Set insn_last_address in final_1

[Richard Biener]

On Mon, Apr 9, 2018 at 7:43 PM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> final_1 already sets insn_current_address for each instruction, making
> it possible to use some of the address functions in final.c during
> assembly generation.  This patch also sets insn_last_address, since
> as the comment says, we can treat final as a shorten_branches pass that
> does nothing.  It's then possible to use insn_current_reference_address
> during final as well.
>
> This is needed for the aarch64.md definitions of far_branch to work:
>
>    (set (attr "far_branch")
>         (if_then_else (and (ge (minus (match_dup 2) (pc)) (const_int -1048576))
>                            (lt (minus (match_dup 2) (pc)) (const_int 1048572)))
>                       (const_int 0)
>                       (const_int 1)))]
>
> This value (tested only during final) uses the difference between
> the INSN_ADDRESSES of operand 2 and insn_current_reference_address
> to calculate a conservatively-correct estimate of the branch distance.
> It takes into account the worst-case gap due to alignment, whereas
> a direct comparison of INSN_ADDRESSES would give an unreliable,
> optimistic result.
>
> Tested on aarch64-linux-gnu and x86_64-linux-gnu.  Sameera confirms
> that it fixes the original bug, but there's no sharable testcase.
> OK to install?

OK.

Richard.

> Richard
>
>
> 2018-04-09  Richard Sandiford  <richard.sandiford@linaro.org>
>
> gcc/
>         * final.c (final_1): Set insn_last_address as well as
>         insn_current_address.
>
> Index: gcc/final.c
> ===================================================================
> --- gcc/final.c 2018-04-09 18:40:26.887628387 +0100
> +++ gcc/final.c 2018-04-09 18:40:27.033624471 +0100
> @@ -2081,6 +2081,9 @@ final_1 (rtx_insn *first, FILE *file, in
>             }
>           else
>             insn_current_address = INSN_ADDRESSES (INSN_UID (insn));
> +         /* final can be seen as an iteration of shorten_branches that
> +            does nothing (since a fixed point has already been reached).  */
> +         insn_last_address = insn_current_address;
>         }
>
>        dump_basic_block_info (file, insn, start_to_bb, end_to_bb,