NEXT: l {{.*}} _foo_refd
# LIVESUPP2-NEXT: l {{.*}} _bar_refd
# LIVESUPP2-NEXT: l {{.*}} _baz
# LIVESUPP2-NEXT: l {{.*}} _baz_refd
# LIVESUPP2-NEXT: l {{.*}} _foo
# LIVESUPP2-NEXT: g {{.*}} _main
# LIVESUPP2-NEXT: g {{.*}} __mh_execute_header
## Dead stripping should not remove the __TEXT,__unwind_info
## and __TEXT,__gcc_except_tab functions, but it should still
## remove the unreferenced function __Z5unref.
## The reference to ___gxx_personality_v0 should also not be
## stripped.
## (Need to use darwin19.0.0 to make -mc emit __LD,__compact_unwind.)
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin19.0.0 \
# RUN: %t/unwind.s -o %t/unwind.o
# RUN: %lld -lc++ -lSystem -dead_strip %t/unwind.o -o %t/unwind
# RUN: llvm-objdump --syms %t/unwind | \
# RUN: FileCheck --check-prefix=UNWIND --implicit-check-not unref %s
[lld/mac] try to fix tests after a5645513dba My linux system doesn't like the `grep` for some reason, but FileCheck seems to work.
2021-06-02 23:33:08 +08:00
# RUN: llvm-otool -l %t/unwind | FileCheck --check-prefix=UNWINDSECT %s
# UNWINDSECT-DAG: sectname __unwind_info
# UNWINDSECT-DAG: sectname __gcc_except_tab
[lld/mac] Implement -dead_strip Also adds support for live_support sections, no_dead_strip sections, .no_dead_strip symbols. Chromium Framework 345MB unstripped -> 250MB stripped (vs 290MB unstripped -> 236M stripped with ld64). Doing dead stripping is a bit faster than not, because so much less data needs to be processed: % ministat lld_* x lld_nostrip.txt + lld_strip.txt N Min Max Median Avg Stddev x 10 3.929414 4.07692 4.0269079 4.0089678 0.044214794 + 10 3.8129408 3.9025559 3.8670411 3.8642573 0.024779651 Difference at 95.0% confidence -0.144711 +/- 0.0336749 -3.60967% +/- 0.839989% (Student's t, pooled s = 0.0358398) This interacts with many parts of the linker. I tried to add test coverage for all added `isLive()` checks, so that some test will fail if any of them is removed. I checked that the test expectations for the most part match ld64's behavior (except for live-support-iterations.s, see the comment in the test). Interacts with: - debug info - export tries - import opcodes - flags like -exported_symbol(s_list) - -U / dynamic_lookup - mod_init_funcs, mod_term_funcs - weak symbol handling - unwind info - stubs - map files - -sectcreate - undefined, dylib, common, defined (both absolute and normal) symbols It's possible it interacts with more features I didn't think of, of course. I also did some manual testing: - check-llvm check-clang check-lld work with lld with this patch as host linker and -dead_strip enabled - Chromium still starts - Chromium's base_unittests still pass, including unwind tests Implemenation-wise, this is InputSection-based, so it'll work for object files with .subsections_via_symbols (which includes all object files generated by clang). I first based this on the COFF implementation, but later realized that things are more similar to ELF. I think it'd be good to refactor MarkLive.cpp to look more like the ELF part at some point, but I'd like to get a working state checked in first. Mechanical parts: - Rename canOmitFromOutput to wasCoalesced (no behavior change) since it really is for weak coalesced symbols - Add noDeadStrip to Defined, corresponding to N_NO_DEAD_STRIP (`.no_dead_strip` in asm) Fixes PR49276. Differential Revision: https://reviews.llvm.org/D103324
