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runer112/roundf.src

Last active March 26, 2022 04:22
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EZ80 implementation of roundf
Raw
roundf.src
assume adl=1
section .text
public _roundf
_roundf:
; exponent_biased >= 0 && exponent_biased < 256
; && exponent_biased = exponent + 127
; = exponent + 127 >= 0 && exponent + 127 < 256
; = exponent >= -127 && exponent < 129
ld hl, 6
add hl, sp ; uhl = (char*)&arg + 3
ld e, (hl)
dec hl
ld d, (hl) ; d = exponent + 127 << 7 | fraction >> 16
dec hl
dec hl
ld hl, (hl) ; euhl = arg
ld a, e ; a = sign << 7 | exponent + 127 >> 1
inc a ; a = (sign << 7 | exponent + 127 >> 1) + 1
; = (sign << 7) + (exponent + 127 >> 1) + 1
; = (sign << 7) + (exponent + 129 >> 1)
add a, a ; a = (sign << 7) + (exponent + 129 >> 1) << 1
; = (sign << 8) + (exponent + 129 & ~1)
; = exponent + 129 & ~1
; sf = (exponent + 129 & ~1 & 0x80) != 0
; = (exponent + 129 & 0x80) != 0
; = (exponent + 1 + 0x80 & 0x80) != 0
; = (exponent + 1 & 0x80 ^ 0x80) != 0
; = (exponent + 1 & 0x80) != 0x80
; = (exponent + 1 & 0x80) == 0
; && exponent >= -127 && exponent < 129
; = exponent >= -1 && exponent < 127
; zf = (exponent + 129 & ~1) == 0
; && exponent >= -127 && exponent < 129
; = exponent == 127 || exponent = 128
; cf = ((sign << 7) + (exponent + 129 >> 1) & 0xFF) << 1 >> 8 != 0
; = ((sign << 7) + (exponent + 129 >> 1) & 0xFF) >> 7 != 0
; = ((sign << 7) + (exponent + 129 >> 1) >> 7 & 1) != 0
; = (sign + (exponent + 129 >> 8) & 1) != 0
; = (sign & 1) != 0 ^ (exponent + 129 >> 8 & 1) != 0
; && (sign == 0 || sign == 1)
; && exponent >= -127 && exponent < 129
; = sign != 0 ^ (exponent == 127 || exponent == 128)
jp p, .special
; exponent >= -1 && exponent < 127
sub a, 129 + 23 ; a = (exponent + 129 & ~1) - 129 - 23
; = exponent - 23 & ~1
; cf = (exponent - 23 & ~1 & 0x100) != 0
; = (exponent - 23 & 0x100) != 0
; && exponent >= -1 && exponent < 127
; = exponent < 23
ret nc
; exponent >= 1 && exponent < 23
rrca ; a = (exponent - 23 & ~1) << 7 | (exponent - 23 & ~1) >> 1
; = (exponent - 23 & ~1) << 7 | exponent - 23 >> 1
rrca ; a = (exponent - 23 & ~1) << 6 | exponent - 23 >> 2
; cf = ((exponent - 23 & ~1) << 7 | exponent - 23 >> 1) & 1 != 0
; = ((exponent - 23 & ~1) << 7 & 1 | exponent - 23 >> 1 & 1) != 0
; = (exponent - 23 >> 1 & 1) != 0
; = (exponent - 23 & 1 << 1) != 0
jr nc, .shift_bit_1_unset
rrca ; a = (exponent - 23 & ~1) << 5 | exponent - 23 >> 3
; cf = ((exponent - 23 & ~1) << 6 | exponent - 23 >> 2) & 1 != 0
; = ((exponent - 23 & ~1) << 6 & 1 | exponent - 23 >> 2 & 1) != 0
; = (exponent - 23 >> 2 & 1) != 0
; = (exponent - 23 & 1 << 2) != 0
ld bc, 1 shl (8 + 8 - 1 - 2)
jr nc, .shift_bits_2_1_done
ld b, 1 shl (8 - 1 - 2 - 4)
jr .shift_bits_2_1_done
.shift_bit_1_unset:
rrca ; a = (exponent - 23 & ~1) << 5 | exponent - 23 >> 3
; cf = ((exponent - 23 & ~1) << 6 | exponent - 23 >> 2) & 1 != 0
; = ((exponent - 23 & ~1) << 6 & 1 | exponent - 23 >> 2 & 1) != 0
; = (exponent - 23 >> 2 & 1) != 0
; = (exponent - 23 & 1 << 2) != 0
ld bc, 1 shl (8 + 8 - 1)
jr nc, .shift_bits_2_1_done
ld b, 1 shl (8 - 1 - 4)
.shift_bits_2_1_done: ; ubc = 1 << 8 + 8 - 1 - 2 * ((exponent - 23 & 1 << 1) != 0) - 4 * ((exponent - 23 & 1 << 2) != 0)
; = 1 << 15 - (exponent - 23 & 1 << 1) - (exponent - 23 & 1 << 2)
; = 1 << 15 - (exponent - 23 & (1 << 2 | 1 << 1))
bit 7, d ; zf = (exponent + 127 & 1) == 0
; = (exponent - 23 & 1) == 0
jr z, .shift_done
rrc b
