Re: [PATCH 7/7] x86: introduce a state stack for .arch

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

On Thu, Jun 30, 2022 at 5:55 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> When using just slightly non-trivial combinations of .arch, it can be
> quite useful to be able to go back to prior state without needing to
> re-invoke perhaps many earlier directives and without needing to invoke
> perhaps many "negative" ones. Like some other architectures allow
> saving (pushing) and restoring (popping) present/prior state.
>
> For now require the same .code<N> to be in effect for ".arch pop" that
> was in effect for the corresponding ".arch push".
>
> Also change the global "no_cond_jump_promotion" to be bool, to match the
> new struct field.
>
> --- a/gas/config/tc-i386.c
> +++ b/gas/config/tc-i386.c
> @@ -788,7 +788,7 @@ i386_cpu_flags cpu_arch_isa_flags;
>
>  /* If set, conditional jumps are not automatically promoted to handle
>     larger than a byte offset.  */
> -static unsigned int no_cond_jump_promotion = 0;
> +static bool no_cond_jump_promotion = false;
>
>  /* Encode SSE instructions with VEX prefix.  */
>  static unsigned int sse2avx;
> @@ -2663,6 +2663,20 @@ extend_cpu_sub_arch_name (const char *na
>  static void
>  set_cpu_arch (int dummy ATTRIBUTE_UNUSED)
>  {
> +  typedef struct arch_stack_entry
> +  {
> +    const struct arch_stack_entry *prev;
> +    const char *name;
> +    char *sub_name;
> +    i386_cpu_flags flags;
> +    i386_cpu_flags isa_flags;
> +    enum processor_type isa;
> +    enum flag_code flag_code;
> +    char stackop_size;
> +    bool no_cond_jump_promotion;
> +  } arch_stack_entry;
> +  static const arch_stack_entry *arch_stack_top;
> +
>    SKIP_WHITESPACE ();
>
>    if (!is_end_of_line[(unsigned char) *input_line_pointer])
> @@ -2706,6 +2720,67 @@ set_cpu_arch (int dummy ATTRIBUTE_UNUSED
>               j = ARRAY_SIZE (cpu_arch) + 1;
>             }
>         }
> +      else if (strcmp (string, "push") == 0)
> +       {
> +         arch_stack_entry *top = XNEW (arch_stack_entry);
> +
> +         top->name = cpu_arch_name;
> +         if (cpu_sub_arch_name)
> +           top->sub_name = xstrdup (cpu_sub_arch_name);
> +         else
> +           top->sub_name = NULL;
> +         top->flags = cpu_arch_flags;
> +         top->isa = cpu_arch_isa;
> +         top->isa_flags = cpu_arch_isa_flags;
> +         top->flag_code = flag_code;
> +         top->stackop_size = stackop_size;
> +         top->no_cond_jump_promotion = no_cond_jump_promotion;
> +
> +         top->prev = arch_stack_top;
> +         arch_stack_top = top;
> +
> +         (void) restore_line_pointer (e);
> +         demand_empty_rest_of_line ();
> +         return;
> +       }
> +      else if (strcmp (string, "pop") == 0)
> +       {
> +         const arch_stack_entry *top = arch_stack_top;
> +
> +         if (!top)
> +           as_bad (_(".arch stack is empty"));
> +         else if (top->flag_code != flag_code
> +                  || top->stackop_size != stackop_size)
> +           {
> +             static const unsigned int bits[] = {
> +               [CODE_16BIT] = 16,
> +               [CODE_32BIT] = 32,
> +               [CODE_64BIT] = 64,
> +             };
> +
> +             as_bad (_("this `.arch pop' requires `.code%u%s' to be in effect"),
> +                     bits[top->flag_code],
> +                     top->stackop_size == LONG_MNEM_SUFFIX ? "gcc" : "");
> +           }
> +         else
> +           {
> +             arch_stack_top = top->prev;
> +
> +             cpu_arch_name = top->name;
> +             xfree (cpu_sub_arch_name);

Can we just use free?

