[Bug target/79185] [4.9/5/6/7 Regression] register allocation in the addition of two 128 bit ints

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79185

Marc Glisse <glisse at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-01-22
      Known to work|                            |4.8.4
            Summary|Possible regression in gcc  |[4.9/5/6/7 Regression]
                   |4.9 and later with the      |register allocation in the
                   |addition of two 128 bit     |addition of two 128 bit
                   |ints                        |ints
     Ever confirmed|0                           |1
      Known to fail|                            |4.9.2, 5.4.0, 6.2.0

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
Yes, gcc's register allocator tends to be suboptimal near function boundaries
(handling the hard registers for input/output) and more attention was paid to
optimizing the interior of functions (after sufficient inlining, the rest is
usually negligible). There are several related PRs in bugzilla. Still, it would
be nice to improve this...