From: Takayuki 'January June' Suwa <jjsuwa_sys3175@yahoo.co.jp>
Date: Fri, 31 Oct 2025 06:23:15 +0000 (+0900)
Subject: xtensa: Add alternative negsf2 insn pattern
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=806b229561f5380c00057c16bc1644dbf58cfa9b;p=thirdparty%2Fgcc.git

xtensa: Add alternative negsf2 insn pattern

If both the source and destination are address (GP) registers, emitting
instructions that invert the MSB of the address register is two bytes
shorter if TARGET_DENSITY is enabled than emitting a NEG.S machine inst-
ruction that uses hardware FP registers with two reloads.

     /* example */
     float test(float a) {
       return -a;
     }

     ;; before
     test:
     	entry	sp, 32
     	wfr	f0, a2
     	neg.s	f0, f0
     	rfr	a2, f0
     	retw.n

     ;; after
     test:
     	entry	sp, 32
     	movi.n	a8, 1
     	slli	a8, a8, 31
     	add.n	a2, a2, a8
     	retw.n

By the way, in configurations that do not use hardware FP register, the
RTL expansion pass will emit such insns by default.

gcc/ChangeLog:

	* config/xtensa/xtensa.md (negsf2):
	Add another insn pattern that is valid when TARGET_DENSITY is
	enabled and both the source and destination are address registers.
---

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 7dc941f9571..c713451951c 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -695,13 +695,15 @@
 })
 
 (define_insn "negsf2"
-  [(set (match_operand:SF 0 "register_operand" "=f")
-	(neg:SF (match_operand:SF 1 "register_operand" "f")))]
+  [(set (match_operand:SF 0 "register_operand")
+        (neg:SF (match_operand:SF 1 "register_operand")))
+   (clobber (match_scratch:SI 2))]
   "TARGET_HARD_FLOAT"
-  "neg.s\t%0, %1"
-  [(set_attr "type"	"farith")
-   (set_attr "mode"	"SF")
-   (set_attr "length"	"3")])
+  {@ [cons: =0, 1, =2; attrs: type, length]
+     [D, D, &a; arith , 7] movi.n\t%2, 1\;slli\t%2, %2, 31\;add.n\t%0, %1, %2
+     [f, f,  X; farith, 3] neg.s\t%0, %1
+  }
+  [(set_attr "mode" "SF")])
 
 
 ;; Logical instructions.