Re: [PATCH] Ensure that MIPS target code is compiled for the O32 ABI.

[Andrei Borzenkov <arvidjaar@gmail.com>]

22.08.2015 21:04, Mark H Weaver пишет:
> Andrei Borzenkov <arvidjaar@gmail.com> writes:
>
>> 19.08.2015 21:35, Mark H Weaver пишет:
>>> Include -mabi=32 in CFLAGS_PLATFORM and CCASFLAGS_PLATFORM to compile
>>> code for the O32 ABI when targetting MIPS, since the MIPS assembly code
>>> in GRUB assumes this.  This flag is also needed when compiling
>>> asm-tests/mips.S from configure, because GNU as rejects MIPS register
>>> names such as $t2 unless the O32 ABI is selected.

BTW, I assume this did work at some point; so this needs more verbose 
explanation what changed and why it stopped working.

>>> ---
>>>    conf/Makefile.common | 4 ++++
>>>    configure.ac         | 7 +++++--
>>>    2 files changed, 9 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/conf/Makefile.common b/conf/Makefile.common
>>> index fcb8d2e..bd125da 100644
>>> --- a/conf/Makefile.common
>>> +++ b/conf/Makefile.common
>>> @@ -20,6 +20,10 @@ endif
>>>    if COND_powerpc_ieee1275
>>>      CFLAGS_PLATFORM += -mcpu=powerpc
>>>    endif
>>> +if COND_mips
>>> +  CFLAGS_PLATFORM += -mabi=32
>>> +  CCASFLAGS_PLATFORM = -mabi=32
>>> +endif
>>>
>>
>> Does it work with clang?
>
> Based on the error message below, clang seems to accept and understand
> the -mabi=32 option, but the version of clang that we have in GNU Guix
> (which uses the N32 ABI on MIPS) seems to lack support for compiling for
> O32:
>
>    mhw@librenote:~$ clang -mabi=32 mips.S
>    error: unknown target CPU 'mips32r2'
>

Are you on native MIPS platform or cross-compiling? Which clang version? 
This works for me using current upstream clang (I do not have cross 
binutils so linking fails, but that's different story).

bor@bor-Latitude-E5450:~/build/grub$ ~/build/llvm/bin/clang 
--target=mips -mabi=32 -v -integrated-as -c asm-tests/mips.S
clang version 3.8.0 (git://github.com/llvm-mirror/clang.git 
2b06a033d151865ca944dedf899e9b36aa630f42) 
(git://github.com/llvm-mirror/llvm.git 
8f7e8462cdf3b0eed913202b81f14e2fead62be4)
Target: mips
Thread model: posix
InstalledDir: /home/bor/build/llvm/bin
  "/home/bor/build/llvm/bin/clang-3.8" -cc1 -triple mips -E 
-disable-free -main-file-name mips.S -mrelocation-model static 
-mthread-model posix -mdisable-fp-elim -fmath-errno 
-mconstructor-aliases -target-cpu mips32r2 -target-abi o32 -mfloat-abi 
hard -v -dwarf-column-info -coverage-file /home/bor/build/grub/mips.S 
-resource-dir /home/bor/build/llvm/bin/../lib/clang/3.8.0 
-fdebug-compilation-dir /home/bor/build/grub -ferror-limit 19 
-fmessage-length 95 -mstackrealign -fobjc-runtime=gcc 
-fdiagnostics-show-option -o /tmp/mips-b9949a.s -x assembler-with-cpp 
asm-tests/mips.S
clang -cc1 version 3.8.0 based upon LLVM 3.8.0svn default target 
x86_64-unknown-linux-gnu
#include "..." search starts here:
#include <...> search starts here:
  /usr/local/include
  /home/bor/build/llvm/bin/../lib/clang/3.8.0/include
  /usr/include
End of search list.
  "/home/bor/build/llvm/bin/clang-3.8" -cc1as -triple mips -filetype obj 
-main-file-name mips.S -target-cpu mips32r2 -fdebug-compilation-dir 
/home/bor/build/grub -dwarf-debug-producer clang version 3.8.0 
(git://github.com/llvm-mirror/clang.git 
2b06a033d151865ca944dedf899e9b36aa630f42) 
(git://github.com/llvm-mirror/llvm.git 
8f7e8462cdf3b0eed913202b81f14e2fead62be4) -mrelocation-model static 
-target-abi o32 -o mips.o /tmp/mips-b9949a.s

Actually this works for me also without -mabi=32 and produced object 
type is identical

> However, it doesn't work without that option either:
>
>    mhw@librenote:~$ clang mips.S
>    mips.S: Assembler messages:
>    mips.S:7: Error: invalid operands `ld $t2,0($t6)'
>    mips.S:10: Error: invalid operands `addiu $t7,$s0,(b-a)'
>    clang-3.6: error: assembler command failed with exit code 1 (use -v to see invocation)
>
> This is the same failure that occurs with gcc when configured to use the
> N32 ABI by default.  I also tried passing -fno-integrated-as in both
> cases above, but it made no difference.
>
>        Mark
>