2021-05-08 05:10:05 +08:00
# UNWIND-LABEL: SYMBOL TABLE:
# UNWIND-NEXT: l O __TEXT,__gcc_except_tab GCC_except_table1
# UNWIND-NEXT: l O __DATA,__data __dyld_private
# UNWIND-NEXT: g F __TEXT,__text _main
# UNWIND-NEXT: g F __TEXT,__text __mh_execute_header
# UNWIND-NEXT: *UND* ___cxa_allocate_exception
# UNWIND-NEXT: *UND* ___cxa_end_catch
# UNWIND-NEXT: *UND* __ZTIi
# UNWIND-NEXT: *UND* ___cxa_throw
# UNWIND-NEXT: *UND* ___gxx_personality_v0
# UNWIND-NEXT: *UND* ___cxa_begin_catch
# UNWIND-NEXT: *UND* dyld_stub_binder
## If a dead stripped function has a strong ref to a dylib symbol but
## a live function only a weak ref, the dylib is still not a WEAK_DYLIB.
## This matches ld64.
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/weak-ref.s -o %t/weak-ref.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/strong-dead-ref.s -o %t/strong-dead-ref.o
# RUN: %lld -lSystem -dead_strip %t/weak-ref.o %t/strong-dead-ref.o \
# RUN: %t/dylib.dylib -o %t/weak-ref
# RUN: llvm-otool -l %t/weak-ref | FileCheck -DDIR=%t --check-prefix=WEAK %s
# WEAK: cmd LC_LOAD_DYLIB
# WEAK-NEXT: cmdsize
# WEAK-NEXT: name /usr/lib/libSystem.dylib
# WEAK: cmd LC_LOAD_DYLIB
# WEAK-NEXT: cmdsize
# WEAK-NEXT: name [[DIR]]/dylib.dylib
## A strong symbol that would override a weak import does not emit the
## "this overrides a weak import" opcode if it is dead-stripped.
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/weak-dylib.s -o %t/weak-dylib.o
# RUN: %lld -dylib -dead_strip %t/weak-dylib.o -o %t/weak-dylib.dylib
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/dead-weak-override.s -o %t/dead-weak-override.o
# RUN: %lld -dead_strip %t/dead-weak-override.o %t/weak-dylib.dylib \
# RUN: -o %t/dead-weak-override
# RUN: llvm-objdump --macho --weak-bind --private-header \
# RUN: %t/dead-weak-override | FileCheck --check-prefix=DEADWEAK %s
# DEADWEAK-NOT: WEAK_DEFINES
# DEADWEAK: Weak bind table:
# DEADWEAK: segment section address type addend symbol
# DEADWEAK-NOT: strong _weak_in_dylib
## Stripped symbols should not be in the debug info stabs entries.
# RUN: llvm-mc -g -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/debug.s -o %t/debug.o
# RUN: %lld -lSystem -dead_strip %t/debug.o -o %t/debug
# RUN: dsymutil -s %t/debug | FileCheck --check-prefix=EXECSTABS %s
# EXECSTABS-NOT: N_FUN {{.*}} '_unref'
# EXECSTABS: N_FUN {{.*}} '_main'
# EXECSTABS-NOT: N_FUN {{.*}} '_unref'
#--- basics.s
.comm _ref_com, 1
.comm _unref_com, 1
.section __DATA,__unref_section
_unref_data:
.quad 4
l_unref_data:
.quad 5
## Referenced by no_dead_strip == S_ATTR_NO_DEAD_STRIP
.section __DATA,__ref_section,regular,no_dead_strip
## Referenced because in no_dead_strip section.
_ref_data:
.quad 4
## This is a local symbol so it's not in the symbol table, but
## it is still in the section data.
l_ref_data:
.quad 5
.text
# Exported symbols should not be stripped from dylibs
# or bundles, but they should be stripped from executables.
.globl _unref_extern
_unref_extern:
callq _ref_local
retq
# Unreferenced local symbols should be stripped.
_unref_local:
retq
# Same for unreferenced private externs.
.globl _unref_private_extern
.private_extern _unref_private_extern
_unref_private_extern:
# This shouldn't create an indirect symbol since it's
# a reference from a dead function.
movb _unref_com@GOTPCREL(%rip), %al
retq
# Referenced local symbols should not be stripped.
_ref_local:
callq _ref_private_extern
retq
# Same for referenced private externs.
# This one is referenced by a relocation.
.globl _ref_private_extern
.private_extern _ref_private_extern
_ref_private_extern:
retq
# This one is referenced by a -u flag.
.globl _ref_private_extern_u
.private_extern _ref_private_extern_u
_ref_private_extern_u:
retq
# Entry point should not be stripped for executables, even if hidden.
# For shared libraries this is stripped since it's just a regular hidden
# symbol there.
.globl _main
.private_extern _main
_main:
movb _ref_com@GOTPCREL(%rip), %al
callq _ref_local
retq
# Things marked no_dead_strip should not be stripped either.
# (clang emits this e.g. for `__attribute__((used))` globals.)
# Both for .globl symbols...
.globl _no_dead_strip_globl
.no_dead_strip _no_dead_strip_globl
_no_dead_strip_globl:
callq _ref_from_no_dead_strip_globl
retq
_ref_from_no_dead_strip_globl:
