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Update add_align_exponents

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Rikard Nordgren authored and FeralChild64 committed 2026-03-29 21:45:24 +02:00
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commit 3c483446be
5 files changed
+23 -178
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STATUS.md
+1 -1
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@@ -207,7 +207,7 @@ Floating point mathematical routines - not official, but well known and broadly
| `$B849` | `add_HALF_FAC1` | DONE | From the Microsoft BASIC, original name: FADDH |
| `$B850` | `sub_MEM_FAC1` | DONE | From the Microsoft BASIC, original name: FSUB |
| `$B853` | `sub_FAC2_FAC1` | DONE | From the Microsoft BASIC, original name: FSUBT |
| `$B862` | `add_align_exponents` | DONE | |
| `$B862` | `add_align_exponents` | DONE | From the Microsoft BASIC, original name: FADD5 |
| `$B867` | `add_MEM_FAC1` | DONE | |
| `$B86A` | `add_FAC2_FAC1` | DONE | |
| `$B8D2` | `abs_and_normal_FAC` | DONE | From the Microsoft BASIC, original name: FADFLT |
src/basic/math/add_align_exponents.s
-167
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@@ -1,167 +0,0 @@
;; #LAYOUT# STD * #TAKE
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
;
; Math package - align FAC1 and FAC2 exponents for addition
;
; See also:
; - [CM64] Computes Mapping the Commodore 64 - page 115
; - https://www.c64-wiki.com/wiki/BASIC-ROM
add_align_exponents:
; XXX assume here none of the exponents is 0, check if this is true for orignal ROMs
lda FAC1_exponent
cmp FAC2_exponent
beq add_align_exponents_done ; branch if exponents the same
bcs add_align_exponent_FAC2
; FALLTROUGH
add_align_exponent_FAC1:
; First check the exponent difference
lda FAC2_exponent
sec
sbc FAC1_exponent
cmp #$28
bcs add_align_exponent_FAC1_zero ; branch if difference is very high
cmp #$08
bcc add_align_exponent_FAC1_bit
; FALLTROUGH
add_align_exponent_FAC1_byte:
; Add 8 to exponent, divide mantissa by 256
lda FAC1_exponent
clc
adc #$08
sta FAC1_exponent
lda FAC1_mantissa+3
sta FACOV
lda FAC1_mantissa+2
sta FAC1_mantissa+3
lda FAC1_mantissa+1
sta FAC1_mantissa+2
lda FAC1_mantissa+0
sta FAC1_mantissa+1
lda #$00
sta FAC1_mantissa+0
beq add_align_exponent_FAC1 ; branch always - next iteration
add_align_exponent_FAC1_bit:
; Increment exponent, divide mantissa by 2
inc FAC1_exponent
clc
ror FAC1_mantissa+0
ror FAC1_mantissa+1
ror FAC1_mantissa+2
ror FAC1_mantissa+3
ror FACOV
lda FAC1_exponent
cmp FAC2_exponent
bne add_align_exponent_FAC1_bit ; branch if next iteration needed
rts
add_align_exponent_FAC1_zero:
lda #$00
sta FAC1_mantissa+0
sta FAC1_mantissa+1
sta FAC1_mantissa+2
sta FAC1_mantissa+3
sta FACOV
lda FAC2_exponent
sta FAC1_exponent
; FALLTROUGH
add_align_exponents_done:
rts
add_align_exponent_FAC2:
; First check the exponent difference, Carry already set here
lda FAC1_exponent
sbc FAC2_exponent
cmp #$20
bcs add_align_exponent_FAC2_zero ; branch if difference is very high
cmp #$08
bcc add_align_exponent_FAC2_bit
; FALLTROUGH
add_align_exponent_FAC2_byte:
; Add 8 to exponent, divide mantissa by 256
lda FAC2_exponent
clc
adc #$08
sta FAC2_exponent
lda FAC2_mantissa+2
sta FAC2_mantissa+3
lda FAC2_mantissa+1
sta FAC2_mantissa+2
lda FAC2_mantissa+0
sta FAC2_mantissa+1
lda #$00
sta FAC2_mantissa+0
beq add_align_exponent_FAC2 ; branch always - next iteration
add_align_exponent_FAC2_bit:
; Increment exponent, divide mantissa by 2
inc FAC2_exponent
clc
ror FAC2_mantissa+0
ror FAC2_mantissa+1
ror FAC2_mantissa+2
ror FAC2_mantissa+3
lda FAC1_exponent
cmp FAC2_exponent
bne add_align_exponent_FAC2_bit ; branch if next iteration needed
rts
add_align_exponent_FAC2_zero:
lda #$00
sta FAC2_mantissa+0
sta FAC2_mantissa+1
sta FAC2_mantissa+2
sta FAC2_mantissa+3
lda FAC1_exponent
sta FAC2_exponent
rts
src/basic/math/b862.add_align_exponent.jmp.s
-9
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@@ -1,9 +0,0 @@
;; #LAYOUT# STD * #TAKE
;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
; Just a compatibility jump - our routine is longer than original one
jmp add_align_exponents
src/basic/math/b862.add_align_exponent.s
+21
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@@ -0,0 +1,21 @@
;; #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 - align FAC1 and FAC2 exponents for addition
;
; This is verified to be identical to the original Microsoft implementation where it was named FADD5.
;
; See also:
; - [CM64] Computes Mapping the Commodore 64 - page 115
; - https://www.c64-wiki.com/wiki/BASIC-ROM
add_align_exponents:
jsr shiftr_FAC
bcc FADD4
; Fallthrough to add_MEM_FAC1
tools/similarity.c
+1 -1
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@@ -25,7 +25,7 @@ int phase_mask[MAX_SIZE+MAX_SIZE];
unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {
0xB391, 0xB39D,
0xB3A2, 0xB3A5,
0xB849, 0xB861,
0xB849, 0xB866,
0xB8D2, 0xB8D5,
0xB947, 0xB97D,
0xB983, 0xB9BB,