RISC-V: Fix VSETLV PASS compile-time issue

RISC-V: Fix VSETLV PASS compile-time issue

The compile time issue was discovered in SPEC 2017 wrf:

Use time and -ftime-report to analyze the profile data of SPEC 2017 wrf compilation .

Before this patch (Lazy vsetvl):

scheduling                         : 121.89 ( 15%)   0.53 ( 11%) 122.72 ( 15%)    13M (  1%)
machine dep reorg                  : 424.61 ( 53%)   1.84 ( 37%) 427.44 ( 53%)  5290k (  0%)
real    13m27.074s
user    13m19.539s
sys     0m5.180s

Simple vsetvl:

machine dep reorg                  :   0.10 (  0%)   0.00 (  0%)   0.11 (  0%)  4138k (  0%)
real    6m5.780s
user    6m2.396s
sys     0m2.373s

The machine dep reorg is the compile time of VSETVL PASS (424 seconds) which counts 53% of
the compilation time, spends much more time than scheduling.

After investigation, the critical patch of VSETVL pass is compute_lcm_local_properties which
is called every iteration of phase 2 (earliest fusion) and phase 3 (global lcm).

This patch optimized the codes of compute_lcm_local_properties to reduce the compilation time.

After this patch:

scheduling                         : 117.51 ( 27%)   0.21 (  6%) 118.04 ( 27%)    13M (  1%)
machine dep reorg                  :  80.13 ( 18%)   0.91 ( 26%)  81.26 ( 18%)  5290k (  0%)
real    7m25.374s
user    7m20.116s
sys     0m3.795s

The optimization of this patch is very obvious, lazy VSETVL PASS: 424s (53%) -> 80s (18%) which
spend less time than scheduling.

Tested on both RV32 and RV64 no regression.  Ok for trunk ?

	PR target/113495

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (extract_single_source): Remove.
	(pre_vsetvl::compute_vsetvl_def_data): Fix compile time issue.
	(pre_vsetvl::compute_transparent): New function.
	(pre_vsetvl::compute_lcm_local_properties): Fix compile time time issue.