[PATCH][GCC 13] RISC-V: Fix recursive vsetvli checking [PR114172]

[Kito Cheng <kito.cheng@sifive.com>]

extract_single_source will recursive checking the sources to
make sure if it's single source, however it may cause infinite
recursive when the source is come from itself, so it should just skip
first source to prevent that.

NOTE: This logic has existing on trunk/GCC 14, but it included in a big
vsetvli improvement patch, which is not backport to GCC 13.

```

void saxpy_rvv_m8(float *y, long vl)
{
    for (;;)
    {
        vl = __riscv_vsetvl_e32m8(vl); //ICE
        vfloat32m8_t y_vec;
        __riscv_vse32_v_f32m8(y, y_vec, vl);
    }
}
```

gcc/ChangeLog:

	PR target/114172
	* gcc/config/riscv/riscv-vsetvl.cc (extract_single_source):
	Skip first set.

gcc/testsuite/ChangeLog:

	PR target/114172
	* gcc.target/riscv/rvv/vsetvl/pr114172.c: New.
---
 gcc/config/riscv/riscv-vsetvl.cc                   |  4 ++++
 .../gcc.target/riscv/rvv/vsetvl/pr114172.c         | 14 ++++++++++++++
 2 files changed, 18 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr114172.c

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index 9dca2ce709d..36d2e6e6f20 100644
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -1196,6 +1196,10 @@ extract_single_source (set_info *set)
     return nullptr;
   for (const set_info *set : sets)
     {
+      /* Skip first set, this can prevent us run into infinite recursive
+	 checking if first set is come from itself.  */
+      if (set == *sets.begin ())
+	continue;
       /* If there is a head or end insn, we conservative return
 	 NULL so that VSETVL PASS will insert vsetvl directly.  */
       if (set->insn ()->is_artificial ())
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr114172.c b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr114172.c
new file mode 100644
index 00000000000..ed1494666d6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr114172.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64 -fno-tree-vectorize" } */
+
+#include "riscv_vector.h"
+
+void e(long, vfloat32m4_t);
+
+void b(long c) {
+  for (;;) {
+    c = __riscv_vsetvl_e32m4(c);
+    vfloat32m4_t d;
+    e(c, d);
+  }
+}
-- 
2.34.1