[lra] take scratch as implicit unused output reloads [PR55212]

When trying to convert the SH port to use LRA, the first issue I hit
was the need for dealing with former scratch registers at places we
didn't need to on other ports, treating them like unused output
reloads instead of rejecting them.

for  gcc/ChangeLog

	PR target/55212
	* lra-constraints.cc (match_reload): Treat former scratch
	regs as implicit unused output reloads.
	(process_alt_operands): Likewise.
	(curr_insn_transform): Likewise.

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 66a300bf268bd3edb340e25b8a9711fa55141cc6..910f3fba8f4785587ec425d8ed86843dbff2e1a6 100644 (file)
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -1243,7 +1243,9 @@ match_reload (signed char out, signed char *ins, signed char *outs,
     return;
   /* See a comment for the input operand above.  */
   narrow_reload_pseudo_class (out_rtx, goal_class);
-  if (find_reg_note (curr_insn, REG_UNUSED, out_rtx) == NULL_RTX)
+  if (find_reg_note (curr_insn, REG_UNUSED, out_rtx) == NULL_RTX
+      && !ira_former_scratch_p (REGNO (SUBREG_P (out_rtx)
+                                      ? SUBREG_REG (out_rtx) : out_rtx)))
     {
       reg = SUBREG_P (out_rtx) ? SUBREG_REG (out_rtx) : out_rtx;
       start_sequence ();
@@ -3002,7 +3004,8 @@ process_alt_operands (int only_alternative)
                 objects with a REG_UNUSED note.  */
              if ((curr_static_id->operand[nop].type != OP_IN
                   && no_output_reloads_p
-                  && ! find_reg_note (curr_insn, REG_UNUSED, op))
+                  && ! find_reg_note (curr_insn, REG_UNUSED, op)
+                  && ! scratch_p)
                  || (curr_static_id->operand[nop].type != OP_OUT
                      && no_input_reloads_p && ! const_to_mem)
                  || (this_alternative_matches >= 0
@@ -3012,7 +3015,8 @@ process_alt_operands (int only_alternative)
                                  [this_alternative_matches].type != OP_IN)
                              && ! find_reg_note (curr_insn, REG_UNUSED,
                                                  no_subreg_reg_operand
-                                                 [this_alternative_matches])))))
+                                                 [this_alternative_matches])
+                             && ! scratch_p))))
                {
                  if (lra_dump_file != NULL)
                    fprintf
@@ -4856,7 +4860,8 @@ curr_insn_transform (bool check_only_p)
          if (type != OP_IN
              && find_reg_note (curr_insn, REG_UNUSED, old) == NULL_RTX
              /* OLD can be an equivalent constant here.  */
-             && !CONSTANT_P (old))
+             && !CONSTANT_P (old)
+             && !ira_former_scratch_p (REGNO (old)))
            {
              start_sequence ();
              lra_emit_move (type == OP_INOUT ? copy_rtx (old) : old, new_reg);