On 10/11/16 17:19, Wilco Dijkstra wrote:
> Improve the logic when setting max_insns_skipped. Limit the maximum size of
> IT
> to MAX_INSN_PER_IT_BLOCK as otherwise multiple IT instructions are needed,
> increasing codesize.
>
You don't provide any information about what benefits this brings.
> Given 4 works well for Thumb-2, use the same limit for ARM
> for consistency.
Why? Logic might suggest that given thumb has to execute an IT
instruction first, then allowing ARM to have one more conditional
instruction is the best answer.
R.
> ChangeLog:
> 2016-11-04 Wilco Dijkstra <wdijk...@arm.com>
>
> * config/arm/arm.c (arm_option_params_internal): Improve setting of
> max_insns_skipped.
> --
>
> diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> index
> f046854e9665d54911616fc1c60fee407188f7d6..29e8d1d07d918fbb2a627a653510dfc8587ee01a
> 100644
> --- a/gcc/config/arm/arm.c
> +++ b/gcc/config/arm/arm.c
> @@ -2901,20 +2901,12 @@ arm_option_params_internal (void)
> targetm.max_anchor_offset = TARGET_MAX_ANCHOR_OFFSET;
> }
>
> - if (optimize_size)
> - {
> - /* If optimizing for size, bump the number of instructions that we
> - are prepared to conditionally execute (even on a StrongARM). */
> - max_insns_skipped = 6;
> + /* Increase the number of conditional instructions with -Os. */
> + max_insns_skipped = optimize_size ? 4 : current_tune->max_insns_skipped;
>
> - /* For THUMB2, we limit the conditional sequence to one IT block. */
> - if (TARGET_THUMB2)
> - max_insns_skipped = arm_restrict_it ? 1 : 4;
> - }
> - else
> - /* When -mrestrict-it is in use tone down the if-conversion. */
> - max_insns_skipped = (TARGET_THUMB2 && arm_restrict_it)
> - ? 1 : current_tune->max_insns_skipped;
> + /* For THUMB2, we limit the conditional sequence to one IT block. */
> + if (TARGET_THUMB2)
> + max_insns_skipped = MIN (max_insns_skipped, MAX_INSN_PER_IT_BLOCK);
> }
>
> /* True if -mflip-thumb should next add an attribute for the default
>
