On Fri, Mar 4, 2016 at 12:49 PM, Bernd Schmidt <bschm...@redhat.com> wrote:
> On 03/04/2016 06:27 PM, Bernd Schmidt wrote:
>>
>> On 03/04/2016 06:14 PM, Patrick Palka wrote:
>>
>>> I just quickly tested building the generated insn-attrtab.c with and
>>> without the patch using my host gcc 5.3 compiler and the .s output is
>>> not the same.
>>
>>
>> Hmm, looking at the 003t.original dump it looks like there are
>> differences in SAVE_EXPRs. Indeed we seem to generate different code for
>>
>> int at;
>>
>> int foo ()
>> {
>> if (at == 2 || at == 4 || at == 7)
>> return 1;
>> return 0;
>> }
>>
>> int bar ()
>> {
>> if (at == 2 || (at == 4 || at == 7))
>> return 1;
>> return 0;
>> }
>
>
> Ahh... it's not just different placement of SAVE_EXPRs, it's actually a case
> of TRUTH_ORIF_EXPR vs. TRUTH_OR_EXPR (the distinction is invisible in the
> dumps), the latter being created by fold_range_test. That's a bit of a
> broken optimization what with its inability to see more than two comparisons
> at a time... we convert one ORIF per function, but a different one.
>
>
> Bernd
I've filed PR c/70087, https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70087
