Re: [PATCH] MIPS/GCC: Unconditional jump generation bug fix

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

"Maciej W. Rozycki" <macro@codesourcery.com> writes:
> 2014-11-17  Maciej W. Rozycki  <macro@codesourcery.com>
>
> 	gcc/
> 	* gcc/config/mips/mips.md (*jump_absolute): Use a branch when in
> 	range, a jump otherwise.
>
>   Maciej
>
> gcc-mips-jump-branch.diff
> Index: gcc-fsf-trunk-quilt/gcc/config/mips/mips.md
> ===================================================================
> --- gcc-fsf-trunk-quilt.orig/gcc/config/mips/mips.md	2014-11-16 19:54:17.000000000 +0000
> +++ gcc-fsf-trunk-quilt/gcc/config/mips/mips.md	2014-11-17 04:44:32.847732003 +0000
> @@ -5957,14 +5957,12 @@
>  	(label_ref (match_operand 0)))]
>    "!TARGET_MIPS16 && TARGET_ABSOLUTE_JUMPS"
>  {
> -  /* Use a branch for microMIPS.  The assembler will choose
> -     a 16-bit branch, a 32-bit branch, or a 32-bit jump.  */
> -  if (TARGET_MICROMIPS && !TARGET_ABICALLS_PIC2)
> +  if (get_attr_length (insn) <= 8)
>      return "%*b\t%l0%/";
>    else
>      return MIPS_ABSOLUTE_JUMP ("%*j\t%l0%/");
>  }
> -  [(set_attr "type" "jump")])
> +  [(set_attr "type" "branch")])

You didn't mention it explicitly, but this will have the effect of
overestimating the length of the insn by 8 bytes in cases where the
jump is used.  That might be an acceptable trade-off (even for
non-microMIPS code) but it's probably worth mentioning in a comment.

Thanks,
Richard