[gcc r13-5238] xtensa: Optimize inversion of the MSB

[Max Filippov <jcmvbkbc@gcc.gnu.org>]

https://gcc.gnu.org/g:a4b05944b7d409682197a9f50759a4ed97145e23

commit r13-5238-ga4b05944b7d409682197a9f50759a4ed97145e23
Author: Takayuki 'January June' Suwa <jjsuwa_sys3175@yahoo.co.jp>
Date:   Wed Jan 18 14:43:13 2023 +0900

    xtensa: Optimize inversion of the MSB
    
    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.

Diff:
---
 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 98f3c468f8b..dd3fc37353b 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")))]