On 06.09.19 12:48, Richard Biener wrote:
> On Fri, Sep 6, 2019 at 10:11 AM Andreas Krebbel <kreb...@linux.ibm.com> wrote:
>>
>> Hi,
>>
>> since this caused a critical performance regression in the OpenJ9 byte code
>> interpreter after
>> migrating from GCC 4.8 to GCC 7 I would like to backport this patch also to
>> GCC 8 and 9 branch.
>>
>> Ok - after bootstrap and regression test went fine?
>
> Looks reasonable to me. But what about GCC 7? I assume you also verified the
> actual performance regression is gone.
I've committed the patch to GCC 7 and 8 branch after verifying that the change
has the desired
effect on the source code file from OpenJ9.
GCC 9 branch is currently frozen. Ok, to apply there as well?
Andreas
>
> Richard.
>
>>
>> Andreas
>>
>>
>> commit d3dc20418aad41af83fe45ccba527deb0b334983
>> Author: krebbel <krebbel@138bc75d-0d04-0410-961f-82ee72b054a4>
>> Date: Thu Jun 6 11:35:04 2019 +0000
>>
>> Fix PR88751
>>
>> This patch implements a small improvement for the heuristic in lra
>> which decides when it has to activate the simpler register allocation
>> algorithm.
>>
>> gcc/ChangeLog:
>>
>> 2019-06-06 Andreas Krebbel <kreb...@linux.ibm.com>
>>
>> PR rtl-optimization/88751
>> * ira.c (ira): Use the number of the actually referenced
>> registers
>> when calculating the threshold.
>>
>>
>>
>> git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@271996
>> 138bc75d-0d04-0410-961f-82ee72b054a4
>>
>>
>> diff --git a/gcc/ira.c b/gcc/ira.c
>> index 4a14fb31583..725636d8dc5 100644
>> --- a/gcc/ira.c
>> +++ b/gcc/ira.c
>> @@ -5198,6 +5198,8 @@ ira (FILE *f)
>> int ira_max_point_before_emit;
>> bool saved_flag_caller_saves = flag_caller_saves;
>> enum ira_region saved_flag_ira_region = flag_ira_region;
>> + unsigned int i;
>> + int num_used_regs = 0;
>>
>> clear_bb_flags ();
>>
>> @@ -5213,12 +5215,17 @@ ira (FILE *f)
>>
>> ira_conflicts_p = optimize > 0;
>>
>> + /* Determine the number of pseudos actually requiring coloring. */
>> + for (i = FIRST_PSEUDO_REGISTER; i < DF_REG_SIZE (df); i++)
>> + num_used_regs += !!(DF_REG_USE_COUNT (i) + DF_REG_DEF_COUNT (i));
>> +
>> /* If there are too many pseudos and/or basic blocks (e.g. 10K
>> pseudos and 10K blocks or 100K pseudos and 1K blocks), we will
>> use simplified and faster algorithms in LRA. */
>> lra_simple_p
>> = (ira_use_lra_p
>> - && max_reg_num () >= (1 << 26) / last_basic_block_for_fn (cfun));
>> + && num_used_regs >= (1 << 26) / last_basic_block_for_fn (cfun));
>> +
>> if (lra_simple_p)
>> {
>> /* It permits to skip live range splitting in LRA. */
>>