retq
# ...and for locals.
.no_dead_strip _no_dead_strip_local
_no_dead_strip_local:
callq _ref_from_no_dead_strip_local
retq
_ref_from_no_dead_strip_local:
retq
.subsections_via_symbols
#--- exported-symbol.s
.text
.globl _unref_symbol
_unref_symbol:
retq
.globl _my_exported_symbol
_my_exported_symbol:
retq
.globl _main
_main:
retq
.subsections_via_symbols
#--- abs.s
.globl _abs1, _abs2, _abs3
.no_dead_strip _abs1
_abs1 = 1
_abs2 = 2
_abs3 = 3
.section __DATA,__foo,regular,no_dead_strip
# Absolute symbols are not in a section, so the no_dead_strip
# on the section above has no effect.
.globl _abs4
_abs4 = 4
.text
.globl _main
_main:
# This is relaxed away, so there's no relocation here and
# _abs3 isn't in the exported symbol table.
mov _abs3, %rax
retq
.subsections_via_symbols
#--- mod-funcs.s
## Roughly based on `clang -O2 -S` output for `struct A { A(); ~A(); }; A a;`
## for mod_init_funcs. mod_term_funcs then similar to that.
.section __TEXT,__StaticInit,regular,pure_instructions
__unref:
retq
_ref_from_init:
retq
_ref_init:
callq _ref_from_init
retq
_ref_from_term:
retq
_ref_term:
callq _ref_from_term
retq
.globl _main
_main:
retq
.section __DATA,__mod_init_func,mod_init_funcs
.quad _ref_init
.section __DATA,__mod_term_func,mod_term_funcs
.quad _ref_term
.subsections_via_symbols
#--- dylib.s
.text
.globl _ref_dylib_fun
_ref_dylib_fun:
retq
.globl _unref_dylib_fun
_unref_dylib_fun:
retq
.subsections_via_symbols
#--- strip-dylib-ref.s
.text
_unref:
callq _ref_dylib_fun
callq _unref_dylib_fun
callq _ref_undef_fun
callq _unref_undef_fun
retq
.globl _main
_main:
callq _ref_dylib_fun
callq _ref_undef_fun
retq
.subsections_via_symbols
#--- live-support.s
## In practice, live_support is used for instruction profiling
## data and asan. (Also for __eh_frame, but that needs special handling
## in the linker anyways.)
## This test isn't based on anything happening in real code though.
.section __TEXT,__ref_ls_fw,regular,live_support
_ref_ls_fun_fw:
# This is called by _main and is kept alive by normal
# forward liveness propagation, The live_support attribute
# does nothing in this case.
retq
.section __TEXT,__unref_ls_fw,regular,live_support
_unref_ls_fun_fw:
retq
.section __TEXT,__ref_ls_bw,regular,live_support
_ref_ls_fun_bw:
# This _calls_ something that's alive but isn't referenced itself. This is
# kept alive only due to this being in a live_support section.
callq _foo
# _bar on the other hand is kept alive since it's called from here.
callq _bar
retq
## Kept alive by a live symbol form a dynamic library.
_ref_ls_dylib_fun:
callq _ref_dylib_fun
retq
## Kept alive by a live undefined symbol.
_ref_ls_undef_fun:
callq _ref_undef_fun
retq
## All symbols in this live_support section reference dead symbols
## and are hence dead themselves.
.section __TEXT,__unref_ls_bw,regular,live_support
_unref_ls_fun_bw:
callq _unref
retq
_unref_ls_dylib_fun_bw:
callq _unref_dylib_fun
retq
_unref_ls_undef_fun_bw:
callq _unref_undef_fun
retq
.text
.globl _unref
_unref:
retq
.globl _bar
_bar:
retq
.globl _foo
_foo:
callq _ref_ls_fun_fw
retq
.globl _main
_main:
callq _ref_ls_fun_fw
callq _foo
callq _ref_dylib_fun
callq _ref_undef_fun
retq
.subsections_via_symbols
#--- live-support-iterations.s
.section __TEXT,_ls,regular,live_support
## This is a live_support subsection that only becomes
## live after _foo below is processed. This means the algorithm of
## 1. mark things reachable from gc roots live
## 2. go through live sections and mark the ones live pointing to
## live symbols or sections
## needs more than one iteration, since _bar won't be live when step 2
## runs for the first time.
## (ld64 gets this wrong -- it has different output based on if _bar is
## before _foo or after it.)
_bar:
