Re: [PATCH v3 2/9] Introduce rtx_alloca, alloca_raw_REG and alloca_rtx_fmt_*

[Richard Sandiford <richard.sandiford@arm.com>]

Ilya Leoshkevich <iii@linux.ibm.com> writes:
> One of the next patches in series needs to frequently pass short-lived
> fake rtxes to the back-end in order to test its capabilities.  In order
> to reduce the load on GC, it is beneficial to allocate these rtxes on
> stack.
>
> Provide the macro counterparts of gen_* functions required by the next
> patch in series.
>
> gcc/ChangeLog:
>
> 2019-08-27  Ilya Leoshkevich  <iii@linux.ibm.com>
>
> 	PR target/77918
> 	* emit-rtl.c (gen_raw_REG): Use init_raw_REG.
> 	(init_raw_REG): New function.
> 	* gengenrtl.c (gendef): Emit init_* functions and alloca_*
> 	macros.
> 	* rtl.c (rtx_alloc_stat_v): Use rtx_init.
> 	* rtl.h (rtx_init): New function.
> 	(rtx_alloca): New function.
> 	(init_raw_REG): New function.
> 	(alloca_raw_REG): New macro.
> ---
>  gcc/emit-rtl.c  | 15 +++++++++---
>  gcc/gengenrtl.c | 64 +++++++++++++++++++++++++++++++++++++------------
>  gcc/rtl.c       |  7 +-----
>  gcc/rtl.h       | 12 ++++++++++
>  4 files changed, 74 insertions(+), 24 deletions(-)
>
> diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
> index a667cdab94e..ecfa3735bba 100644
> --- a/gcc/emit-rtl.c
> +++ b/gcc/emit-rtl.c
> @@ -466,20 +466,29 @@ set_mode_and_regno (rtx x, machine_mode mode, unsigned int regno)
>    set_regno_raw (x, regno, nregs);
>  }
>  
> -/* Generate a new REG rtx.  Make sure ORIGINAL_REGNO is set properly, and
> +/* Initialize a REG rtx.  Make sure ORIGINAL_REGNO is set properly, and
>     don't attempt to share with the various global pieces of rtl (such as
>     frame_pointer_rtx).  */
>  
>  rtx
> -gen_raw_REG (machine_mode mode, unsigned int regno)
> +init_raw_REG (rtx x, machine_mode mode, unsigned int regno)
>  {
> -  rtx x = rtx_alloc (REG MEM_STAT_INFO);
>    set_mode_and_regno (x, mode, regno);
>    REG_ATTRS (x) = NULL;
>    ORIGINAL_REGNO (x) = regno;
>    return x;
>  }
>  
> +/* Generate a new REG rtx.  */
> +
> +rtx
> +gen_raw_REG (machine_mode mode, unsigned int regno)
> +{
> +  rtx x = rtx_alloc (REG MEM_STAT_INFO);
> +  init_raw_REG (x, mode, regno);
> +  return x;
> +}
> +

I think we should keep the gen_raw_REG comment the same (including
the "Make sure..." bit).  The point is to contrast gen_raw_REG with
gen_rtx_REG, which does various bits of sharing.

Maybe the comment above init_raw_REG can instead be just:

/* Initialize a fresh REG rtx with mode MODE and register REGNO.  */

> [...]
> @@ -266,16 +261,55 @@ gendef (const char *format)
>      else
>        printf ("  %s (rt, %d) = arg%d;\n", accessor_from_format (*p), i, j++);
>  
> -  puts ("\n  return rt;\n}\n");
> +  puts ("  return rt;\n}\n");
> +
> +  /* Write the definition of the gen function name and the types
> +     of the arguments.  */
> +
> +  puts ("static inline rtx");
> +  printf ("gen_rtx_fmt_%s_stat (RTX_CODE code, machine_mode mode", format);
> +  for (p = format, i = 0; *p != 0; p++)
> +    if (*p != '0')
> +      printf (",\n\t%sarg%d", type_from_format (*p), i++);
> +  puts (" MEM_STAT_DECL)");
> +
> +  /* Now write out the body of the function itself, which allocates
> +     the memory and initializes it.  */
> +  puts ("{");
> +  puts ("  rtx rt;\n");
> +
> +  puts ("  rt = rtx_alloc (code PASS_MEM_STAT);");
> +  printf ("  init_rtx_fmt_%s (rt, mode", format);
> +  for (p = format, i = 0; *p != 0; p++)
> +    if (*p != '0')
> +      printf (", arg%d", i++);
> +  puts (");\n");
> +
> +  puts ("  return rt;\n}\n");

Might as well make it:

  printf ("  return init_rtx_fmt_%s (rt, mode", format);

and drop the separate return, for consistency with the new
alloca code.

OK with those changes, thanks.

Richard