This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH][middle-end] Make qsort in tree-ssa-sccvn.c stable.
2009/5/12 Richard Guenther <richard.guenther@gmail.com>:
> Splitting this into two functions is confusing. ?Also in general
> it doesn't make sense to distinguish things further.
The original comparison function returns 0 in the middle. If I want
to add check just for the cases where the original function returns 0,
the code becomes not simple to understand without use of gotoes.
Distinguishing things further makes sense because it make gcc computes
identical results, including generated code and debugging dumps, on
different hosts.
> I guess you are hitting the PHI node case, in which case I
> would suggest to simply do
>
> ? ? ?if (gimple_code (opstmta) == GIMPLE_PHI
> ? ? ? ? ?&& gimple_code (opstmtb) == GIMPLE_PHI)
> ? ? ? ?return SSA_NAME_VERSION (PHI_RESULT (opstmta)) -
> SSA_NAME_VERSION (PHI_RESULT (opstmtb));
>
> instead of return 0.
Will try this and an assert to see if that fixes my problem.
> Richard.
>
>
>> 2009-05-11 ?Doug Kwan ?<dougkwan@google.com>
>>
>> ? ? ? ?* tree-ssa-sccvn.c (compare_ops_1): Renamed from compare_ops.
>> ? ? ? ?(compare_ops): Wrapper for original compare_ops to stabilize qsort.
>>
>> Index: gcc/gcc/tree-ssa-sccvn.c
>> ===================================================================
>> --- gcc/gcc/tree-ssa-sccvn.c ? ?(revision 147396)
>> +++ gcc/gcc/tree-ssa-sccvn.c ? ?(working copy)
>> @@ -2411,7 +2411,7 @@ visit_use (tree use)
>> ?/* Compare two operands by reverse postorder index */
>>
>> ?static int
>> -compare_ops (const void *pa, const void *pb)
>> +compare_ops_1 (const void *pa, const void *pb)
>> ?{
>> ? const tree opa = *((const tree *)pa);
>> ? const tree opb = *((const tree *)pb);
>> @@ -2451,6 +2451,36 @@ compare_ops (const void *pa, const void
>> ? return rpo_numbers[bba->index] - rpo_numbers[bbb->index];
>> ?}
>>
>> +static int
>> +compare_ops (const void *pa, const void *pb)
>> +{
>> + ?const tree opa = *((const tree *)pa);
>> + ?const tree opb = *((const tree *)pb);
>> + ?unsigned HOST_WIDE_INT uid_a, uid_b;
>> + ?unsigned HOST_WIDE_INT ver_a, ver_b;
>> + ?int status = compare_ops_1 (pa, pb);
>> +
>> + ?if (status != 0)
>> + ? ?return status;
>> +
>> + ?/* Make qsort stable by doing addition comparisons. */
>> + ?uid_a = DECL_UID (SSA_NAME_VAR (opa));
>> + ?uid_b = DECL_UID (SSA_NAME_VAR (opb));
>> + ?if (uid_a < uid_b)
>> + ? ?return -1;
>> + ?else if (uid_a > uid_b)
>> + ? ?return 1;
>> +
>> + ?ver_a = SSA_NAME_VERSION (opa);
>> + ?ver_b = SSA_NAME_VERSION (opb);
>> + ?if (ver_a < ver_b)
>> + ? ?return -1;
>> + ?else if (ver_a > ver_b)
>> + ? ?return 1;
>> + ?else
>> + ? ?return 0;
>> +}
>> +
>> ?/* Sort an array containing members of a strongly connected component
>> ? ?SCC so that the members are ordered by RPO number.
>> ? ?This means that when the sort is complete, iterating through the
>>
>