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Update mul_FAC2_FAC1

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Rikard Nordgren authored and FeralChild64 committed 2026-04-12 13:13:18 +02:00
1 parent 908b783319
commit 582ecedbd1
7 files changed
+123 -249
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STATUS.md
+1 -1
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@@ -220,7 +220,7 @@ Floating point mathematical routines - not official, but well known and broadly
| `$B983` | `shiftr_FAC1` | DONE | From the Microsoft BASIC, original name: SHIFTR |
| `$B9EA` | `log_FAC1` | PARTIAL | not fully tested yet |
| `$BA28` | `mul_MEM_FAC1` | DONE | From the Microsoft BASIC, original name: FMULT |
| `$BA2B` | `mul_FAC2_FAC1` | DONE | |
| `$BA2B` | `mul_FAC2_FAC1` | DONE | From the Microsoft BASIC, original name: FMULTT |
| `$BA8C` | `mov_MEM_FAC2` | DONE | From the Microsoft BASIC, original name: CONUPK |
| `$BA90` | `get_FAC2_via_INDEX` | DONE | From the Microsoft BASIC, no label |
| `$BAE2` | `mul10_FAC1` | DONE | |
src/basic/math/ba2b.mul_FAC2_FAC1.s
+71 -2
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@@ -3,6 +3,75 @@
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
; Just a compatibility jump - our routine is longer than original one
; This file is under the MIT license, it contains code released by Microsoft Corporation.
; See LICENSE for more information.
jmp mul_FAC2_FAC1
; Math package - multiplies FAC1 by FAC2
;
; This is verified to be identical to the original Microsoft implementation where it was named FMULTT
;
; Input:
; - .A - must load FAC1 exponent ($61) beforehand to set the zero flag
;
;
; See also:
; - [CM64] Computes Mapping the Commodore 64 - page 113 XXX address does not match
; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
;
mul_FAC2_FAC1:
bne @1
jmp MULTRT ; If FAC1=0 return. FAC1 is set
@1: jsr MULDIV ; Fix up the exponents
lda #0 ; To clear result
sta RESHO+0
sta RESHO+1
sta RESHO+2
sta RESHO+3
lda FACOV
jsr MLTPLY
lda FAC1_mantissa+3
jsr MLTPLY
lda FAC1_mantissa+2
jsr MLTPLY
lda FAC1_mantissa+1
jsr MLTPLY
lda FAC1_mantissa+0
jsr MLTPL1
jmp mov_RES_FAC1 ; Move result into FAC1, normalize and return
MLTPLY:
bne MLTPL1
jmp shift_for_mul_RES ; Shift result right 1 byte
MLTPL1:
lsr
ora #$80
MLTPL2:
tay
bcc MLTPL3 ; If mult bit=0, just shift
clc
lda RESHO+3
adc FAC2_mantissa+3
sta RESHO+3
lda RESHO+2
adc FAC2_mantissa+2
sta RESHO+2
lda RESHO+1
adc FAC2_mantissa+1
sta RESHO+1
lda RESHO+0
adc FAC2_mantissa+0
sta RESHO+0
MLTPL3:
ror RESHO+0
ror RESHO+1
ror RESHO+2
ror RESHO+3
ror FACOV ; Save for rounding
tya
lsr ; Clear MSB so we get closer to 0
bne MLTPL2 ; Slow as a turtle!
MULTRT:
rts
src/basic/math/bab7.MULDIV.s
+47
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@@ -0,0 +1,47 @@
;; #LAYOUT# STD * #TAKE
;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
; This file is under the MIT license, it contains code released by Microsoft Corporation.
; See LICENSE for more information.
; Math package - add exponents of FAC1 and FAC2 for multiplication and division
;
; This is verified to be identical to the original Microsoft implementation where it was named MULDIV
;
;CHECK SPECIAL CASES AND ADD EXPONENTS FOR FMULT, FDIV.
MULDIV:
lda FAC2_exponent ; Exponent of FAC2 = 0?
MLDEXP:
beq ZEREMV
clc
adc FAC1_exponent ; Result is in A
bcc @1 ; Find CF XOR NF
bmi GOOVER ; Overflow if bits match
clc
+skip_2_bytes_trash_nvz
@1:
bpl ZEREMV ; underflow
adc #$80 ; Add bias
sta FAC1_exponent
bne @2
jmp ZEROML ; Zero the rest of it
@2:
lda ARISGN
sta FAC1_sign ; ARISGN is result's sign
rts
MLDVEX:
lda FAC1_sign
eor #$FF
bmi GOOVER
ZEREMV:
pla ; Get address off stack
pla
jmp zero_FAC1 ; underflow
GOOVER:
jmp overflow_error ; overflow
src/basic/math/bb12.div_FAC2_FAC1.s
+2 -2
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@@ -32,7 +32,7 @@ div_FAC2_FAC1:
; Handle special case - dividing 0 by non-zero value
lda FAC2_exponent
+beq set_FAC1_zero
+beq clear_FAC1
; Multiply signs
@@ -59,7 +59,7 @@ div_FAC2_FAC1:
@1:
lda RESHO+1
+bmi set_FAC1_zero ; result too low, set 0 and quit
+bmi clear_FAC1 ; result too low, set 0 and quit
lda RESHO+0
sta FAC1_exponent
src/basic/math/mul_FAC2_FAC1.s
-195
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@@ -1,195 +0,0 @@
;; #LAYOUT# STD * #TAKE
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
;
; Math package - multiplies FAC1 by FAC2
;
; Input:
; - .A - must load FAC1 exponent ($61) beforehand to set the zero flag
;
; Note:
; - load FAC2 after FAC1, or mimic the Kernals sign comparison (XXX do we need it?)
