RISC-V: Make liveness be aware of rgroup number of LENS[dynamic LMUL]

RISC-V: Make liveness be aware of rgroup number of LENS[dynamic LMUL]

This patch fixes the following situation:
vl4re16.v       v12,0(a5)
...
vl4re16.v       v16,0(a3)
vs4r.v  v12,0(a5)
...
vl4re16.v       v4,0(a0)
vs4r.v  v16,0(a3)
...
vsetvli a3,zero,e16,m4,ta,ma
...
vmv.v.x v8,t6
vmsgeu.vv       v2,v16,v8
vsub.vv v16,v16,v8
vs4r.v  v16,0(a5)
...
vs4r.v  v4,0(a0)
vmsgeu.vv       v1,v4,v8
...
vsub.vv v4,v4,v8
slli    a6,a4,2
vs4r.v  v4,0(a5)
...
vsub.vv v4,v12,v8
vmsgeu.vv       v3,v12,v8
vs4r.v  v4,0(a5)
...

There are many spills which are 'vs4r.v'.  The root cause is that we don't count
vector REG liveness referencing the rgroup controls.

_29 = _25->iatom[0]; is transformed into the following vect statement with 4 different loop_len (loop_len_74, loop_len_75, loop_len_76, loop_len_77).

  vect__29.11_78 = .MASK_LEN_LOAD (vectp_sb.9_72, 32B, { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }, loop_len_74, 0);
  vect__29.12_80 = .MASK_LEN_LOAD (vectp_sb.9_79, 32B, { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }, loop_len_75, 0);
  vect__29.13_82 = .MASK_LEN_LOAD (vectp_sb.9_81, 32B, { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }, loop_len_76, 0);
  vect__29.14_84 = .MASK_LEN_LOAD (vectp_sb.9_83, 32B, { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }, loop_len_77, 0);

which are the LENS number (LOOP_VINFO_LENS (loop_vinfo).length ()).

Count liveness according to LOOP_VINFO_LENS (loop_vinfo).length () to compute liveness more accurately:

vsetivli	zero,8,e16,m1,ta,ma
vmsgeu.vi	v19,v14,8
vadd.vi	v18,v14,-8
vmsgeu.vi	v17,v1,8
vadd.vi	v16,v1,-8
vlm.v	v15,0(a5)
...

Tested no regression, ok for trunk ?

	PR target/113112

gcc/ChangeLog:

	* config/riscv/riscv-vector-costs.cc (compute_nregs_for_mode): Add rgroup info.
	(max_number_of_live_regs): Ditto.
	(has_unexpected_spills_p): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/costmodel/riscv/rvv/pr113112-5.c: New test.