[PATCH] xtensa: Optimize inversion of the MSB

[PATCH] xtensa: Optimize inversion of the MSB

[Takayuki 'January June' Suwa]

Such operation can be done either bitwise-XOR or addition with -2147483648,
but the latter is one byte less if TARGET_DENSITY.

gcc/ChangeLog:

	* config/xtensa/xtensa.md (xorsi3_internal):
	Rename from the original of "xorsi3".
	(xorsi3): New expansion pattern that emits addition rather than
	bitwise-XOR when the second source is a constant of -2147483648
	if TARGET_DENSITY.
---
 gcc/config/xtensa/xtensa.md | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 0a477e711..4b5899a4c 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -736,7 +736,31 @@
    (set_attr "mode"	"SI")
    (set_attr "length"	"3")])
 
-(define_insn "xorsi3"
+(define_expand "xorsi3"
+  [(set (match_operand:SI 0 "register_operand")
+	(xor:SI (match_operand:SI 1 "register_operand")
+		(match_operand:SI 2 "nonmemory_operand")))]
+  ""
+{
+  if (register_operand (operands[2], SImode))
+    emit_insn (gen_xorsi3_internal (operands[0], operands[1],
+				    operands[2]));
+  else
+    {
+      rtx (*gen_op)(rtx, rtx, rtx);
+      if (TARGET_DENSITY
+	  && CONST_INT_P (operands[2])
+	  && INTVAL (operands[2]) == -2147483648L)
+	gen_op = gen_addsi3;
+      else
+	gen_op = gen_xorsi3_internal;
+      emit_insn (gen_op (operands[0], operands[1],
+			 force_reg (SImode, operands[2])));
+    }
+  DONE;
+})
+
+(define_insn "xorsi3_internal"
   [(set (match_operand:SI 0 "register_operand" "=a")
 	(xor:SI (match_operand:SI 1 "register_operand" "%r")
 		(match_operand:SI 2 "register_operand" "r")))]
-- 
2.30.2

Re: [PATCH] xtensa: Optimize inversion of the MSB

[Max Filippov]

On Tue, Jan 17, 2023 at 9:43 PM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> Such operation can be done either bitwise-XOR or addition with -2147483648,
> but the latter is one byte less if TARGET_DENSITY.
>
> gcc/ChangeLog:
>
>         * config/xtensa/xtensa.md (xorsi3_internal):
>         Rename from the original of "xorsi3".
>         (xorsi3): New expansion pattern that emits addition rather than
>         bitwise-XOR when the second source is a constant of -2147483648
>         if TARGET_DENSITY.
> ---
>  gcc/config/xtensa/xtensa.md | 26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)

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

-- 
Thanks.
-- Max