On 07/03/2018 11:55 AM, Segher Boessenkool wrote:
> On Tue, Jul 03, 2018 at 10:53:20AM +0200, Martin Liška wrote:
>> On 06/29/2018 09:04 PM, Jeff Law wrote:
>>> I think this is fine for the trunk.
>>>
>>> jeff
>>
>> Thank you Jeff.
>>
>> I found some issues when doing build of all targets (contrib/config-list.mk).
>> I'll update patch and test that affected cross-compilers still produce same
>> output.
>>
>> However I noticed one ppc64 issue:
>>
>> $ cat -n gcc/config/powerpcspe/powerpcspe.c
>>
>> 5401 /* Set branch target alignment, if not optimizing for size. */
>> 5402 if (!optimize_size)
>> 5403 {
>> 5404 /* Cell wants to be aligned 8byte for dual issue. Titan
>> wants to be
>> 5405 aligned 8byte to avoid misprediction by the branch
>> predictor. */
>> 5406 if (rs6000_cpu == PROCESSOR_TITAN
>> 5407 || rs6000_cpu == PROCESSOR_CELL)
>> 5408 {
>> 5409 if (align_functions <= 0)
>> 5410 align_functions = 8;
>> 5411 if (align_jumps <= 0)
>> 5412 align_jumps = 8;
>> 5413 if (align_loops <= 0)
>> 5414 align_loops = 8;
>> 5415 }
>> 5416 if (rs6000_align_branch_targets)
>> 5417 {
>> 5418 if (align_functions <= 0)
>> 5419 align_functions = 16;
>> 5420 if (align_jumps <= 0)
>> 5421 align_jumps = 16;
>> 5422 if (align_loops <= 0)
>> 5423 {
>> 5424 can_override_loop_align = 1;
>> 5425 align_loops = 16;
>> 5426 }
>> 5427 }
>> 5428 if (align_jumps_max_skip <= 0)
>> 5429 align_jumps_max_skip = 15;
>> 5430 if (align_loops_max_skip <= 0)
>> 5431 align_loops_max_skip = 15;
>>
>> Note that at line 5429 there's set of align_jumps_max_skip to 15 if not set
>> by default.
>> At line 5412 align_jumps is set to 8, and align_jumps_max_skip should be
>> equal align_jumps - 1.
>> That's a discrepancy. Segher can you please take a look?
>
> This is powerpcspe, that's not mine.
>
> But rs6000 has the same code, sure.
Right, that why I wrote to you.
> Why do you say "align_jumps_max_skip
> should be equal align_jumps - 1"? If that were true, why does it exist
> at all?
>
> toplev.c already has (in init_alignments):
>
> if (align_jumps_max_skip > align_jumps)
> align_jumps_max_skip = align_jumps - 1;
I'm rewriting this logic in the patch set. Issue is that
checking for value of align_jumps_max_skip is done
in rs6000_option_override_internal, which is place before
align_jumps_max_skip is parsed.
That said, 'align_jumps_max_skip <= 0' is always true.
Martin
>
> so why would targets duplicate that logic? (The target override is called
> before init_alignments).
>
>
> Segher
>