;
; See also:
; - [CM64] Computes Mapping the Commodore 64 - page 113 XXX address does not match
; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
;
set_FAC1_zero:
lda #$00
sta FAC1_exponent
mul_FAC2_FAC1_done:
rts
mul_FAC2_FAC1:
; First handle special case of multiplying by 0
lda FAC1_exponent
beq mul_FAC2_FAC1_done
lda FAC2_exponent
bne @1
sta FAC1_exponent
beq mul_FAC2_FAC1_done
@1:
; Multiply signs
lda FAC1_sign
eor FAC2_sign
sta FAC1_sign
; Add the exponents (subtract the bias) - XXX can this be optimized somehow?
jsr muldiv_RESHO_set_0
lda FAC1_exponent
jsr muldiv_RESHO_01_add_A
lda FAC2_exponent
jsr muldiv_RESHO_01_add_A
lda RESHO+0
sbc #$80 ; we need to correct double BIAS
sta RESHO+0
bcs @2
lda RESHO+1
sbc #$00
bcc set_FAC1_zero
sta RESHO+1
@2:
lda RESHO+1
+bne overflow_error ; overflow
lda RESHO+0
sta FAC1_exponent
; Multiply the mantissas
jsr muldiv_RESHO_set_0
clc
; XXX maybe we should preserve .X on stack? this will not cost us too much
lda FACOV
jsr mul_FAC2_FAC1_by_A
jsr mul_FAC2_FAC1_shift
bcc @3
inc RESHO+0
@3:
lda FAC1_mantissa+3
jsr mul_FAC2_FAC1_by_A
jsr mul_FAC2_FAC1_shift
bcc @4
inc RESHO+0
@4:
lda FAC1_mantissa+2
jsr mul_FAC2_FAC1_by_A
jsr mul_FAC2_FAC1_shift
bcc @5
inc RESHO+0
@5:
lda FAC1_mantissa+1
jsr mul_FAC2_FAC1_by_A
jsr mul_FAC2_FAC1_shift
bcc @6
inc RESHO+0
@6:
lda FAC1_mantissa+0
jsr mul_FAC2_FAC1_by_A
jsr mul_FAC2_FAC1_shift
bcc @7
inc RESHO+0
@7:
; Copy RESHO to FAC1 mantissa
lda RESHO+4
sta FACOV
lda RESHO+3
sta FAC1_mantissa+3
lda RESHO+2
sta FAC1_mantissa+2
lda RESHO+1
sta FAC1_mantissa+1
lda RESHO+0
sta FAC1_mantissa+0
; Correct the exponent
lda FAC1_exponent
clc
adc #$08
+bcs overflow_error ; branch if overflow
sta FAC1_exponent
jmp normal_FAC1
mul_FAC2_FAC1_by_A:
beq mul_FAC2_FAC1_by_A_done
sta INDEX+3
; Multiply FAC2_mantissa+3
lda FAC2_mantissa+3
jsr mul_FAC2_FAC1_8x8
adc RESHO+4
sta RESHO+4
txa
adc RESHO+3
sta RESHO+3
bcc @8
inc RESHO+2
bne @8
inc RESHO+1
bne @8
inc RESHO+0
@8:
; Multiply FAC2_mantissa+2
lda FAC2_mantissa+2
jsr mul_FAC2_FAC1_8x8
adc RESHO+3
sta RESHO+3
txa
adc RESHO+2
sta RESHO+2
bcc @9
inc RESHO+1
bne @9
inc RESHO+0
@9:
; Multiply FAC2_mantissa+1
lda FAC2_mantissa+1
jsr mul_FAC2_FAC1_8x8
adc RESHO+2
sta RESHO+2
txa
adc RESHO+1
sta RESHO+1
bcc @10
inc RESHO+0
@10:
; Multiply FAC2_mantissa+0
lda FAC2_mantissa+0
jsr mul_FAC2_FAC1_8x8
adc RESHO+1
sta RESHO+1
txa
adc RESHO+0
sta RESHO+0
; FALLTROUGH
mul_FAC2_FAC1_by_A_done:
rts
src/basic/math/mul_FAC2_FAC1_shift.s
-46
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@@ -1,46 +0,0 @@
;; #LAYOUT# STD * #TAKE
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
;
; Shift RESHO by one byte - for multiplication
;
mul_FAC2_FAC1_shift:
; Check if rounding is needed
php
clc
lda RESHO+4
bpl @1
sec
@1:
; Copy bytes
lda RESHO+3
sta RESHO+4
lda RESHO+2
sta RESHO+3
lda RESHO+1
sta RESHO+2
lda RESHO+0
sta RESHO+1
lda #$00
sta RESHO+0
bcc @2
; Perform rounding
inc RESHO+4
bne @2
inc RESHO+3
bne @2
inc RESHO+2
bne @2
inc RESHO+1
bne @2
inc RESHO+0
@2:
plp
rts
tools/similarity.c
+2 -3
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@@ -20,15 +20,14 @@ int matches[MAX_SIZE];
int phase_mask[MAX_SIZE+MAX_SIZE];
#define NUM_CHUNKS 7
#define NUM_CHUNKS 6
// Pairs of start, end memory addresses of known exact similarity with the open source Microsoft BASIC
unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {
0xB391, 0xB39D,
0xB3A2, 0xB3A5,
0xB849, 0xB97D,
0xB983, 0xB9BB,
0xBA28, 0xBA2A,
0xBA8C, 0xBAB6,
0xBA28, 0xBAE1,
0xBB8F, 0xBCF2,
};