Re: [AArch64] Fall back to -fPIC if no support of -fpic relocation modifer in assembler

[James Greenhalgh <james.greenhalgh@arm.com>]

On Mon, Jun 29, 2015 at 01:42:13PM +0100, Jiong Wang wrote:
> 
> This patch fix the breakage caused by
> 
>   https://gcc.gnu.org/ml/gcc-patches/2015-06/msg01913.html
> 
> We fall back to -fPIC if there is no assembler support on those new
> relocation modifiers for -fpic.
> 
> OK for trunk?
> 
> gcc/
>   * configure.ac: Add check for aarch64 assembler -fpic relocation
>   modifier support.
>   * configure: Regenerate.
>   * config.in: Regenerate.
>   * config/aarch64/aarch64.c (initialize_aarch64_code_model): Fall back to
>   -fPIC if not support of -fpic relocation modifier in assembler.
> -- 
> Regards,
> Jiong

This patch is OK, but please rename

> +#undef HAVE_AS_SPIC_RELOCS

to

  HAVE_AS_SMALL_PIC_RELOCS

It seems clearer to explicitly spell out what feature this relates to.

Thanks,
James

> 

> diff --git a/gcc/config.in b/gcc/config.in
> index 3aee936..476d585 100644
> --- a/gcc/config.in
> +++ b/gcc/config.in
> @@ -606,6 +606,12 @@
>  #endif
>  
>  
> +/* Define if your assembler supports relocs needed by -fpic. */
> +#ifndef USED_FOR_TARGET
> +#undef HAVE_AS_SPIC_RELOCS
> +#endif
> +
> +
>  /* Define if your assembler and linker support thread-local storage. */
>  #ifndef USED_FOR_TARGET
>  #undef HAVE_AS_TLS
> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> index f130f8d..7e09e3b 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -7581,9 +7581,13 @@ initialize_aarch64_code_model (void)
>  	   aarch64_cmodel = AARCH64_CMODEL_TINY_PIC;
>  	   break;
>  	 case AARCH64_CMODEL_SMALL:
> +#ifdef HAVE_AS_SPIC_RELOCS
>  	   aarch64_cmodel = (flag_pic == 2
>  			     ? AARCH64_CMODEL_SMALL_PIC
>  			     : AARCH64_CMODEL_SMALL_SPIC);
> +#else
> +	   aarch64_cmodel = AARCH64_CMODEL_SMALL_PIC;
> +#endif
>  	   break;
>  	 case AARCH64_CMODEL_LARGE:
>  	   sorry ("code model %qs with -f%s", "large",
> diff --git a/gcc/configure b/gcc/configure
> index 3f3f578..b72cde7 100755
> --- a/gcc/configure
> +++ b/gcc/configure
> @@ -24228,6 +24228,40 @@ $as_echo "#define HAVE_AS_MABI_OPTION 1" >>confdefs.h
>          done
>        fi
>      fi
> +    # Check if we have binutils support for relocations types needed by -fpic
> +    { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for -fpic relocs" >&5
> +$as_echo_n "checking assembler for -fpic relocs... " >&6; }
> +if test "${gcc_cv_as_aarch64_picreloc+set}" = set; then :
> +  $as_echo_n "(cached) " >&6
> +else
> +  gcc_cv_as_aarch64_picreloc=no
> +  if test x$gcc_cv_as != x; then
> +    $as_echo '
> +	.text
> +	ldr     x0, [x2, #:gotpage_lo15:globalsym]
> +    ' > conftest.s
> +    if { ac_try='$gcc_cv_as $gcc_cv_as_flags  -o conftest.o conftest.s >&5'
> +  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> +  (eval $ac_try) 2>&5
> +  ac_status=$?
> +  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> +  test $ac_status = 0; }; }
> +    then
> +	gcc_cv_as_aarch64_picreloc=yes
> +    else
> +      echo "configure: failed program was" >&5
> +      cat conftest.s >&5
> +    fi
> +    rm -f conftest.o conftest.s
> +  fi
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_as_aarch64_picreloc" >&5
> +$as_echo "$gcc_cv_as_aarch64_picreloc" >&6; }
> +if test $gcc_cv_as_aarch64_picreloc = yes; then
> +
> +$as_echo "#define HAVE_AS_SPIC_RELOCS 1" >>confdefs.h
> +
> +fi
>      # Enable default workaround for AArch64 Cortex-A53 erratum 835769.
>      # Check whether --enable-fix-cortex-a53-835769 was given.
>  if test "${enable_fix_cortex_a53_835769+set}" = set; then :
> diff --git a/gcc/configure.ac b/gcc/configure.ac
> index 85f72d5..fb7dbfb 100644
> --- a/gcc/configure.ac
> +++ b/gcc/configure.ac
> @@ -3562,6 +3562,13 @@ case "$target" in
>          done
>        fi
>      fi
> +    # Check if we have binutils support for relocations types needed by -fpic
> +    gcc_GAS_CHECK_FEATURE([-fpic relocs], gcc_cv_as_aarch64_picreloc,,,
> +    [
> +	.text
> +	ldr     x0, [[x2, #:gotpage_lo15:globalsym]]
> +    ],,[AC_DEFINE(HAVE_AS_SPIC_RELOCS, 1,
> +	[Define if your assembler supports relocs needed by -fpic.])])
>      # Enable default workaround for AArch64 Cortex-A53 erratum 835769.
>      AC_ARG_ENABLE(fix-cortex-a53-835769,
>      [