On Wed, Sep 14, 2016 at 03:08:21PM +0200, Bernd Schmidt wrote: > On 09/14/2016 03:04 PM, Segher Boessenkool wrote: > >Then rs6000 (and many other ports probably) will just turn it off again. > >It is actively harmful. > > The data that was posted showed a code size decrease on a number of > targets. I'm really not sure where this irrational hate for regrename > comes from.
It increases the number of active, "young" registers per thread. There is no irrational hate. Regrename is simply a de-optimisation on some (heavily) out-of-order targets. Not by much, but not a win either. We would rather do without it, on current CPUs at least (and I doubt this will change soon, but we'll see). (It also makes the generated code much harder to read, but you know that). Segher
