Keith
On 7 October 2013 05:20, Keith Packard keithp@keithp.com wrote:
Matthias Klose doko@ubuntu.com writes:
attaching a diff, comparing the two branches at a merge point (r201326), 398 lines.
Ok, thanks very much for this simple patch. First the good news -- I applied this patch to the 4.8.1 GCC sources included in debian and successfully built a cortex-m0 executable.
The bad news is that the gcc multilib support for arm appears to be broken, at least in this case.
- When I pass -mthumb -mcpu=cortex-m0 to gcc in the linking phase, the multilib configuration does not point at the thumb directory, and so the linker happily pulls libgcc.a from the arm directory. It looks like the multilib configuration that is generated is just wrong:
static const char *const multilib_raw[] = { ". !mthumb !marm !march=armv6s-m !march=armv7-m !march=armv7e-m !march=armv7 !mfloat-abi=softfp !mfloat-abi=hard !mfpu=fpv4-sp-d16 !mfpu=vfpv3-d16;", "thumb mthumb !marm !march=armv6s-m !march=armv7-m !march=armv7e-m !march=armv7 !mfloat-abi=softfp !mfloat-abi=hard !mfpu=fpv4-sp-d16 !mfpu=vfpv3-d16;", "arm !mthumb marm !march=armv6s-m !march=armv7-m !march=armv7e-m !march=armv7 !mfloat-abi=softfp !mfloat-abi=hard !mfpu=fpv4-sp-d16 !mfpu=vfpv3-d16;", "fpu !mthumb !marm !march=armv6s-m !march=armv7-m !march=armv7e-m !march=armv7 !mfloat-abi=softfp mfloat-abi=hard !mfpu=fpv4-sp-d16 !mfpu=vfpv3-d16;", NULL };
Can you please provide the output of: 1. arm-none-eabi-gcc -v 2. arm-none-eabi-gcc -print-multi-lib
My guess is that you've configured GCC using --with-mode=thumb, and other --with-* options. This is usually the wrong thing to do with multilibs.
The other thing to note is you need to specify what multilib architectures you want with --with-multilib-list when you configure: --with-multilib-list=armv6-m,armv7-m,armv7e-m,armv7-a,armv7-r Seems like a good initial try to me.
The 'thumb' directory is only selected if the -mthumb option is passed to the compiler *and* none of the thumb architecture flags (-march=armv6s-m for instance) are also passed.
So my reading of the multilib Makefile fragment is that the "thumb" directory is what you get when you specify -mthumb with no CPU or architecture option, and if you say -mcpu=cortex-m0 -mthumb you will get the armv6-m multilib directory.
- The thumb version of libgcc.a is not built with thumb instructions because GCC doesn't pass -mthumb to the assembler when it receives -mthumb on the command line.
I would be expecting the compiler to pass .thumb in the assembler source to as.
- That's ok, because the GNU assembler doesn't listen to -mthumb anyways; I had to force the assembler to compile thumb instructions by passing it -mcpu=cortex-m0 on the command line to GCC, which is then passed along to the assembler.
Figured you'd like to know what progress I've made, at this point it looks like simple driver bugs. Once resolved, it looks like I'll be able to generate a debian package from the debian GCC sources and a small patch.
I hope this helps.
Thanks,
Matt