callq _foo_refd
callq _bar_refd
retq
## Same here. This is maybe more interesting since it references a live_support
## symbol instead of a "normal" symbol.
_baz:
callq _foo_refd
callq _baz_refd
retq
_foo:
callq _main
callq _foo_refd
retq
## Test no_dead_strip on a symbol in a live_support section.
## ld64 ignores this, but that doesn't look intentional. So lld honors it.
.no_dead_strip
_quux:
retq
.text
.globl _main
_main:
movq $0, %rax
retq
_foo_refd:
retq
_bar_refd:
retq
_baz_refd:
retq
.subsections_via_symbols
#--- unwind.s
## This is the output of `clang -O2 -S throw.cc` where throw.cc
## looks like this:
## void unref() {}
## int main() {
## try {
## throw 0;
## } catch (int i) {
## return i;
## }
## }
.section __TEXT,__text,regular,pure_instructions
.globl __Z5unrefv
.p2align 4, 0x90
__Z5unrefv:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset %rbp, -16
movq %rsp, %rbp
.cfi_def_cfa_register %rbp
popq %rbp
retq
.cfi_endproc
.globl _main
.p2align 4, 0x90
_main:
Lfunc_begin0:
.cfi_startproc
.cfi_personality 155, ___gxx_personality_v0
.cfi_lsda 16, Lexception0
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset %rbp, -16
movq %rsp, %rbp
.cfi_def_cfa_register %rbp
pushq %rbx
pushq %rax
.cfi_offset %rbx, -24
movl $4, %edi
callq ___cxa_allocate_exception
movl $0, (%rax)
Ltmp0:
movq __ZTIi@GOTPCREL(%rip), %rsi
movq %rax, %rdi
xorl %edx, %edx
callq ___cxa_throw
Ltmp1:
ud2
LBB1_2:
Ltmp2:
movq %rax, %rdi
callq ___cxa_begin_catch
movl (%rax), %ebx
callq ___cxa_end_catch
movl %ebx, %eax
addq $8, %rsp
popq %rbx
popq %rbp
retq
Lfunc_end0:
.cfi_endproc
.section __TEXT,__gcc_except_tab
.p2align 2
GCC_except_table1:
Lexception0:
.byte 255 ## @LPStart Encoding = omit
.byte 155 ## @TType Encoding = indirect pcrel sdata4
.uleb128 Lttbase0-Lttbaseref0
Lttbaseref0:
.byte 1 ## Call site Encoding = uleb128
.uleb128 Lcst_end0-Lcst_begin0
Lcst_begin0:
.uleb128 Lfunc_begin0-Lfunc_begin0 ## >> Call Site 1 <<
.uleb128 Ltmp0-Lfunc_begin0 ## Call between Lfunc_begin0 and Ltmp0
.byte 0 ## has no landing pad
.byte 0 ## On action: cleanup
.uleb128 Ltmp0-Lfunc_begin0 ## >> Call Site 2 <<
.uleb128 Ltmp1-Ltmp0 ## Call between Ltmp0 and Ltmp1
.uleb128 Ltmp2-Lfunc_begin0 ## jumps to Ltmp2
.byte 1 ## On action: 1
.uleb128 Ltmp1-Lfunc_begin0 ## >> Call Site 3 <<
.uleb128 Lfunc_end0-Ltmp1 ## Call between Ltmp1 and Lfunc_end0
.byte 0 ## has no landing pad
.byte 0 ## On action: cleanup
Lcst_end0:
.byte 1 ## >> Action Record 1 <<
## Catch TypeInfo 1
.byte 0 ## No further actions
.p2align 2
## >> Catch TypeInfos <<
.long __ZTIi@GOTPCREL+4 ## TypeInfo 1
Lttbase0:
.p2align 2
## -- End function
.subsections_via_symbols
#--- weak-ref.s
.text
.weak_reference _ref_dylib_fun
.globl _main
_main:
callq _ref_dylib_fun
retq
.subsections_via_symbols
#--- strong-dead-ref.s
.text
.globl _unref_dylib_fun
_unref:
callq _unref_dylib_fun
retq
.subsections_via_symbols
#--- weak-dylib.s
.text
.globl _weak_in_dylib
.weak_definition _weak_in_dylib
_weak_in_dylib:
retq
.subsections_via_symbols
#--- dead-weak-override.s
## Overrides the _weak_in_dylib symbol in weak-dylib, but is dead stripped.
.text
#.no_dead_strip _weak_in_dylib
.globl _weak_in_dylib
_weak_in_dylib:
retq
.globl _main
_main:
retq
.subsections_via_symbols
#--- debug.s
.text
.globl _unref
_unref:
retq
.globl _main
_main:
retq
.subsections_via_symbols