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* config/h8300/h8300.md: Add comments about peephole2's. 

From-SVN: r78921
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Kazu Hirata 2004-03-04 18:05:06 +00:00 committed by Kazu Hirata
parent eb3d7f9d1f
commit d3c4083799
2 changed files with 68 additions and 9 deletions
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4
gcc/ChangeLog
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@ -1,3 +1,7 @@
2004-03-04 Kazu Hirata <kazu@cs.umass.edu>
* config/h8300/h8300.md: Add comments about peephole2's.
2004-03-04 Steven Bosscher <stevenb@suse.de>
* i386.h (TARGET_CPU_DEFAULT_nocona): Fix value.

73
gcc/config/h8300/h8300.md
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@ -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")