Re: [PATCH] gcov: No atomic ops for -fprofile-update=single

[Sebastian Huber <sebastian.huber@embedded-brains.de>]

On 23.11.23 15:19, Richard Biener wrote:
> On Thu, Nov 23, 2023 at 2:47 PM Sebastian Huber
> <sebastian.huber@embedded-brains.de>  wrote:
>> gcc/ChangeLog:
>>          PR tree-optimization/112678
>>
>>          * tree-profile.cc (tree_profiling): Do not use atomic operations
>>          for -fprofile-update=single.
>> ---
>>   gcc/tree-profile.cc | 8 +++++---
>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/gcc/tree-profile.cc b/gcc/tree-profile.cc
>> index 1ac0fdb3bc98..9c8fdb8b18f4 100644
>> --- a/gcc/tree-profile.cc
>> +++ b/gcc/tree-profile.cc
>> @@ -767,6 +767,7 @@ tree_profiling (void)
>>       = HAVE_sync_compare_and_swapsi || HAVE_atomic_compare_and_swapsi;
>>     bool have_atomic_8
>>       = HAVE_sync_compare_and_swapdi || HAVE_atomic_compare_and_swapdi;
>> +  bool needs_split = gcov_type_size == 8 && !have_atomic_8 && have_atomic_4;
>>     if (!can_support_atomic)
>>       {
>>         if (gcov_type_size == 4)
>> @@ -775,6 +776,9 @@ tree_profiling (void)
>>          can_support_atomic = have_atomic_8;
>>       }
>>
>> +  if (flag_profile_update != PROFILE_UPDATE_SINGLE && needs_split)
>> +    counter_update = COUNTER_UPDATE_ATOMIC_PARTIAL;
>> +
> I wonder if it's cleaner to set can_support_atomic when we can support
> it with splitting instead, avoiding a != PROFILE_UPDATE_SINGLE check
> here?

The bug was that counter_update was set to COUNTER_UPDATE_ATOMIC_PARTIAL 
for -fprofile-update=single. I don't think we can get rid of the 
flag_profile_update != PROFILE_UPDATE_SINGLE without changing this whole 
code block considerably.

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