On 01/29/2016 10:34 AM, Bernd Schmidt wrote:
So PR57193 has an example of sub-optimal code generation, with some
unnecessary register moves left after LRA. These seem to be difficult to
prevent, but last year Robert Suchanek made some modifications to
regrename that allow it to clean up such cases. Enabling
-frename-registers removes one of the two unnecessary copies, and I'm
pretty sure I could make it eliminate the other one as well with a bit
more work.
Hence, this patch. The renamer has seen a lot of fixes over the years
and should be in pretty good shape IMO. Still, I won't deny that this is
a bit riskier than the usual bugfix patch at this stage.
Bootstrapped and tested on x86_64-linux, with my earlier patch to fix
some i386 tests. Thoughts? Should we do this for gcc-7 at least?
invoke.texi has an independent list (probably incomplete! ;( of all the
things that -O2 enables. Make sure to add -frename-registers to that
list and this is Ok for the trunk (gcc-7).
jeff
