----- Am 27. Dez 2025 um 0:43 schrieb Jeff Law [email protected]:
> On 12/7/2025 5:11 AM, Sebastian Huber wrote:
[...]
>> +
>> + /* Get the high 32-bit of the counter */
>> + tree shift_32 = build_int_cst (integer_type_node, 32);
>> + tree counter_high_64 = make_temp_ssa_name (gcov_type_node, NULL,
>> + "PROF_decision");
>> + gassign *assign3 = gimple_build_assign (counter_high_64, LSHIFT_EXPR,
>> + counter, shift_32);
>
> Doesn't the type of shift_32 need to match the type of the object being
> shifted? Or do we have loose requirements around type checking operands
> for this case (where the shift count is often in a smaller precision
> than the object being shifted).
This is my attempt to write something like this:
int shift_32 = 32;
gcov_type_node counter_high_64 = counter >> shift_32;
>
> Do we need to worry about logical vs arithmetic shifts here? COUNTER's
> type is going to drive that decision, so we just need to make sure it's
> sensible.
We have
tree
get_gcov_type (void)
{
scalar_int_mode mode
= smallest_int_mode_for_size
(LONG_LONG_TYPE_SIZE > 32 ? 64 : 32).require ();
return lang_hooks.types.type_for_mode (mode, false);
}
So, the gcov_type_node is probably a signed type.
With
gassign *assign4 = gimple_build_assign (counter_high_32, NOP_EXPR,
counter_high_64);
does it matter if it is a logical or arithmetic shift? I am sorry, but I don't
really know what I am doing here. I tinkered this together by looking at
examples in the code.
>
>
>>
>>
>> @@ -1157,6 +1213,11 @@ instrument_decisions (array_slice<basic_block> expr,
>> size_t condno,
>> next[k], relaxed);
>> gsi_insert_on_edge (e, flush);
>> }
>> + else if (use_atomic_split)
>> + {
>> + split_update_decision_counter (e, ref, next[k],
>> + atomic_ior_32, relaxed);
>> + }
>
> Consider dropping the extraneous curlys. That function seems to be
> formatted without regard to our formatting conventions, so I'm not going
> to ask that you adjust indention on this little hunk since it mirrors
> nearby code.
Ok, I adjusted the patch.
--
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