[PATCH] xtensa: Eliminate double MEMW insertions for volatile memory

[PATCH] xtensa: Eliminate double MEMW insertions for volatile memory

[Takayuki 'January June' Suwa]

This patch makes avoid inserting a MEMW instruction before a load/store
nstruction with volatile memory reference if there is already a MEMW
immediately before it.

gcc/ChangeLog:

	* config/xtensa/xtensa.cc (print_operand):
	When outputting MEMW before the instruction, check if the previous
	instruction is already that.
---
  gcc/config/xtensa/xtensa.cc | 12 +++++++++++-
  1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/gcc/config/xtensa/xtensa.cc b/gcc/config/xtensa/xtensa.cc
index bc127997ac6..e2549de5df0 100644
--- a/gcc/config/xtensa/xtensa.cc
+++ b/gcc/config/xtensa/xtensa.cc
@@ -3078,7 +3078,17 @@ print_operand (FILE *file, rtx x, int letter)
  	  /* For a volatile memory reference, emit a MEMW before the
  	     load or store.  */
  	  if (MEM_VOLATILE_P (x) && TARGET_SERIALIZE_VOLATILE)
-	    fprintf (file, "memw\n\t");
+	    {
+	      rtx_insn *prev_insn
+			= prev_nonnote_nondebug_insn (current_output_insn);
+	      rtx pat, src;
+
+	      if (! (prev_insn && NONJUMP_INSN_P (prev_insn)
+		     && GET_CODE (pat = PATTERN (prev_insn)) == SET
+		     && GET_CODE (src = SET_SRC (pat)) == UNSPEC
+		     && XINT (src, 1) == UNSPEC_MEMW))
+		fprintf (file, "memw\n\t");
+	    }
  	}
        else
  	output_operand_lossage ("invalid %%v value");
-- 
2.39.2

Re: [PATCH] xtensa: Eliminate double MEMW insertions for volatile memory

[Max Filippov]

On Tue, Jun 18, 2024 at 10:00 PM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> This patch makes avoid inserting a MEMW instruction before a load/store
> nstruction with volatile memory reference if there is already a MEMW
> immediately before it.
>
> gcc/ChangeLog:
>
>         * config/xtensa/xtensa.cc (print_operand):
>         When outputting MEMW before the instruction, check if the previous
>         instruction is already that.
> ---
>   gcc/config/xtensa/xtensa.cc | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)

Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.

-- 
Thanks.
-- Max