Re: PATCH: Add .lcomm directive with optional alignment field to x86 port

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Wed, Sep 3, 2008 at 7:01 AM, Nick Clifton <nickc@redhat.com> wrote:
> Hi Guys,
>
>  I am checking in the patch below to add support for the .lcomm
>  directive with an optional alignment field to the i386 port of GAS.
>  This will allow a suitably modified gcc to generate properly aligned
>  static local values.  (I will be submitting a patch to the gcc
>  maintainers to make use of this new feature).
>
> Cheers
>  Nick
>
> gas/ChangeLog
> 2008-09-03  Nick Clifton  <nickc@redhat.com>
>
>        * config/tc-i386.c (pe_lcomm_internal): New function.  Allows the
>        alignment field of the .lcomm directive to be optional.
>        (pe_lcomm): New function.  Pass pe_lcomm_internal to
>        s_comm_internal.
>        (md_pseudo_table): Implement .lcomm directive for COFF based
>        targets.
>        * doc/c-i386.texi (i386-Directives): New node.  Used to document
>        the .lcomm directive.
>
> Index: gas/config/tc-i386.c
> ===================================================================
> RCS file: /cvs/src/src/gas/config/tc-i386.c,v
> retrieving revision 1.350
> diff -c -3 -p -r1.350 tc-i386.c
> *** gas/config/tc-i386.c        28 Aug 2008 09:42:11 -0000      1.350
> --- gas/config/tc-i386.c        3 Sep 2008 14:00:10 -0000
> *************** static const arch_entry cpu_arch[] =
> *** 684,689 ****
> --- 684,731 ----
>      CPU_SSE5_FLAGS },
>  };
>
> + /* Like s_lcomm_internal in gas/read.c but the alignment string
> +    is allowed to be optional.  */
> +
> + static symbolS *
> + pe_lcomm_internal (int needs_align, symbolS *symbolP, addressT size)
> + {
> +   addressT align = 0;
> +
> +   SKIP_WHITESPACE ();
> +
> +   if (needs_align
> +       && *input_line_pointer == ',')
> +     {
> +       align = parse_align (needs_align - 1);
> +
> +       if (align == (addressT) -1)
> +       return NULL;
> +     }
> +   else
> +     {
> +       if (size >= 8)
> +       align = 3;
> +       else if (size >= 4)
> +       align = 2;
> +       else if (size >= 2)
> +       align = 1;
> +       else
> +       align = 0;
> +     }
> +
> +   bss_alloc (symbolP, size, align);
> +   return symbolP;
> + }
> +
> + void pe_lcomm (int);

Can it be static? Can we define pe_lcomm and pe_lcomm_internal
for I386COFF only?

H.J.
---
> +
> + void
> + pe_lcomm (int needs_align)
> + {
> +   s_comm_internal (needs_align * 2, pe_lcomm_internal);
> + }
> +
>  const pseudo_typeS md_pseudo_table[] =
>  {
>  #if !defined(OBJ_AOUT) && !defined(USE_ALIGN_PTWO)
> *************** const pseudo_typeS md_pseudo_table[] =
> *** 694,699 ****
> --- 736,743 ----
>    {"arch", set_cpu_arch, 0},
>  #ifndef I386COFF
>    {"bss", s_bss, 0},
> + #else
> +   {"lcomm", pe_lcomm, 1},
>  #endif
>    {"ffloat", float_cons, 'f'},
>    {"dfloat", float_cons, 'd'},
> Index: gas/doc/c-i386.texi
> ===================================================================
> RCS file: /cvs/src/src/gas/doc/c-i386.texi,v
> retrieving revision 1.28
> diff -c -3 -p -r1.28 c-i386.texi
> *** gas/doc/c-i386.texi 2 May 2008 16:53:39 -0000       1.28
> --- gas/doc/c-i386.texi 3 Sep 2008 14:00:10 -0000
> *************** extending the Intel architecture to 64-b
> *** 23,28 ****
> --- 23,29 ----
>
>  @menu
>  * i386-Options::                Options
> + * i386-Directives::             X86 specific directives
>  * i386-Syntax::                 AT&T Syntax versus Intel Syntax
>  * i386-Mnemonics::              Instruction Naming
>  * i386-Regs::                   Register Naming
> *************** The @code{.att_syntax} and @code{.intel_
> *** 193,198 ****
> --- 194,224 ----
>
>  @end table
>
> + @node i386-Directives
> + @section x86 specific Directives
> +
> + @cindex machine directives, x86
> + @cindex x86 machine directives
> + @table @code
> +
> + @cindex @code{lcomm} directive, COFF
> + @item .lcomm @var{symbol} , @var{length}[, @var{alignment}]
> + Reserve @var{length} (an absolute expression) bytes for a local common
> + denoted by @var{symbol}.  The section and value of @var{symbol} are
> + those of the new local common.  The addresses are allocated in the bss
> + section, so that at run-time the bytes start off zeroed.  @var{Symbol}
> + is not declared global (@pxref{Global,,@code{.global}}), so is normally
> + not visible to @code{@value{LD}}.  The optional third parameter,
> + @var{alignment}, specifies the desired alignment of the symbol in the
> + bss section.
> +
> + This directive is only available for COFF based x86 targets.
> +
> + @c FIXME: Document other x86 specific directives ?  Eg: .code16gcc,
> + @c .largecomm
> +
> + @end table
> +
>  @node i386-Syntax
>  @section AT&T Syntax versus Intel Syntax
>
>



-- 
H.J.