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[patch] h8300.md: Add comments about peephole2's.
- From: Kazu Hirata <kazu at cs dot umass dot edu>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 04 Mar 2004 13:05:14 -0500 (EST)
- Subject: [patch] h8300.md: Add comments about peephole2's.
Hi,
Attached is a patch to add comments about peephole2's.
Committed.
Kazu Hirata
2004-03-04 Kazu Hirata <kazu@cs.umass.edu>
* config/h8300/h8300.md: Add comments about peephole2's.
Index: h8300.md
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/h8300/h8300.md,v
retrieving revision 1.282
diff -u -r1.282 h8300.md
--- h8300.md 2 Mar 2004 06:05:59 -0000 1.282
+++ h8300.md 4 Mar 2004 17:59:55 -0000
@@ -4373,8 +4373,15 @@
;;
;; ---- 65535 geu/ltu mov.w
-;; For a small constant, it is cheaper to actually do the subtraction
-;; and then test the register.
+;; Transform
+;;
+;; cmp.l #1,er0
+;; beq .L1
+;;
+;; into
+;;
+;; dec.l #1,er0
+;; beq .L1
(define_peephole2
[(set (cc0)
@@ -4399,6 +4406,16 @@
(pc)))]
"operands[4] = GEN_INT (- INTVAL (operands[1]));")
+;; Transform
+;;
+;; cmp.l #65536,er0
+;; beq .L1
+;;
+;; into
+;;
+;; dec.l #1,e0
+;; beq .L1
+
(define_peephole2
[(set (cc0)
(compare (match_operand:SI 0 "register_operand" "")
@@ -4425,9 +4442,16 @@
(pc)))]
"operands[4] = GEN_INT (- INTVAL (operands[1]));")
-;; For certain (in)equality comparisons against a constant, we can
-;; XOR the register with the constant, and test the register against
-;; 0.
+;; Transform
+;;
+;; cmp.l #100,er0
+;; beq .L1
+;;
+;; into
+;;
+;; xor.b #100,er0
+;; mov.l er0,er0
+;; beq .L1
(define_peephole2
[(set (cc0)
@@ -4456,6 +4480,17 @@
(pc)))]
"")
+;; Transform
+;;
+;; cmp.l #-100,er0
+;; beq .L1
+;;
+;; into
+;;
+;; xor.b #99,er0
+;; not.l er0
+;; beq .L1
+
(define_peephole2
[(set (cc0)
(compare (match_operand:SI 0 "register_operand" "")
@@ -4484,6 +4519,17 @@
(pc)))]
"operands[4] = GEN_INT (INTVAL (operands[1]) ^ -1);")
+;; Transform
+;;
+;; cmp.l #-2147483648,er0
+;; beq .L1
+;;
+;; into
+;;
+;; rotl.l er0
+;; dec.l #1,er0
+;; beq .L1
+
(define_peephole2
[(set (cc0)
(compare (match_operand:SI 0 "register_operand" "")
@@ -4829,10 +4875,19 @@
const0_rtx);
})
-;; For constants like -1, -2, 1, 2, it is still cheaper to make a copy
-;; of the register being tested, do the subtraction on the copy, and
-;; then test the copy. We avoid this transformation if we see more
-;; than one copy of the same compare insn.
+;; Transform
+;;
+;; cmp.l #1,er0
+;; beq .L1
+;;
+;; into
+;;
+;; mov.l er0,er1
+;; dec.l #1,er1
+;; beq .L1
+
+;; We avoid this transformation if we see more than one copy of the
+;; same compare insn.
(define_peephole2
[(match_scratch:SI 4 "r")