VAX: Fix predicates for widening multiply and multiply-add insns

VAX: Fix predicates for widening multiply and multiply-add insns

It makes no sense for insn operand predicates, as long as they accept a
register operand, to be more restrictive than the set of the associated
constraints, because expand will choose the insn based on the relevant
operand being a pseudo register then and reload will keep it happily as
an immediate if a constraint permits it.  So the restriction posed by
such a predicate will be happily ignored, and moreover if a splitter is
added, such as required for MODE_CC support, the new instructions will
reject the original operands supplied, causing an ICE like below:

.../gcc/testsuite/gfortran.dg/graphite/PR67518.f90:44:0: Error: could not split insn
(insn 90 662 663 (set (reg:DI 10 %r10 [orig:97 _235 ] [97])
        (mult:DI (sign_extend:DI (mem/c:SI (plus:SI (reg/f:SI 13 %fp)
                        (const_int -800 [0xfffffffffffffce0])) [14 %sfp+-800 S4 A32]))
            (sign_extend:DI (const_int -51 [0xffffffffffffffcd])))) 299 {mulsidi3}
     (expr_list:REG_EQUAL (mult:DI (sign_extend:DI (subreg:SI (mem/c:DI (plus:SI (reg/f:SI 13 %fp)
                            (const_int -800 [0xfffffffffffffce0])) [14 %sfp+-800 S8 A32]) 0))
            (const_int -51 [0xffffffffffffffcd]))
        (nil)))
during RTL pass: final
.../gcc/testsuite/gfortran.dg/graphite/PR67518.f90:44:0: internal compiler error: in final_scan_insn_1, at final.c:3073
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://gcc.gnu.org/bugs/> for instructions.

Change the predicates used with the widening multiply and multiply-add
insns to allow immediates then, just as the constraints and the machine
instructions produced permit.

Also give the insns names, for easier reference here and elsewhere.

	gcc/
	* config/vax/vax.md (mulsidi3): Fix the multiplicand predicates.
	(*maddsidi4, *maddsidi4_const): Likewise.  Name insns.