On 6/14/24 11:10 AM, Alexander Monakov wrote:
On Fri, 14 Jun 2024, Kong, Lingling wrote:
APX CFCMOV[1] feature implements conditionally faulting which means that all
memory faults are suppressed
when the condition code evaluates to false and load or store a memory operand.
Now we could load or store a
memory operand may trap or fault for conditional move.
In middle-end, now we don't support a conditional move if we knew that a load
from A or B could trap or fault.
Predicated loads&stores on Itanium don't trap either. They are modeled via
COND_EXEC on RTL. The late if-conversion pass (the instance that runs after
reload) is capable of introducing them.
To enable CFCMOV, we add a target HOOK TARGET_HAVE_CONDITIONAL_MOVE_MEM_NOTRAP
in if-conversion pass to allow convert to cmov.
Considering the above, is the new hook really necessary? Can you model the new
instructions via (cond_exec () (set ...)) instead of (set (if_then_else ...)) ?
Note that turning on cond_exec will turn off some of the cmove support.
But the general suggesting of trying to avoid a hook for this is a good
one. In fact, my first reaction to this thread was "do we really need a
hook for this".
jeff
