https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70243
Segher Boessenkool <segher at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
Priority|P3 |P1
--- Comment #6 from Segher Boessenkool <segher at gcc dot gnu.org> ---
We should not use any VMX insn unless explicitly asked for it, since those
do not work as expected if VSCR[NJ]=1, which unfortunately is the default on
Linux (but not on powerpc64le-linux; that is a separate (kernel) bug).
Rounding mode does not matter too much, if we have some subset of fast-math
anyway; the only rounding mode in VMX is round-to-nearest-ties-to-even, which
is the default for most everything else).
But NJ=1 makes arithmetic behave completely unexpectedly, and it isn't
actually faster than NJ=0 on modern hardware anyway. We cannot change the
default for setting NJ because some code might rely on it, unfortunately.
Luckily disabling generating all VMX insns automatically (i.e. without it
being explicitly asked for) isn't all that expensive, just ends up as a few
more move instructions here and there.
This isn't a regression, but we should have this in GCC 13.
