https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102224
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org
Status|NEW |ASSIGNED
--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 51422
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51422&action=edit
gcc12-pr102224.patch
Untested fix. It is actually a mess.
While we can during expansion emit efficient fabs code if the two input
operands are equal, we still need to ensure correctness for the case where the
operand equality is discovered only after expansion.
This patch does that by ensuring through early-clobber and constraints that
for pre-AVX dest==op1 is different from op0, because we want to overwrite op1
first with op1 & mask before using op0. For AVX, the constraints ensure that
either all of dest, op0 and op1 are different, or any two of them are the same
but the third one is different. If op0 and op1 are different, then it is ok
without further changes, the i386-expand.c changes are for the op0 == op1 case
where we've ensured that dest is different from the inputs - we can emit vpandn
but if the mask is in memory, we need to force it into a register and can use
dest for that.
