Re: Small change in NSObject.m ASM needed for PowerPC build

[Fred Kiefer]

David Chisnall wrote:
> I think it's important to work out why it is failing on your machine. 
> The reason I suggested this change is that, for me, looking at the
> assembly, it generates the same code as our inline asm on x86 but also
> works on non-x86 platforms that we currently use a painfully slow code
> path for.

I fully agree with you here.

> I am using GCC 4.2.1, and this compiles correctly with no -march=
> anything specified.  If I specify -march=i386 it still generates the
> LOCK.  Looking more deeply at the ISA references, it appears that the
> LOCK prefix was part of the original 80386 instruction set, so this is
> atomic on any x86 processor (it was the CMPXCHG instruction and friends
> that came in with the 80486).

That would be great, in this case, we did not loose any compatibility
with the last change and also wont with the new one.

> Possibly the GCC version check is incorrect.  According to the gcc docs,
> these functions appeared in 4.1.0, however it seems that 4.2 is when
> they became well-supported.  Possibly setting 4.2.0 or 4.2.1 as the
> minimum GCC version to adopt them will be better?

Again you are correct, better require a gcc version where we can be sure
it supports this correctly. Still this does not help on my machine, as I
wrote in the first mail I have gcc 4.3.2 installed. Here are the full specs:

 gcc -dumpspecs
*asm:
%{v:-V} %{Qy:} %{!Qn:-Qy} %{n} %{T} %{Ym,*} %{Yd,*} %{Wa,*:%*}

*asm_debug:
%{gstabs*:--gstabs}%{!gstabs*:%{g*:--gdwarf2}}
%{fdebug-prefix-map=*:--debug-prefix-map %*}

*asm_final:


*asm_options:
%{--target-help:%:print-asm-header()} %a %Y %{c:%W{o*}%{!o*:-o
%w%b%O}}%{!c:-o %d%w%u%O}

*invoke_as:
%{!S:-o %|.s |
 as %(asm_options) %|.s %A }

*cpp:
%{posix:-D_POSIX_SOURCE} %{pthread:-D_REENTRANT}

*cpp_options:
%(cpp_unique_options) %1 %{m*} %{std*&ansi&trigraphs} %{W*&pedantic*}
%{w} %{f*} %{g*:%{!g0:%{!fno-working-directory:-fworking-directory}}}
%{O*} %{undef} %{save-temps:-fpch-preprocess}

*cpp_debug_options:
%{d*}

*cpp_unique_options:
%{C|CC:%{!E:%eGCC does not support -C or -CC without -E}} %{!Q:-quiet}
%{nostdinc*} %{C} %{CC} %{v} %{I*&F*} %{P} %I %{MD:-MD
%{!o:%b.d}%{o*:%.d%*}} %{MMD:-MMD %{!o:%b.d}%{o*:%.d%*}} %{M} %{MM}
%{MF*} %{MG} %{MP} %{MQ*} %{MT*}
%{!E:%{!M:%{!MM:%{!MT:%{!MQ:%{MD|MMD:%{o*:-MQ %*}}}}}}} %{remap}
%{g3|ggdb3|gstabs3|gcoff3|gxcoff3|gvms3:-dD} %{H} %C %{D*&U*&A*} %{i*}
%Z %i %{fmudflap:-D_MUDFLAP -include mf-runtime.h}
%{fmudflapth:-D_MUDFLAP -D_MUDFLAPTH -include mf-runtime.h} %{E|M|MM:%W{o*}}

*trad_capable_cpp:
cc1 -E %{traditional|ftraditional|traditional-cpp:-traditional-cpp}

*cc1:
%(cc1_cpu) %{profile:-p}

*cc1_options:
%{pg:%{fomit-frame-pointer:%e-pg and -fomit-frame-pointer are
incompatible}} %1 %{!Q:-quiet} -dumpbase %B %{d*} %{m*} %{a*}
%{c|S:%{o*:-auxbase-strip %*}%{!o*:-auxbase %b}}%{!c:%{!S:-auxbase %b}}
%{g*} %{O*} %{W*&pedantic*} %{w} %{std*&ansi&trigraphs} %{v:-version}
%{pg:-p} %{p} %{f*} %{undef} %{Qn:-fno-ident} %{--help:--help}
%{--target-help:--target-help} %{--help=*:--help=%(VALUE)}
%{!fsyntax-only:%{S:%W{o*}%{!o*:-o %b.s}}} %{fsyntax-only:-o %j}
%{-param*} %{fmudflap|fmudflapth:-fno-builtin -fno-merge-constants}
%{coverage:-fprofile-arcs -ftest-coverage}

