RISC-V: Handle 0.0 floating point pattern costing to match const_vector expander

The comment previously here stated that the Wc0/Wc1 cases are handled by
the vi constraint but that is not true for the 0.0 Wc0 case.

gcc/ChangeLog:

	* config/riscv/riscv-v.h (valid_vec_immediate_p): Add new helper.
	* config/riscv/riscv-v.cc (valid_vec_immediate_p): Ditto.
	(expand_const_vector): Use new helper.
	* config/riscv/riscv.cc (riscv_const_insns): Handle 0.0 floating-point
	case.

Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>

gcc/config/riscv/riscv-v.cc

@@ -794,6 +794,15 @@ const_vec_all_in_range_p (rtx vec, poly_int64 minval, poly_int64 maxval)
   return true;
 }
 
+/* Returns true if the vector's elements are all duplicates in
+   range -16 ~ 15 integer or 0.0 floating-point.  */
+
+bool
+valid_vec_immediate_p (rtx x)
+{
+  return (satisfies_constraint_vi (x) || satisfies_constraint_Wc0 (x));
+}
+
 /* Return a const vector of VAL. The VAL can be either const_int or
    const_poly_int.  */
 
@@ -1119,7 +1128,7 @@ expand_const_vector (rtx target, rtx src)
     {
       /* Element in range -16 ~ 15 integer or 0.0 floating-point,
 	 we use vmv.v.i instruction.  */
-      if (satisfies_constraint_vi (src) || satisfies_constraint_Wc0 (src))
+      if (valid_vec_immediate_p (src))
 	{
 	  rtx ops[] = {result, src};
 	  emit_vlmax_insn (code_for_pred_mov (mode), UNARY_OP, ops);

gcc/config/riscv/riscv-v.h

@@ -83,6 +83,8 @@ private:
   unsigned int m_inner_bytes_size;
 };
 
+extern bool valid_vec_immediate_p(rtx);
+
 } // namespace riscv_vector
 
 #endif // GCC_RISCV_V_H

gcc/config/riscv/riscv.cc

@@ -2158,11 +2158,9 @@ riscv_const_insns (rtx x, bool allow_new_pseudos)
 		if (maybe_gt (GET_MODE_SIZE (smode), UNITS_PER_WORD)
 		    && !immediate_operand (elt, Pmode))
 		  return 0;
-		/* Constants from -16 to 15 can be loaded with vmv.v.i.
-		   The Wc0, Wc1 constraints are already covered by the
-		   vi constraint so we do not need to check them here
-		   separately.  */
-		if (satisfies_constraint_vi (x))
+		/* Constants in range -16 ~ 15 integer or 0.0 floating-point
+		   can be emitted using vmv.v.i.  */
+		if (valid_vec_immediate_p (x))
 		  return 1;
 
 		/* Any int/FP constants can always be broadcast from a