Re: [PATCH 01/11] nds32: Build Infastructure

[Vincent Chen <vincentc at andestech dot com>]

On Tue, May 08, 2018 at 10:49:26PM +0800, Joseph Myers wrote:
> On Sun, 6 May 2018, vincentc wrote:
> 
> > diff --git a/sysdeps/nds32/configure.ac b/sysdeps/nds32/configure.ac
> > new file mode 100644
> > index 0000000..4ca57b8
> > --- /dev/null
> > +++ b/sysdeps/nds32/configure.ac
> > @@ -0,0 +1,14 @@
> > +GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
> > +# Local configure fragment for sysdeps/nds32.
> > +CFLAGS="$CFLAGS -minline-asm-r15"
> 
> If that option is needed globally for building glibc, a comment should be 
> there to explain it.
>
Ok, I will add the following comment in next version patch.

# For nds32 ABI, the $r15 register, assembler reserved register, is also used to
# storing the syscall number for issuing syscall. In order to ensure the data
# safety, $r15 is included in clobber list by default. Using the option
# -minline-asm-r15 can avoid the conflict between asm-specifier for syscall number
# and clobber list when using inline assembly to issue syscall.

 
> > +AC_CACHE_CHECK(whether gcc support option -mno-scalbn-transform,
> > +	       libc_cv_scalbn_transform, [dnl
> > +save_CFLAGS="$CFLAGS"
> > +CFLAGS="$CFLAGS -mno-scalbn-transform"
> 
> What does this option do (I don't see it in current GCC)?  Since you've 
> said current GCC versions aren't suitable for building glibc, can't you 
> just require a compiler supporting the option, unconditionally, so any 
> test for it is just to ensure a configure error for a too-old compiler 
> rather than allowing compilation to continue without support?
> 

The -mno-scalbn-transfomr is used to disable nds32 specific feature in gcc 6.3.0.
(We put nds32 gcc-6.3.0 in the git repo https://github.com/andestech/gcc.git)
However, this feature will be deprecated in the latest gcc. We plan to disable 
this feature by default in gcc-6.3.0 too. Therefore, I will remove this option
from the configure in the next version patch.

Thanks

Best regards
Vincent Chen


> -- 
> Joseph S. Myers
> joseph@codesourcery.com