RISC-V: Fix dead loop for user vsetvli intrinsic avl checking [PR109773]

This patch is fix dead loop in vsetvl intrinsic avl checking.

vsetvli->get_def () has vsetvli->get_def () has vsetvli.....
Then it will keep looping in the vsetvli avl checking which is a dead loop.

	PR target/109773

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (avl_source_has_vsetvl_p): New function.
	(source_equal_p): Fix dead loop in vsetvl avl checking.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/vsetvl/pr109773-1.c: New test.
	* gcc.target/riscv/rvv/vsetvl/pr109773-2.c: New test.

1 files changed, 25 insertions, 0 deletions

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index d4d6f33..a69a418 100644
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -1057,6 +1057,24 @@ change_vsetvl_insn (const insn_info *insn, const vector_insn_info &info)
 }
 
 static bool
+avl_source_has_vsetvl_p (set_info *avl_source)
+{
+  if (!avl_source)
+    return false;
+  if (!avl_source->insn ())
+    return false;
+  if (avl_source->insn ()->is_real ())
+    return vsetvl_insn_p (avl_source->insn ()->rtl ());
+  hash_set<set_info *> sets = get_all_sets (avl_source, true, false, true);
+  for (const auto set : sets)
+    {
+      if (set->insn ()->is_real () && vsetvl_insn_p (set->insn ()->rtl ()))
+	return true;
+    }
+  return false;
+}
+
+static bool
 source_equal_p (insn_info *insn1, insn_info *insn2)
 {
   if (!insn1 || !insn2)
@@ -1098,6 +1116,13 @@ source_equal_p (insn_info *insn1, insn_info *insn2)
       vector_insn_info insn1_info, insn2_info;
       insn1_info.parse_insn (insn1);
       insn2_info.parse_insn (insn2);
+
+      /* To avoid dead loop, we don't optimize a vsetvli def has vsetvli
+	 instructions which will complicate the situation.  */
+      if (avl_source_has_vsetvl_p (insn1_info.get_avl_source ())
+	  || avl_source_has_vsetvl_p (insn2_info.get_avl_source ()))
+	return false;
+
       if (insn1_info.same_vlmax_p (insn2_info)
 	  && insn1_info.compatible_avl_p (insn2_info))
 	return true;