On 7/18/23 21:31, Jeff Law via Gcc-patches wrote:
In a run with -fno-fold-mem-offsets, the same insn 93 is successfully
grok'ed by cprop_hardreg,
| (insn 93 337 522 11 (set (mem/c:DF (plus:DI (reg/f:DI 2 sp)
| (const_int 8 [0x8])) [4 %sfp+-8 S8 A64])
| (const_double:DF 0.0 [0x0.0p+0])) "sff.i":23:11 190
{*movdf_hardfloat_rv64}
^^^^^^^^^^^^^^^
| (expr_list:REG_EQUAL (const_double:DF 0.0 [0x0.0p+0])
| (nil)))
P.S. I wonder if it is a good idea in general to call recog() post
reload since the insn could be changed sufficiently to no longer
match the md patterns. Of course I don't know the answer.
If this ever causes a problem, it's a backend bug. It's that simple.
Conceptually it should always be safe to set INSN_CODE to -1 for any
insn.
Sure the -1 should be handled, but are you implying that f-mo- will
always generate a valid combination and recog() failing is simply a bug
in backend and/or f-m-o. If not, the -1 setting can potentially trigger
an ICE in future.
Odds are for this specific case in the RV backend, we just need a
constraint to store 0.0 into a memory location. That can actually be
implemented as a store from x0 since 0.0 has the bit pattern 0x0.
This is probably a good thing to expose anyway as an optimization and
can move forward independently of the f-m-o patch.
I call dibs on this :-) Seems like an interesting little side project.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110748
-Vineet
