[gcc r13-5120] xtensa: Tune "*btrue" insn pattern

[gcc r13-5120] xtensa: Tune "*btrue" insn pattern

[Max Filippov]

https://gcc.gnu.org/g:bb65bd084a8739feb5b85f87135c531fc8b86572

commit r13-5120-gbb65bd084a8739feb5b85f87135c531fc8b86572
Author: Takayuki 'January June' Suwa <jjsuwa_sys3175@yahoo.co.jp>
Date:   Thu Jan 12 13:25:58 2023 +0900

    xtensa: Tune "*btrue" insn pattern
    
    This branch instruction has short encoding if EQ/NE comparison against
    immediate zero when the Code Density Option is enabled, but its "length"
    attribute was only for normal encoding.  This patch fixes it.
    
    This patch also prevents undesireable replacement the comparison immediate
    zero of the instruction (short encoding, as mentioned above) with a
    register that has value of zero (normal encoding) by the postreload pass.
    
    gcc/ChangeLog:
    
            * config/xtensa/xtensa.md (*btrue):
            Correct value of the attribute "length" that depends on
            TARGET_DENSITY and operands, and add '?' character to the register
            constraint of the compared operand.

Diff:
---
 gcc/config/xtensa/xtensa.md | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index db1d68ee658..b4989832169 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -1679,7 +1679,7 @@
   [(set (pc)
 	(if_then_else (match_operator 3 "branch_operator"
 			[(match_operand:SI 0 "register_operand" "r,r")
-			 (match_operand:SI 1 "branch_operand" "K,r")])
+			 (match_operand:SI 1 "branch_operand" "K,?r")])
 		      (label_ref (match_operand 2 "" ""))
 		      (pc)))]
   ""
@@ -1688,7 +1688,14 @@
 }
   [(set_attr "type"	"jump,jump")
    (set_attr "mode"	"none")
-   (set_attr "length"	"3,3")])
+   (set (attr "length")
+        (if_then_else (match_test "TARGET_DENSITY
+				   && CONST_INT_P (operands[1])
+				   && INTVAL (operands[1]) == 0
+				   && (GET_CODE (operands[3]) == EQ
+				       || GET_CODE (operands[3]) == NE)")
+                      (const_int 2)
+                      (const_int 3)))])
 
 (define_insn "*ubtrue"
   [(set (pc)