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Add get_FAC1_via_INDEX

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Also change to only use bit 7 as sign in FAC1 and FAC2 (as the original BASIC does) to simplify
implementations.
This commit is contained in:
Rikard Nordgren committed 2025-04-01 19:42:21 +02:00
1 parent 919f3c84b9
commit 5a3f65efa4
18 files changed
+130 -134
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src/basic/,stubs_math/bba6.get_FAC1_via_INDEX.s
-17
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@@ -1,17 +0,0 @@
;; #LAYOUT# STD * #TAKE
;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
;
; Math package - XXX
;
; See also:
; - https://sourceforge.net/p/acme-crossass/code-0/38/tree/trunk/ACME_Lib/cbm/c64/float.a?force=True
;
; XXX implement, test
get_FAC1_via_INDEX:
+STUB_IMPLEMENTATION
src/basic/math/FCOMP.s
+12 -14
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@@ -32,11 +32,9 @@ FCOMP:
php
ldy #$01
lda #$7F ; Expand sign of RAM float into A as $FF or $00
cmp (INDEX+2),Y
adc #$80
cmp FAC1_sign
bne FCOMP_greater_than ; FAC < or > RAM, will be swapped to correct
lda (INDEX+2),Y
eor FAC1_sign ; Check if signs are different
bmi FCOMP_greater_than ; FAC < or > RAM, will be swapped to correct
dey
lda (INDEX+2),Y ; Exponent of RAM float into A
@@ -76,17 +74,17 @@ FCOMP_equal:
FCOMP_less_than:
lda #$FF
cmp FAC1_sign
bne @1
lda FAC1_sign
bpl FCOMP_FF
FCOMP_01:
lda #$01
@1: plp
plp
rts
FCOMP_greater_than:
lda #$01
cmp FAC1_sign
bcs @1
lda FAC1_sign
bpl FCOMP_01
FCOMP_FF:
lda #$FF
@1: plp
plp
rts
src/basic/math/bc2b.sgn_FAC1_A.s
+5 -1
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@@ -20,7 +20,11 @@ sgn_FAC1_A:
lda FAC1_exponent
beq @1
lda FAC1_sign
bne @1
bmi @2
lda #$01
@1:
rts
@2:
lda #$FF
rts
src/basic/math_mov/ba90.get_FAC2_via_INDEX.s
+1 -11
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@@ -33,20 +33,10 @@ get_FAC2_via_INDEX:
dey
lda (INDEX), y
sta FAC2_sign
ora #$80 ; clear the sign bit
sta FAC2_mantissa+0
; Copy the sign
lda (INDEX), y
bpl @1 ; assumption: non-negative numbers are more frequent
lda #$FF
+skip_2_bytes_trash_nvz
@1:
lda #$00
sta FAC2_sign
; Copy the exponent
dey
src/basic/math_mov/bba2.mov_MEM_FAC1.jmp.s
-8
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@@ -1,8 +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 mov_MEM_FAC1
src/basic/math_mov/bba2.mov_MEM_FAC1.s
+30
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@@ -0,0 +1,30 @@
;; #LAYOUT# STD * #TAKE
;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
; Math package - fetch FAC1 from RAM location
;
; Input:
; - .A - address low byte
; - .Y - address high byte
;
; Output:
; - .A - FAC1 exponent, affects status flags
; - .Y - always 0
;
; Preserves:
; - .X - (experimentation with original ROM)
;
; See also:
; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
mov_MEM_FAC1:
sty INDEX+1
sta INDEX+0
; FALLTHROUGH to get_FAC1_via_INDEX
src/basic/math_mov/bba6.get_FAC1_via_INDEX.s
+45
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@@ -0,0 +1,45 @@
;; #LAYOUT# STD * #TAKE
;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
; Math package - Mov MEM to FAC1 with address in INDEX zero page register
;
; See also:
; - https://sourceforge.net/p/acme-crossass/code-0/38/tree/trunk/ACME_Lib/cbm/c64/float.a?force=True
;
get_FAC1_via_INDEX:
; Copy the mantissa
ldy #$04
lda (INDEX), y
sta FAC1_mantissa+3
dey
lda (INDEX), y
sta FAC1_mantissa+2
dey
lda (INDEX), y
sta FAC1_mantissa+1
dey
lda (INDEX), y
sta FAC1_sign
ora #$80 ; clear the sign bit
sta FAC1_mantissa+0
; Copy the exponent
dey
lda (INDEX), y
sta FAC1_exponent
; Set low order mantissa to 0 - this should give the
; most precision while operating on integers
sty FACOV
rts
src/basic/,stubs_math/bba6.interop → src/basic/math_mov/bba6.interop
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File renamed without changes.
src/basic/math_mov/mov_MEM_FAC1.s
-79
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@@ -1,79 +0,0 @@
;; #LAYOUT# STD * #TAKE
;; #LAYOUT# * BASIC_0 #TAKE
;; #LAYOUT# * * #IGNORE
; Math package - fetch FAC1 from RAM location
;
; Input:
; - .A - address low byte
; - .Y - address high byte
;
; Output:
; - .A - FAC1 exponent, affects status flags
; - .Y - always 0
;
; Preserves:
; - .X - (experimentation with original ROM)
;
; See also:
; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
; XXX test this
mov_MEM_FAC1:
; Original routines use $22/$23 location for a vector too, see here:
; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
sty INDEX+1
sta INDEX+0
; Now copy the data from RAM to FAC2, for the format description see:
; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic#Representation_in_the_C-64
; Copy the mantissa
ldy #$04
lda (INDEX), y
sta FAC1_mantissa+3
dey
lda (INDEX), y
sta FAC1_mantissa+2
dey
lda (INDEX), y
sta FAC1_mantissa+1
dey
lda (INDEX), y
ora #$80 ; clear the sign bit
sta FAC1_mantissa+0
; Copy the sign
lda (INDEX), y
bpl @1 ; assumption: non-negative numbers are more frequent
lda #$FF
+skip_2_bytes_trash_nvz
@1:
lda #$00
sta FAC1_sign
; Copy the exponent
dey
lda (INDEX), y
sta FAC1_exponent
; Set low order mantissa to 0 - this should give the
; most precision while operating on integers
sty FACOV
; Return the FAC1 exponent
lda FAC1_exponent
rts