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lib1funcs.asm (DenHighNonZero): Optimize using the approximate quotient method.

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* config/h8300/lib1funcs.asm (DenHighNonZero): Optimize using
	the approximate quotient method.

Co-Authored-By: Kazu Hirata <kazu@cs.umass.edu>

From-SVN: r73550
This commit is contained in:
Pavel Pisa 2003-11-13 18:10:23 +01:00 committed by Kazu Hirata
parent 79ae853c64
commit 148a82c8ad
2 changed files with 56 additions and 25 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2003-11-13 Pavel Pisa <pisa@cmp.felk.cvut.cz>
Kazu Hirata <kazu@cs.umass.edu>
* config/h8300/lib1funcs.asm (DenHighNonZero): Optimize using
the approximate quotient method.
2003-11-13 Richard Earnshaw <rearnsha@arm.com>
* combine.c (distribute_notes): When re-distributing the notes from

75
gcc/config/h8300/lib1funcs.asm
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@ -603,32 +603,57 @@ divmodsi4:
extu.l S0P
rts
; er0 = er0 / er1
; er4 = er0 % er1
; trashes er1 er2
; expects er1 >= 2^16
DenHighNonZero:
sub.l S0P,S0P ; zero play area
mov.w A0E,A2
mov.b A2H,S0L
mov.b A2L,A2H
mov.b A0H,A2L
mov.w A2,A0E
mov.b A0L,A0H
mov.b #0,A0L
mov.b #24,S2H ; only do 24 iterations
nextbit:
shll.l A0P ; double the answer guess
rotxl.l S0P ; double remainder
sub.l A1P,S0P ; does it all fit?
bhs setone
add.l A1P,S0P ; no, restore mistake
dec S2H
bne nextbit
rts
setone:
inc A0L
dec S2H
bne nextbit
mov.l er0,er4
mov.l er1,er2
#ifdef __H8300H__
divmod_L21:
shlr.l er0
shlr.l er2 ; make divisor < 2^16
mov.w e2,e2
bne divmod_L21
#else
bra divmod_L22
divmod_L21:
shlr.l #2,er0
divmod_L22:
shlr.l #2,er2 ; make divisor < 2^16
mov.w e2,e2
bne divmod_L21
rotxl.w r2
bcs divmod_L23
shlr.l er0
bra divmod_L24
divmod_L23:
rotxr.w r2
shlr.l #2,er0
divmod_L24:
#endif
;; At this point,
;; er0 contains shifted dividend
;; er1 contains divisor
;; er2 contains shifted divisor
;; er4 contains dividend, later remainder
divxu.w r2,er0 ; e0 now contains the approximate quotient (AQ)
extu.l er0
beq divmod_L25
subs #1,er0 ; er0 = AQ - 1
mov.w e1,r2
mulxu.w r0,er2 ; er2 = upper (AQ - 1) * divisor
sub.w r2,e4 ; dividend - 65536 * er2
mov.w r1,r2
mulxu.w r0,er2 ; compute er4 = remainder (tentative)
sub.l er2,er4 ; er4 = dividend - (AQ - 1) * divisor
divmod_L25:
cmp.l er1,er4 ; is divisor < remainder?
blo divmod_L26
adds #1,er0
sub.l er1,er4 ; correct the remainder
divmod_L26:
rts
#endif