> +             cpu_sub_arch_name = top->sub_name;
> +             cpu_arch_flags = top->flags;
> +             cpu_arch_isa = top->isa;
> +             cpu_arch_isa_flags = top->isa_flags;
> +             no_cond_jump_promotion = top->no_cond_jump_promotion;
> +
> +             XDELETE (top);
> +           }
> +
> +         (void) restore_line_pointer (e);
> +         demand_empty_rest_of_line ();
> +         return;
> +       }
>
>        for (; j < ARRAY_SIZE (cpu_arch); j++)
>         {
> @@ -13685,6 +13760,10 @@ show_arch (FILE *stream, int ext, int ch
>      {
>        p = output_message (stream, p, message, start, &left,
>                           STRING_COMMA_LEN ("default"));
> +      p = output_message (stream, p, message, start, &left,
> +                         STRING_COMMA_LEN ("push"));
> +      p = output_message (stream, p, message, start, &left,
> +                         STRING_COMMA_LEN ("pop"));
>      }
>
>    for (j = 0; j < ARRAY_SIZE (cpu_arch); j++)
> --- a/gas/doc/c-i386.texi
> +++ b/gas/doc/c-i386.texi
> @@ -1504,7 +1504,7 @@ directive enables a warning when gas det
>  supported on the CPU specified.  The choices for @var{cpu_type} are:
>
>  @multitable @columnfractions .20 .20 .20 .20
> -@item @samp{default}
> +@item @samp{default} @tab @samp{push} @tab @samp{pop}
>  @item @samp{i8086} @tab @samp{i186} @tab @samp{i286} @tab @samp{i386}
>  @item @samp{i486} @tab @samp{i586} @tab @samp{i686} @tab @samp{pentium}
>  @item @samp{pentiumpro} @tab @samp{pentiumii} @tab @samp{pentiumiii} @tab @samp{pentium4}
> --- /dev/null
> +++ b/gas/testsuite/gas/i386/arch-stk.l
> @@ -0,0 +1,43 @@
> +.*: Assembler messages:
> +.*:3: Error:.*`cmovl'.*
> +.*:10: Error:.*`cmovg'.*
> +.*:17: Error:.*`cmovz'.*
> +.*:21: Error:.*`\.arch pop'.*`\.code32'.*
> +.*:28: Error:.*`\.arch pop'.*`\.code16gcc'.*
> +.*:32: Error:.*\.arch.*empty.*
> +GAS LISTING .*
> +
> +
> +[      ]*[0-9]*[       ]+\.text
> +[      ]*[0-9]*[       ]+start:
> +[      ]*[0-9]*[       ]+cmovl %eax, %ecx
> +[      ]*[0-9]*[       ]*
> +[      ]*[0-9]*[       ]+\.arch push
> +[      ]*[0-9]*[       ]+\.arch default
> +[      ]*[0-9]*[       ]+\?\?\?\? 0F4DC8[      ]+cmovnl        %eax, %ecx
> +[      ]*[0-9]*[       ]*
> +[      ]*[0-9]*[       ]+\.arch pop
> +[      ]*[0-9]*[       ]+cmovg %eax, %ecx
> +[      ]*[0-9]*[       ]*
> +[      ]*[0-9]*[       ]+\.arch push
> +[      ]*[0-9]*[       ]+\.arch \.cmov
> +[      ]*[0-9]*[       ]+\?\?\?\? 0F4EC8[      ]+cmovng        %eax, %ecx
> +[      ]*[0-9]*[       ]*
> +[      ]*[0-9]*[       ]+\.arch pop
> +[      ]*[0-9]*[       ]+cmovz %eax, %ecx
> +[      ]*[0-9]*[       ]*
> +[      ]*[0-9]*[       ]+\.arch push
> +[      ]*[0-9]*[       ]+\.code16
> +[      ]*[0-9]*[       ]+\.arch pop
> +[      ]*[0-9]*[       ]+\.code32
> +[      ]*[0-9]*[       ]+\.arch pop
> +[      ]*[0-9]*[       ]*
> +[      ]*[0-9]*[       ]+\.code16gcc
> +[      ]*[0-9]*[       ]+\.arch push
> +[      ]*[0-9]*[       ]+\.code32
> +[      ]*[0-9]*[       ]+\.arch pop
> +[      ]*[0-9]*[       ]+\.code16gcc
> +[      ]*[0-9]*[       ]+\.arch pop
> +[      ]*[0-9]*[       ]*
> +[      ]*[0-9]*[       ]+\.arch pop
> +#pass
> --- /dev/null
> +++ b/gas/testsuite/gas/i386/arch-stk.s
> @@ -0,0 +1,34 @@
> +       .text
> +start:
> +       cmovl   %eax, %ecx
> +
> +       .arch push
> +       .arch default
> +       cmovnl  %eax, %ecx
> +
> +       .arch pop
> +       cmovg   %eax, %ecx
> +
> +       .arch push
> +       .arch .cmov
> +       cmovng  %eax, %ecx
> +
> +       .arch pop
> +       cmovz   %eax, %ecx
> +
> +       .arch push
> +       .code16
> +       .arch pop
> +       .code32
> +       .arch pop
> +
> +       .code16gcc
> +       .arch push
> +       .code32
> +       .arch pop
> +       .code16gcc
> +       .arch pop
> +
> +       .arch pop
> +
> +       .end
> --- a/gas/testsuite/gas/i386/i386.exp
> +++ b/gas/testsuite/gas/i386/i386.exp
> @@ -206,6 +206,7 @@ if [gas_32_check] then {
>      run_dump_test "arch-13"
>      run_dump_test "arch-14"
>      run_list_test "arch-dflt" "-march=generic32 -al"
> +    run_list_test "arch-stk" "-march=generic32 -al"
>      run_dump_test "8087"
>      run_dump_test "287"
>      run_dump_test "387"
>


-- 
H.J.