Update round_FAC1

STATUS.md

@@ -237,7 +237,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$BBFC`   | `mov_FAC2_FAC1`        | DONE     | From the Microsoft BASIC, original name: MOVFA     |
 | `$BC0C`   | `mov_r_FAC1_FAC2`      | DONE     | From the Microsoft BASIC, original name: MOVAF     |
 | `$BC0F`   | `mov_FAC1_FAC2`        | DONE     | From the Microsoft BASIC, original name: MOVEF     |
-| `$BC1B`   | `round_FAC1`           | PARTIAL  | not fully tested yet                               |
+| `$BC1B`   | `round_FAC1`           | DONE     | From the Microsoft BASIC, original name: ROUND     |
 | `$BC2B`   | `sgn_FAC1_A`           | DONE     | From the Microsoft BASIC, original name: SIGN      |
 | `$BC39`   | `sgn_FAC1`             | DONE     | From the Microsoft BASIC, original name: SGN       |
 | `$BC3C`   | `convert_A_to_FAC1`    | DONE     | From the Microsoft BASIC, original name: FLOAT     |

src/basic/math/bc1b.round_FAC1.jmp.s

@@ -1,10 +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
-
-round_FAC1:
-	jmp round_FAC1_impl
-	

src/basic/math/bc1b.round_FAC1.s

@@ -0,0 +1,33 @@
+;; #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 - rounds FAC1 before copying
+;
+; This is verified to be identical to the original Microsoft implementation where it was named ROUND.
+;
+; Alternative entry point: INCRND to increment mantissa and normalize if carry
+;
+; See also:
+; - [CM64] Computes Mapping the Commodore 64 - page 115
+; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
+;
+
+
+round_FAC1:
+
+    lda FAC1_exponent   ; Zero?
+    beq MOVRTS          ; Yes. Done rounding
+    asl FACOV           ; ROUND?
+    bcc MOVRTS          ; No. MSB off.
+INCRND:
+    jsr inc_FAC1        ; Yes, add one to LSB
+    bne MOVRTS          ; No carry means done
+    jmp RNDSHF          ; Squeeze MSB in and RTS
+                        ; CF=1 since inc_FAC1 doesn't touch CF

src/basic/math/round_FAC1.s

@@ -1,61 +0,0 @@
-;; #LAYOUT# STD *       #TAKE
-;; #LAYOUT# *   BASIC_0 #TAKE
-;; #LAYOUT# *   *       #IGNORE
-
-;
-; Math package - rounds FAC1 before copying
-;
-; See also:
-; - [CM64] Computes Mapping the Commodore 64 - page 115
-; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
-;
-
-; XXX test this
-
-round_FAC1_impl:
-
-	; If number is 0, do not do anything
-
-	lda FAC1_exponent
-	beq round_FAC1_done
-
-	lda FACOV
-	bpl round_FAC1_zero_FACOV          ; branch if it is enough to clear FACOV
-
-	; Increment the 4 bytes of matissa
-
-	; Curse you, who invented this format! Had the mantissa been little endian,
-	; we could have used INW on 65C02 and above, the code would have been smaller!
-
-	inc FAC1_mantissa+3
-	bne round_FAC1_zero_FACOV
-	inc FAC1_mantissa+2
-	bne round_FAC1_zero_FACOV
-	inc FAC1_mantissa+1
-	bne round_FAC1_zero_FACOV
-	inc FAC1_mantissa+0
-	bne round_FAC1_zero_FACOV
-
-	; If we are here, it means mantissa is 0; put it to minimum allowed and increment exponent
-
-	lda #$80
-	sta FAC1_mantissa+0
-	inc FAC1_exponent
-	bne round_FAC1_zero_FACOV
-
-	; If we are here, it means the exponent wrapped around to $00; put it back to $FF
-
-	dec FAC1_exponent
-
-	; FALLTROUGH
-
-round_FAC1_zero_FACOV:
-
-	lda #$00
-	sta FACOV
-
-	; FALLTROUGH
-
-round_FAC1_done:
-
-	rts

src/basic/math_mov/bc0f.mov_FAC1_FAC2.s

@@ -38,4 +38,5 @@ mov_FAC1_FAC2:
     dex
     bne @1
     stx FACOV           ; Always zero
+MOVRTS:
     rts

tools/similarity.c

@@ -20,7 +20,7 @@ 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,
@@ -28,8 +28,7 @@ unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {
     0xB849, 0xB97D,
     0xB983, 0xB9BB,
     0xBA8C, 0xBAB6,
-    0xBB8F, 0xBC1A,
+    0xBB8F, 0xBCF2,
-    0xBC2B, 0xBCF2,
 };