Add get_FAC2_via_INDEX

STATUS.md

@@ -216,7 +216,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$BA28`   | `mul_MEM_FAC1`         | DONE     |                                                    |
 | `$BA2B`   | `mul_FAC2_FAC1`        | DONE     |                                                    |
 | `$BA8C`   | `mov_MEM_FAC2`         | DONE     |                                                    |
-| `$BA90`   | `get_FAC2_via_INDEX`   | NOT DONE |                                                    |
+| `$BA90`   | `get_FAC2_via_INDEX`   | DONE     |                                                    |
 | `$BAE2`   | `mul10_FAC1`           | DONE     |                                                    |
 | `$BAFE`   | `div10_FAC1_p`         | DONE     |                                                    |
 | `$BB0F`   | `div_MEM_FAC1`         | DONE     |                                                    |

src/basic/,stubs_math/ba90.get_FAC2_via_INDEX.s

@@ -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_FAC2_via_INDEX:
-
-	+STUB_IMPLEMENTATION

src/basic/math/ba8c.mov_MEM_FAC2.jmp.s

@@ -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_FAC2

src/basic/math_mov/ba8c.mov_MEM_FAC2.s

@@ -0,0 +1,30 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #LAYOUT# *   BASIC_0 #TAKE
+;; #LAYOUT# *   *       #IGNORE
+;
+; Math package - fetch FAC2 from memory location
+;
+; Input:
+; - .A - address low byte
+; - .Y - address high byte
+;
+; Output:
+; - .A - FAC1 exponent (yes, really - Codebase64 is right)
+; - .Y - 0 (experimentation with original ROM)
+;
+; Preserves:
+; - .X - (experimentation with original ROM)
+;
+; See also:
+; - [CM64] Computes Mapping the Commodore 64 - page 114
+; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
+; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
+;
+
+
+mov_MEM_FAC2:
+	sty INDEX+1
+	sta INDEX+0
+
+    ; FALLTHROUGH to get_FAC2_via_INDEX

src/basic/math_mov/ba90.get_FAC2_via_INDEX.s

@@ -1,36 +1,18 @@
 ;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
 ;; #LAYOUT# *   BASIC_0 #TAKE
 ;; #LAYOUT# *   *       #IGNORE
 
 ;
-; Math package - fetch FAC2 from memory location
+; Math package - Mov MEM to FAC2 with address in INDEX zero page register
-;
-; Input:
-; - .A - address low byte
-; - .Y - address high byte
-;
-; Output:
-; - .A - FAC1 exponent (yes, really - Codebase64 is right)
-; - .Y - 0 (experimentation with original ROM)
-;
-; Preserves:
-; - .X - (experimentation with original ROM)
 ;
 ; See also:
-; - [CM64] Computes Mapping the Commodore 64 - page 114
+; - https://sourceforge.net/p/acme-crossass/code-0/38/tree/trunk/ACME_Lib/cbm/c64/float.a?force=True
-; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
-; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
 ;
 
-; XXX test this
+; XXX implement, test
 
-mov_MEM_FAC2:
+get_FAC2_via_INDEX:
-
-	; 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

strings/208CBAA5

@@ -0,0 +1,3 @@
+JSR $BA8C + LDA fragment
+
+Call to well known floating point function + fragment

strings/3C208CBA

@@ -0,0 +1,3 @@
+$3C + JSR $BA8C
+
+Fragment and call to well known floating point function.

strings/4C67B8208CBAA56649FF8566

@@ -0,0 +1,5 @@
+4C 67 B8 20 8C BA A5 66 49 FF 85 66
+
+JMP $B867 + JSR $BA8C + LDA $66 + EOR #$FF + STA $66
+
+Call two well known floating point functions and invert sign of FAC1

strings/666366646665667060

@@ -0,0 +1,3 @@
+ror $63 + ror $64 + ror $65 + ror $70 + rts
+
+Shifting of 32 bit value of the FAC1 mantissa in the zero page

strings/BCA90085

@@ -0,0 +1,3 @@
+$BC + LDA #$00 + STA fragment
+
+Fragment of clearing variable in zero page

testsuite/unit/math.vs

@@ -145,6 +145,38 @@ compare $61 $66 $1001
 compare $70 $70 $1003  ; FACOV = 0
 print "END"
 
+print "TEST: mov MEM FAC2 const 1.0"
+fill $69 $6E FF FF FF FF FF AA
+r A=$BC
+r Y=$B9
+r PC=$BA8C
+ret
+fill $1001 $1006 81 80 00 00 00 00
+print "COMPARE"
+compare $69 $6E $1001
+print "END"
+
+print "TEST: mov MEM FAC2 const -0.5"
+fill $69 $6E FF FF FF FF FF AA
+r A=$E0
+r Y=$B9
+r PC=$BA8C
+ret
+fill $1001 $1006 80 80 00 00 00 FF
+print "COMPARE"
+compare $69 $6E $1001
+print "END"
+
+print "TEST: get_FAC2_via_INDEX -0.5"
+fill $69 $6E FF FF FF FF FF AA
+fill $22 $23 E0 B9
+r PC=$BA90
+ret
+fill $1001 $1006 80 80 00 00 00 FF
+print "COMPARE"
+compare $69 $6E $1001
+print "END"
+
 print "TEST: FCOMP 1.0 == 1.0"
 r A=$BC
 r Y=$B9