[Bug tree-optimization/77980] Regression in GCC-7.0.0's optimizer.

2016-10-14 Thread glisse at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77980

--- Comment #3 from Marc Glisse  ---
Note that "regression in gcc-7.0.0" would mean that gcc-6 was doing better,
which is not the case.

[Bug tree-optimization/77980] Regression in GCC-7.0.0's optimizer.

2016-10-14 Thread marxin at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77980

Martin Liška  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2016-10-14
 CC||marxin at gcc dot gnu.org
 Ever confirmed|0   |1

--- Comment #2 from Martin Liška  ---
Confirmed.

[Bug tree-optimization/77980] Regression in GCC-7.0.0's optimizer.

2016-10-13 Thread glisse at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77980

--- Comment #1 from Marc Glisse  ---
To simplify 1/n to 0, we would have to notice that n cannot be ±1 (the last bit
is zero since n is 2*x2), and it cannot be 0 either in that division. That
seems quite specialized, but rather easy to add to match.pd using
get_nonzero_bits if someone wants to write it... Is there anything more general
that can be done based on that?