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[patch] h8300.md: Add a new peephole2.


Hi,

Attached is a patch to add a new peephole2.  The new peephole2
transforms a reg-constant comparison in SImode like

	cmp.l	#23,er0 ; compare er0 against 23
 	beq	.L1     ; jump if equal

into

	xor.b	#23,r0l ; er0 ^= 23
	mov.l	er0,er0 ; test er0
 	beq	.L1     ; jump if equal

saving 2 bytes if er0 is dead, and the constants is of one of the
following forms

  0x000000??
  0x0000??00
  0x0000ffff
  0xffff0000

This peephole2 does not handle constants 1 and 2 because there are
faster ways for them.

Tested on h8300 port.  Committed.

Kazu Hirata

2003-02-13  Kazu Hirata  <kazu@cs.umass.edu>

	* config/h8300/h8300.md (a peephole2): New.

Index: h8300.md
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/h8300/h8300.md,v
retrieving revision 1.164
diff -u -r1.164 h8300.md
--- h8300.md	12 Feb 2003 23:32:21 -0000	1.164
+++ h8300.md	13 Feb 2003 13:05:30 -0000
@@ -3435,6 +3435,36 @@
 		      (pc)))]
   "")
 
+;; (compare:SI (reg) (const_int)) takes 6 bytes, so we try to achieve
+;; the equivalent with shorter sequences.  Here is the summary.
+;;
+;; reg  const_int                 use     insn
+;; live    -2                     eq/ne   copy and inc.l
+;; live    -1                     eq/ne   copy and inc.l
+;; live     1                     eq/ne   copy and dec.l
+;; live     2                     eq/ne   copy and dec.l
+;; dead    -6                     eq/ne   adds and inc.l
+;; dead    -5                     eq/ne   adds and inc.l
+;; dead    -4                     eq/ne   adds and test
+;; dead    -3                     eq/ne   adds and inc.l
+;; dead    -2                     eq/ne   inc.l
+;; dead    -1                     eq/ne   inc.l
+;; dead     1                     eq/ne   dec.l
+;; dead     2                     eq/ne   dec.l
+;; dead 0x000000?? except 1 and 2 eq/ne   xor.b and test
+;; dead 0x0000??00                eq/ne   xor.b and test
+;; dead 0x0000ffff                eq/ne   not.w and test
+;; dead 0xffff0000                eq/ne   not.w and test
+;; dead     1                     geu/ltu and.b and test
+;; dead     3                     geu/ltu and.b and test
+;; dead     7                     geu/ltu and.b and test
+;; dead    15                     geu/ltu and.b and test
+;; dead    31                     geu/ltu and.b and test
+;; dead    63                     geu/ltu and.b and test
+;; dead   127                     geu/ltu and.b and test
+;; dead   255                     geu/ltu and.b and test
+;; dead 65535                     geu/ltu mov.w
+
 ;; For a small constant, it is cheaper to actually do the subtraction
 ;; and then test the register.
 
@@ -3479,6 +3509,38 @@
 		      (pc)))]
   "operands[1] = GEN_INT (- INTVAL (operands[1]));
    split_adds_subs (SImode, operands, 1);")
+
+;; For certain (in)equaltity comparisions against a constant, we can
+;; XOR the register with the constant, and test the register against
+;; 0.
+
+(define_peephole2
+  [(set (cc0)
+	(compare:SI (match_operand:SI 0 "register_operand" "")
+		    (match_operand:SI 1 "const_int_operand" "")))
+   (set (pc)
+	(if_then_else (match_operator 3 "eqne_operator"
+			[(cc0) (const_int 0)])
+		      (label_ref (match_operand 2 "" ""))
+		      (pc)))]
+  "(TARGET_H8300H || TARGET_H8300S)
+   && peep2_reg_dead_p (1, operands[0])
+   && ((INTVAL (operands[1]) & 0x00ff) == INTVAL (operands[1])
+       || (INTVAL (operands[1]) & 0xff00) == INTVAL (operands[1])
+       || INTVAL (operands[1]) == 0x0000ffff
+       || INTVAL (operands[1]) == 0xffff0000)
+   && INTVAL (operands[1]) != 1
+   && INTVAL (operands[1]) != 2"
+  [(set (match_dup 0)
+	(xor:SI (match_dup 0)
+		(match_dup 1)))
+   (set (cc0)
+	(match_dup 0))
+   (set (pc)
+	(if_then_else (match_op_dup 3 [(cc0) (const_int 0)])
+		      (label_ref (match_dup 2))
+		      (pc)))]
+  "")
 
 ;; Transform A <= 1 to (A & 0xfffffffe) == 0.
 


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