[gcc r14-351] reload: Handle generating reloads that also clobbers flags

[Hans-Peter Nilsson <hp@gcc.gnu.org>]

https://gcc.gnu.org/g:7eefdc9c77892b679d183c1154ebb567251f0964

commit r14-351-g7eefdc9c77892b679d183c1154ebb567251f0964
Author: Hans-Peter Nilsson <hp@axis.com>
Date:   Mon Feb 13 23:10:24 2023 +0100

    reload: Handle generating reloads that also clobbers flags
    
            * reload1.cc (emit_insn_if_valid_for_reload_1): Rename from
            emit_insn_if_valid_for_reload.
            (emit_insn_if_valid_for_reload): Call new helper, and if a SET fails
            to be recognized, also try emitting a parallel that clobbers
            TARGET_FLAGS_REGNUM, as applicable.

Diff:
---
 gcc/reload1.cc | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/gcc/reload1.cc b/gcc/reload1.cc
index 7dcef50437b..9ec2cb9baf4 100644
--- a/gcc/reload1.cc
+++ b/gcc/reload1.cc
@@ -8377,11 +8377,11 @@ emit_reload_insns (class insn_chain *chain)
   reg_reloaded_dead |= reg_reloaded_died;
 }
 \f
-/* Go through the motions to emit INSN and test if it is strictly valid.
-   Return the emitted insn if valid, else return NULL.  */
+
+/* Helper for emit_insn_if_valid_for_reload.  */
 
 static rtx_insn *
-emit_insn_if_valid_for_reload (rtx pat)
+emit_insn_if_valid_for_reload_1 (rtx pat)
 {
   rtx_insn *last = get_last_insn ();
   int code;
@@ -8403,6 +8403,29 @@ emit_insn_if_valid_for_reload (rtx pat)
   return NULL;
 }
 
+/* Go through the motions to emit INSN and test if it is strictly valid.
+   Return the emitted insn if valid, else return NULL.  */
+
+static rtx_insn *
+emit_insn_if_valid_for_reload (rtx pat)
+{
+  rtx_insn *insn = emit_insn_if_valid_for_reload_1 (pat);
+
+  if (insn)
+    return insn;
+
+  /* If the pattern is a SET, and this target has a single
+     flags-register, try again with a PARALLEL that clobbers that
+     register.  */
+  if (targetm.flags_regnum == INVALID_REGNUM || GET_CODE (pat) != SET)
+    return NULL;
+
+  rtx flags_clobber = gen_hard_reg_clobber (CCmode, targetm.flags_regnum);
+  rtx parpat = gen_rtx_PARALLEL (VOIDmode, gen_rtvec (2, pat, flags_clobber));
+
+  return emit_insn_if_valid_for_reload (parpat);
+}
+
 /* Emit code to perform a reload from IN (which may be a reload register) to
    OUT (which may also be a reload register).  IN or OUT is from operand
    OPNUM with reload type TYPE.