RISC-V: Use biggest_mode as mode for constants.

In compute_nregs_for_mode we expect that the current variable's mode is
at most as large as the biggest mode to be used for vectorization.

This might not be true for constants as they don't actually have a mode.
In that case, just use the biggest mode so max_number_of_live_regs
returns 1.

This fixes several test cases in the test suite.

gcc/ChangeLog:

	PR target/116655

	* config/riscv/riscv-vector-costs.cc (max_number_of_live_regs):
	Use biggest mode instead of constant's saved mode.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/pr116655.c: New test.

1 files changed, 10 insertions, 4 deletions

diff --git a/gcc/config/riscv/riscv-vector-costs.cc b/gcc/config/riscv/riscv-vector-costs.cc
index 25570bd..67b9e3e 100644
--- a/gcc/config/riscv/riscv-vector-costs.cc
+++ b/gcc/config/riscv/riscv-vector-costs.cc
@@ -194,7 +194,7 @@ compute_local_program_points (
       /* Collect the stmts that is vectorized and mark their program point.  */
       for (i = 0; i < nbbs; i++)
 	{
-	  int point = 1;
+	  unsigned int point = 1;
 	  basic_block bb = bbs[i];
 	  vec<stmt_point> program_points = vNULL;
 	  if (dump_enabled_p ())
@@ -489,9 +489,15 @@ max_number_of_live_regs (loop_vec_info loop_vinfo, const basic_block bb,
       pair live_range = (*iter).second;
       for (i = live_range.first + 1; i <= live_range.second; i++)
 	{
-	  machine_mode mode = TREE_CODE (TREE_TYPE (var)) == BOOLEAN_TYPE
-				? BImode
-				: TYPE_MODE (TREE_TYPE (var));
+	  machine_mode mode;
+	  if (TREE_CODE (TREE_TYPE (var)) == BOOLEAN_TYPE)
+	    mode = BImode;
+	  /* Constants do not have a mode, just use the biggest so
+	     compute_nregs will return 1.  */
+	  else if (TREE_CODE (var) == INTEGER_CST)
+	    mode = biggest_mode;
+	  else
+	    mode = TYPE_MODE (TREE_TYPE (var));
 	  unsigned int nregs
 	    = compute_nregs_for_mode (loop_vinfo, mode, biggest_mode, lmul);
 	  live_vars_vec[i] += nregs;