.shift_done: ; ubc = 1 << 15 - (exponent - 23 & (1 << 2 | 1 << 1)) >> !((exponent - 23 & 1) == 0)
; = 1 << 15 - (exponent - 23 & (1 << 2 | 1 << 1)) >> (exponent - 23 & 1)
; = 1 << 15 - (exponent - 23 & (1 << 2 | 1 << 1)) - (exponent - 23 & 1)
; = 1 << 15 - (exponent - 23 & (1 << 2 | 1 << 1 | 1))
; = 1 << 15 - (exponent - 23 & 7)
rrca ; a = (exponent - 23 & ~1) << 4 | exponent - 23 >> 4
; cf = ((exponent - 23 & ~1) << 5 | exponent - 23 >> 3) & 1 != 0
; = ((exponent - 23 & ~1) << 5 & 1 | exponent - 23 >> 3 & 1) != 0
; = (exponent - 23 >> 3 & 1) != 0
; = (exponent - 23 & 1 << 3) != 0
; && exponent >= 1 && exponent < 23
; = (exponent >= -1 && exponent < 7) || (exponent >= 15 && exponent < 23)
jr nc, .round_2_bytes
; (exponent >= -1 && exponent < 7) || (exponent >= 15 && exponent < 23)
rrca ; a = (exponent - 23 & ~1) << 3 | exponent - 23 >> 5
; cf = ((exponent - 23 & ~1) << 4 | exponent - 23 >> 4) & 1 != 0
; = ((exponent - 23 & ~1) << 4 & 1 | exponent - 23 >> 4 & 1) != 0
; = (exponent - 23 >> 4 & 1) != 0
; = (exponent - 23 & 1 << 4) != 0
; && (exponent >= -1 && exponent < 7) || (exponent >= 15 && exponent < 23)
; = exponent >= 15 && exponent < 23
jr c, .round_1_byte
.round_3_bytes:
; exponent >= -1 && exponent < 7
; b = 1 << 7 - (exponent - 23 & 7)
; && exponent >= -1 && exponent < 7
; = 1 << 7 - (exponent + 1)
; = 1 << 6 - exponent
ld a, d ; ea = arg >> 16
add a, b
jr nc, .round_3_bytes_add_done
inc e
.round_3_bytes_add_done:
ld h, a ; eh = (arg >> 16) + (1 << 6 - exponent)
xor a, a
sub a, b ; a = -(1 << 6 - exponent)
; = -1 << 6 - exponent
add a, a ; a = -1 << 6 - exponent << 1
; = -1 << 7 - exponent
or a, 1 shl 7 ; a = -1 << 7 - exponent | 1 << 7
; && exponent >= -1 && exponent < 7
; = exponent == -1 ? -1 << 8 | 1 << 7 : -1 << 7 - exponent | 1 << 7
; = exponent == -1 ? -1 << 7 : -1 << 7 - exponent
; = -1 << 7 - (exponent == -1) - exponent
and a, h ; a = (arg >> 16) + (1 << 6 - exponent) & -1 << 7 - (exponent == -1) - exponent
push af
dec sp
pop hl ; e[hlu] = (arg >> 16) + (1 << 6 - exponent) & -1 << 7 - (exponent == -1) - exponent
inc sp
ld h, c
ld l, c ; euhl = arg + (1 << 22 - exponent) & -1 << 23 - (exponent == -1) - exponent
ret
.round_2_bytes:
; exponent >= 7 && exponent < 15
; b = 1 << 7 - (exponent - 23 & 7)
; && exponent >= 7 && exponent < 15
; = 1 << 7 - (exponent - 7)
; = 1 << 14 - exponent
; ubc = 1 << 22 - exponent
xor a, a
add hl, bc
adc a, e
ld e, a ; euhl = arg + (1 << 22 - exponent)
xor a, a
sub a, b ; a = -(1 << 14 - exponent)
; = -1 << 14 - exponent
add a, a ; a = -1 << 14 - exponent << 1
; = -1 << 15 - exponent
and a, h ; a = arg >> 8 & -1 << 15 - exponent
ld h, a
ld l, c ; euhl = arg + (1 << 22 - exponent) & -1 << 23 - exponent
ret
.round_1_byte:
; exponent >= 15 && exponent < 23
; b = 1 << 7 - (exponent - 23 & 7)
; && exponent >= 15 && exponent < 23
; = 1 << 7 - (exponent - 15)
; = 1 << 22 - exponent
xor a, a
ld c, b
ld b, a ; ubc = 1 << 22 - exponent
add hl, bc
adc a, e
ld e, a ; euhl = arg + (1 << 22 - exponent)
xor a, a
sub a, c ; a = -(1 << 22 - exponent)
; = -1 << 22 - exponent
add a, a ; a = -1 << 22 - exponent << 1
; = -1 << 23 - exponent
and a, l ; a = arg & -1 << 23 - exponent
ld l, a ; euhl = arg + (1 << 22 - exponent) & -1 << 23 - exponent
ret
.special:
; (exponent >= -127 && exponent < -1) || exponent == 127 || exponent = 128
; zf = exponent == 127 || exponent = 128
ret z
; exponent >= -127 && exponent < -1
; cf = sign
ld e, 0
rr e
sbc hl, hl ; euhl = sign << 31
ret
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