[Committed] RISC-V: Fix PR112888 ICE

[Juzhe-Zhong]

Committed as it is ovbious.

gcc/ChangeLog:

        * config/riscv/riscv-vsetvl.cc (extract_single_source): new function.
        (pre_vsetvl::compute_lcm_local_properties): Fix ICE.

---
 gcc/config/riscv/riscv-vsetvl.cc | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index 68f0be7e81d..90477f331d7 100644
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -596,6 +596,14 @@ extract_single_source (set_info *set)
   return first_insn;
 }
 
+static insn_info *
+extract_single_source (def_info *def)
+{
+  if (!def)
+    return nullptr;
+  return extract_single_source (dyn_cast<set_info *> (def));
+}
+
 static bool
 same_equiv_note_p (set_info *set1, set_info *set2)
 {
@@ -2692,9 +2700,7 @@ pre_vsetvl::compute_lcm_local_properties ()
                          def_lookup dl = crtl->ssa->find_def (resource, insn);
                          def_info *def
                            = dl.matching_set_or_last_def_of_prev_group ();
-                         gcc_assert (def);
-                         insn_info *def_insn = extract_single_source (
-                           dyn_cast<set_info *> (def));
+                         insn_info *def_insn = extract_single_source (def);
                          if (def_insn && vsetvl_insn_p (def_insn->rtl ()))
                            {
                              vsetvl_info def_info = vsetvl_info (def_insn);
-- 
2.36.3