[gcc r14-2065] i386: Add alternate representation for {and, or, xor}b %ah, %dh.

[gcc r14-2065] i386: Add alternate representation for {and, or, xor}b %ah, %dh.

[Roger Sayle]

https://gcc.gnu.org/g:8f6c747c8638d4c3c47ba2d4c8be86909e183132

commit r14-2065-g8f6c747c8638d4c3c47ba2d4c8be86909e183132
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Sat Jun 24 23:05:25 2023 +0100

    i386: Add alternate representation for {and,or,xor}b %ah,%dh.
    
    A patch that I'm working on to improve RTL simplifications in the
    middle-end results in the regression of pr78904-1b.c, due to changes in
    the canonical representation of high-byte (%ah, %bh, %ch, %dh) logic.
    See also PR target/78904.
    
    This patch avoids/prevents those failures by adding support for the
    alternate representation, duplicating the existing *<code>qi_ext<mode>_2
    as *<code>qi_ext<mode>_3 (the new version also replacing any_or with
    any_logic to provide *andqi_ext<mode>_3 in the same pattern).  Removing
    the original pattern isn't trivial, as it's generated by define_split,
    but this can be investigated after the other pieces are approved.
    
    The current representation of this instruction is:
    
    (set (zero_extract:DI (reg/v:DI 87 [ aD.2763 ])
            (const_int 8 [0x8])
            (const_int 8 [0x8]))
        (subreg:DI (xor:QI (subreg:QI (zero_extract:DI (reg:DI 94)
                        (const_int 8 [0x8])
                        (const_int 8 [0x8])) 0)
                (subreg:QI (zero_extract:DI (reg/v:DI 87 [ aD.2763 ])
                        (const_int 8 [0x8])
                        (const_int 8 [0x8])) 0)) 0))
    
    after my proposed middle-end improvement, we attempt to recognize:
    
    (set (zero_extract:DI (reg/v:DI 87 [ aD.2763 ])
            (const_int 8 [0x8])
            (const_int 8 [0x8]))
        (zero_extract:DI (xor:DI (reg:DI 94)
                (reg/v:DI 87 [ aD.2763 ]))
            (const_int 8 [0x8])
            (const_int 8 [0x8])))
    
    2023-06-24  Roger Sayle  <roger@nextmovesoftware.com>
    
    gcc/ChangeLog
            * config/i386/i386.md (*<code>qi_ext<mode>_3): New define_insn.

Diff:
---
 gcc/config/i386/i386.md | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 95a6653cd13..b50d82bf768 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -11380,6 +11380,8 @@
   [(set_attr "type" "alu")
    (set_attr "mode" "QI")])
 
+;; *andqi_ext<mode>_3 is defined via *<code>qi_ext<mode>_3 below.
+
 ;; Convert wide AND instructions with immediate operand to shorter QImode
 ;; equivalents when possible.
 ;; Don't do the splitting with memory operands, since it introduces risk
@@ -12092,6 +12094,26 @@
   [(set_attr "type" "alu")
    (set_attr "mode" "QI")])
 
+(define_insn "*<code>qi_ext<mode>_3"
+  [(set (zero_extract:SWI248
+	  (match_operand 0 "int248_register_operand" "+Q")
+	  (const_int 8)
+	  (const_int 8))
+	(zero_extract:SWI248
+	  (any_logic:SWI248
+	    (match_operand 1 "int248_register_operand" "%0")
+	    (match_operand 2 "int248_register_operand" "Q"))
+	  (const_int 8)
+	  (const_int 8)))
+   (clobber (reg:CC FLAGS_REG))]
+  "(!TARGET_PARTIAL_REG_STALL || optimize_function_for_size_p (cfun))
+   /* FIXME: without this LRA can't reload this pattern, see PR82524.  */
+   && (rtx_equal_p (operands[0], operands[1])
+       || rtx_equal_p (operands[0], operands[2]))"
+  "<logic>{b}\t{%h2, %h0|%h0, %h2}"
+  [(set_attr "type" "alu")
+   (set_attr "mode" "QI")])
+
 ;; Convert wide OR instructions with immediate operand to shorter QImode
 ;; equivalents when possible.
 ;; Don't do the splitting with memory operands, since it introduces risk