*cc1plus:


*link_gcc_c_sequence:
%{static:--start-group} %G %L %{static:--end-group}%{!static:%G}

*link_ssp:
%{fstack-protector:}

*endfile:
%{ffast-math|funsafe-math-optimizations:crtfastmath.o%s}
%{mpc32:crtprec32.o%s}    %{mpc64:crtprec64.o%s}
%{mpc80:crtprec80.o%s}    %{shared|pie:crtendS.o%s;:crtend.o%s} crtn.o%s

*link:
%{!r:--build-id} %{!static:--eh-frame-hdr} -m %(link_emulation)
%{shared:-shared}   %{!shared:     %{!ibcs:       %{!static:
%{rdynamic:-export-dynamic}     %{!dynamic-linker:-dynamic-linker
%(dynamic_linker)}}      %{static:-static}}}

*lib:
%{pthread:-lpthread}    %{shared:-lc}    %{!shared:%{mieee-fp:-lieee}
%{profile:-lc_p}%{!profile:-lc}}

*mfwrap:
 %{static: %{fmudflap|fmudflapth:  --wrap=malloc --wrap=free
--wrap=calloc --wrap=realloc --wrap=mmap --wrap=munmap --wrap=alloca}
%{fmudflapth: --wrap=pthread_create}} %{fmudflap|fmudflapth: --wrap=main}

*mflib:
%{fmudflap|fmudflapth: -export-dynamic}

*link_gomp:


*libgcc:
%{static|static-libgcc:-lgcc
-lgcc_eh}%{!static:%{!static-libgcc:%{!shared-libgcc:-lgcc --as-needed
-lgcc_s --no-as-needed}%{shared-libgcc:-lgcc_s%{!shared: -lgcc}}}}

*startfile:
%{!shared: %{pg|p|profile:gcrt1.o%s;pie:Scrt1.o%s;:crt1.o%s}}
crti.o%s %{static:crtbeginT.o%s;shared|pie:crtbeginS.o%s;:crtbegin.o%s}

*switches_need_spaces:


*cross_compile:
0

*version:
4.3.2

*multilib:
. ;

*multilib_defaults:


*multilib_extra:


*multilib_matches:


*multilib_exclusions:


*multilib_options:


*linker:
collect2

*link_libgcc:
%D

*md_exec_prefix:


*md_startfile_prefix:


*md_startfile_prefix_1:


*startfile_prefix_spec:


*sysroot_spec:
--sysroot=%R

*sysroot_suffix_spec:


*sysroot_hdrs_suffix_spec:


*cc1_cpu:
%{mcpu=*:-mtune=%* %n`-mcpu=' is deprecated. Use `-mtune=' or '-march='
instead.
} %<mcpu=* %{mintel-syntax:-masm=intel %n`-mintel-syntax' is deprecated.
Use `-masm=intel' instead.
} %{mno-intel-syntax:-masm=att %n`-mno-intel-syntax' is deprecated. Use
`-masm=att' instead.
}%{march=native:%<march=native %:local_cpu_detect(arch)
%{!mtune=*:%<mtune=native %:local_cpu_detect(tune)}}
%{mtune=native:%<mtune=native %:local_cpu_detect(tune)}

*link_emulation:
elf_i386

*dynamic_linker:
%{muclibc:%{mglibc:%e-mglibc and -muclibc used
together}/lib/ld-uClibc.so.0;:/lib/ld-linux.so.2}

*link_command:
%{!fsyntax-only:%{!c:%{!M:%{!MM:%{!E:%{!S:    %(linker) %l %{pie:-pie}
%X %{o*} %{A} %{d} %{e*} %{m} %{N} %{n} %{r}    %{s} %{t} %{u*} %{x}
%{z} %{Z} %{!A:%{!nostdlib:%{!nostartfiles:%S}}}    %{static:} %{L*}
%(mfwrap) %(link_libgcc) %o
%{fopenmp|ftree-parallelize-loops=*:%:include(libgomp.spec)%(link_gomp)}
%(mflib)    %{fprofile-arcs|fprofile-generate|coverage:-lgcov}
%{!nostdlib:%{!nodefaultlibs:%(link_ssp) %(link_gcc_c_sequence)}}
%{!A:%{!nostdlib:%{!nostartfiles:%E}}} %{T*} }}}}}}