RISC-V: Fix large memory usage of VSETVL PASS [PR113495]

RISC-V: Fix large memory usage of VSETVL PASS [PR113495]

SPEC 2017 wrf benchmark expose unreasonble memory usage of VSETVL PASS
that is, VSETVL PASS consume over 33 GB memory which make use impossible
to compile SPEC 2017 wrf in a laptop.

The root cause is wasting-memory variables:

unsigned num_exprs = num_bbs * num_regs;
sbitmap *avl_def_loc = sbitmap_vector_alloc (num_bbs, num_exprs);
sbitmap *m_kill = sbitmap_vector_alloc (num_bbs, num_exprs);
m_avl_def_in = sbitmap_vector_alloc (num_bbs, num_exprs);
m_avl_def_out = sbitmap_vector_alloc (num_bbs, num_exprs);

I find that compute_avl_def_data can be achieved by RTL_SSA framework.
Replace the code implementation base on RTL_SSA framework.

After this patch, the memory-hog issue is fixed.

simple vsetvl memory usage (valgrind --tool=massif --pages-as-heap=yes --massif-out-file=massif.out)
is 1.673 GB.

lazy vsetvl memory usage (valgrind --tool=massif --pages-as-heap=yes --massif-out-file=massif.out)
is 2.441 GB.

Tested on both RV32 and RV64, no regression.

gcc/ChangeLog:

	PR target/113495
	* config/riscv/riscv-vsetvl.cc (get_expr_id): Remove.
	(get_regno): Ditto.
	(get_bb_index): Ditto.
	(pre_vsetvl::compute_avl_def_data): Ditto.
	(pre_vsetvl::earliest_fuse_vsetvl_info): Fix large memory usage.
	(pre_vsetvl::pre_global_vsetvl_info): Ditto.

gcc/testsuite/ChangeLog:

	PR target/113495
	* gcc.target/riscv/rvv/vsetvl/avl_single-107.c: Adapt test.