mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-14 01:00:07 +00:00
274 lines
6.5 KiB
ArmAsm
274 lines
6.5 KiB
ArmAsm
/* Copyright (C) 2004-2020 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library. If not, see
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include "div_libc.h"
|
|
|
|
|
|
/* 64-bit signed long divide. These are not normal C functions. Argument
|
|
registers are t10 and t11, the result goes in t12. Only t12 and AT may
|
|
be clobbered.
|
|
|
|
Theory of operation here is that we can use the FPU divider for virtually
|
|
all operands that we see: all dividend values between -2**53 and 2**53-1
|
|
can be computed directly. Note that divisor values need not be checked
|
|
against that range because the rounded fp value will be close enough such
|
|
that the quotient is < 1, which will properly be truncated to zero when we
|
|
convert back to integer.
|
|
|
|
When the dividend is outside the range for which we can compute exact
|
|
results, we use the fp quotent as an estimate from which we begin refining
|
|
an exact integral value. This reduces the number of iterations in the
|
|
shift-and-subtract loop significantly.
|
|
|
|
The FPCR save/restore is due to the fact that the EV6 _will_ set FPCR_INE
|
|
for cvttq/c even without /sui being set. It will not, however, properly
|
|
raise the exception, so we don't have to worry about FPCR_INED being clear
|
|
and so dying by SIGFPE. */
|
|
|
|
.text
|
|
.align 4
|
|
.globl __divq
|
|
.type __divq, @funcnoplt
|
|
.usepv __divq, no
|
|
|
|
cfi_startproc
|
|
cfi_return_column (RA)
|
|
__divq:
|
|
lda sp, -FRAME(sp)
|
|
cfi_def_cfa_offset (FRAME)
|
|
CALL_MCOUNT
|
|
|
|
/* Get the fp divide insn issued as quickly as possible. After
|
|
that's done, we have at least 22 cycles until its results are
|
|
ready -- all the time in the world to figure out how we're
|
|
going to use the results. */
|
|
stt $f0, 0(sp)
|
|
excb
|
|
beq Y, DIVBYZERO
|
|
|
|
stt $f1, 8(sp)
|
|
stt $f3, 48(sp)
|
|
cfi_rel_offset ($f0, 0)
|
|
cfi_rel_offset ($f1, 8)
|
|
cfi_rel_offset ($f3, 48)
|
|
mf_fpcr $f3
|
|
|
|
_ITOFT2 X, $f0, 16, Y, $f1, 24
|
|
cvtqt $f0, $f0
|
|
cvtqt $f1, $f1
|
|
divt/c $f0, $f1, $f0
|
|
|
|
/* Check to see if X fit in the double as an exact value. */
|
|
sll X, (64-53), AT
|
|
ldt $f1, 8(sp)
|
|
sra AT, (64-53), AT
|
|
cmpeq X, AT, AT
|
|
beq AT, $x_big
|
|
|
|
/* If we get here, we're expecting exact results from the division.
|
|
Do nothing else besides convert and clean up. */
|
|
cvttq/c $f0, $f0
|
|
excb
|
|
mt_fpcr $f3
|
|
_FTOIT $f0, RV, 16
|
|
|
|
ldt $f0, 0(sp)
|
|
ldt $f3, 48(sp)
|
|
cfi_restore ($f1)
|
|
cfi_remember_state
|
|
cfi_restore ($f0)
|
|
cfi_restore ($f3)
|
|
cfi_def_cfa_offset (0)
|
|
lda sp, FRAME(sp)
|
|
ret $31, (RA), 1
|
|
|
|
.align 4
|
|
cfi_restore_state
|
|
$x_big:
|
|
/* If we get here, X is large enough that we don't expect exact
|
|
results, and neither X nor Y got mis-translated for the fp
|
|
division. Our task is to take the fp result, figure out how
|
|
far it's off from the correct result and compute a fixup. */
|
|
stq t0, 16(sp)
|
|
stq t1, 24(sp)
|
|
stq t2, 32(sp)
|
|
stq t5, 40(sp)
|
|
cfi_rel_offset (t0, 16)
|
|
cfi_rel_offset (t1, 24)
|
|
cfi_rel_offset (t2, 32)
|
|
cfi_rel_offset (t5, 40)
|
|
|
|
#define Q RV /* quotient */
|
|
#define R t0 /* remainder */
|
|
#define SY t1 /* scaled Y */
|
|
#define S t2 /* scalar */
|
|
#define QY t3 /* Q*Y */
|
|
|
|
/* The fixup code below can only handle unsigned values. */
|
|
or X, Y, AT
|
|
mov $31, t5
|
|
blt AT, $fix_sign_in
|
|
$fix_sign_in_ret1:
|
|
cvttq/c $f0, $f0
|
|
|
|
_FTOIT $f0, Q, 8
|
|
.align 3
|
|
$fix_sign_in_ret2:
|
|
ldt $f0, 0(sp)
|
|
stq t3, 0(sp)
|
|
cfi_restore ($f0)
|
|
cfi_rel_offset (t3, 0)
|
|
|
|
mulq Q, Y, QY
|
|
excb
|
|
stq t4, 8(sp)
|
|
mt_fpcr $f3
|
|
cfi_rel_offset (t4, 8)
|
|
|
|
subq QY, X, R
|
|
mov Y, SY
|
|
mov 1, S
|
|
bgt R, $q_high
|
|
|
|
$q_high_ret:
|
|
subq X, QY, R
|
|
mov Y, SY
|
|
mov 1, S
|
|
bgt R, $q_low
|
|
|
|
$q_low_ret:
|
|
ldq t0, 16(sp)
|
|
ldq t1, 24(sp)
|
|
ldq t2, 32(sp)
|
|
bne t5, $fix_sign_out
|
|
|
|
$fix_sign_out_ret:
|
|
ldq t3, 0(sp)
|
|
ldq t4, 8(sp)
|
|
ldq t5, 40(sp)
|
|
ldt $f3, 48(sp)
|
|
lda sp, FRAME(sp)
|
|
cfi_remember_state
|
|
cfi_restore (t0)
|
|
cfi_restore (t1)
|
|
cfi_restore (t2)
|
|
cfi_restore (t3)
|
|
cfi_restore (t4)
|
|
cfi_restore (t5)
|
|
cfi_restore ($f3)
|
|
cfi_def_cfa_offset (0)
|
|
ret $31, (RA), 1
|
|
|
|
.align 4
|
|
cfi_restore_state
|
|
/* The quotient that we computed was too large. We need to reduce
|
|
it by S such that Y*S >= R. Obviously the closer we get to the
|
|
correct value the better, but overshooting high is ok, as we'll
|
|
fix that up later. */
|
|
0:
|
|
addq SY, SY, SY
|
|
addq S, S, S
|
|
$q_high:
|
|
cmpult SY, R, AT
|
|
bne AT, 0b
|
|
|
|
subq Q, S, Q
|
|
unop
|
|
subq QY, SY, QY
|
|
br $q_high_ret
|
|
|
|
.align 4
|
|
/* The quotient that we computed was too small. Divide Y by the
|
|
current remainder (R) and add that to the existing quotient (Q).
|
|
The expectation, of course, is that R is much smaller than X. */
|
|
/* Begin with a shift-up loop. Compute S such that Y*S >= R. We
|
|
already have a copy of Y in SY and the value 1 in S. */
|
|
0:
|
|
addq SY, SY, SY
|
|
addq S, S, S
|
|
$q_low:
|
|
cmpult SY, R, AT
|
|
bne AT, 0b
|
|
|
|
/* Shift-down and subtract loop. Each iteration compares our scaled
|
|
Y (SY) with the remainder (R); if SY <= R then X is divisible by
|
|
Y's scalar (S) so add it to the quotient (Q). */
|
|
2: addq Q, S, t3
|
|
srl S, 1, S
|
|
cmpule SY, R, AT
|
|
subq R, SY, t4
|
|
|
|
cmovne AT, t3, Q
|
|
cmovne AT, t4, R
|
|
srl SY, 1, SY
|
|
bne S, 2b
|
|
|
|
br $q_low_ret
|
|
|
|
.align 4
|
|
$fix_sign_in:
|
|
/* If we got here, then X|Y is negative. Need to adjust everything
|
|
such that we're doing unsigned division in the fixup loop. */
|
|
/* T5 records the changes we had to make:
|
|
bit 0: set if result should be negative.
|
|
bit 2: set if X was negated.
|
|
bit 3: set if Y was negated.
|
|
*/
|
|
xor X, Y, AT
|
|
cmplt AT, 0, t5
|
|
cmplt X, 0, AT
|
|
negq X, t0
|
|
|
|
s4addq AT, t5, t5
|
|
cmovne AT, t0, X
|
|
cmplt Y, 0, AT
|
|
negq Y, t0
|
|
|
|
s8addq AT, t5, t5
|
|
cmovne AT, t0, Y
|
|
unop
|
|
blbc t5, $fix_sign_in_ret1
|
|
|
|
cvttq/c $f0, $f0
|
|
_FTOIT $f0, Q, 8
|
|
.align 3
|
|
negq Q, Q
|
|
br $fix_sign_in_ret2
|
|
|
|
.align 4
|
|
$fix_sign_out:
|
|
/* Now we get to undo what we did above. */
|
|
/* ??? Is this really faster than just increasing the size of
|
|
the stack frame and storing X and Y in memory? */
|
|
and t5, 8, AT
|
|
negq Y, t4
|
|
cmovne AT, t4, Y
|
|
|
|
and t5, 4, AT
|
|
negq X, t4
|
|
cmovne AT, t4, X
|
|
|
|
negq RV, t4
|
|
cmovlbs t5, t4, RV
|
|
|
|
br $fix_sign_out_ret
|
|
|
|
cfi_endproc
|
|
.size __divq, .-__divq
|
|
|
|
DO_DIVBYZERO
|