From d7ae2f127c09229227f91d2309bc044a49dab2b4 Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Sun, 6 Nov 2022 16:09:13 -0500
Subject: Remove dead code, save 3 cycles in drunkwalk, v0.1.3.

---
 dla.s | 73 +++++--------------------------------------------------------------
 1 file changed, 5 insertions(+), 68 deletions(-)

diff --git a/dla.s b/dla.s
index 785f3e9..3e549f5 100644
--- a/dla.s
+++ b/dla.s
@@ -461,39 +461,6 @@ plot:
  sta (pixptr),y
  rts
 
-;;; Subroutine: unplot
-;;; erases a pixel at (cursor_x, cursor_y)
-unplot:
- jsr plotsetup
- lda pixmask
- eor #$ff
- sta pixmask
- lda (pixptr),y
- and pixmask
- sta (pixptr),y
- rts
-
-;;; Subroutine: locate
-;;; check the pixel at (cursor_x, cursor_y)
-;;; if set, return with Z=0
-;;; otherwise, return with Z=1
-;;;; Inlined (keep for reference)
-;locate:
-; jsr plotsetup
-; and (pixptr),y
-; rts
-
-;;; Subroutine: spawn
-;;; Pick a random point on the edge of a circle
-;;;; Inlined (keep for reference)
-; spawn:
-;  ldy RANDOM
-;  lda (spawn_x),y
-;  sta part_x
-;  lda (spawn_y),y
-;  sta part_y
-;  rts
-
 oob:
  rts
 ;;; Subroutine: drunkwalk
@@ -551,42 +518,10 @@ selfmod_xmax = * + 1
  lda xmasks+1,x ; 4
  and (pixptr),y ; 5
  bne stick      ; 2/3
- beq check_ud    ; 3 ; still check Y neighbors.
-
-checkneigh:
- ; check neighbors. used to be a subroutine, inlined it.
- ; we only get here when the pixel has moved up or down (not left/right).
- ; also inlined plotsetup here.
- sty part_y           ; 3
- lda lineaddrs_l,y    ; 5
- sta pixptr           ; 3
- lda lineaddrs_h,y    ; 5
- sta pixptr+1         ; 3
-
- ; 3/4 of the time, we can use a faster code path, check
- ; (-1,0) and (1,0) at the same time. this happens only when
- ; both pixels lie within the same byte.
- ;ldx part_x ; X already has this from before
- lda fastmasks,x      ; 4
- beq slow_x           ; 2/3
- ldy xoffsets,x       ; 4
- and (pixptr),y       ; 5
- bne stick            ; 2/3
- beq check_ud          ; 2/3
-slow_x:
- ; (-1,0)
- ldy xoffsets-1,x     ; 4
- lda xmasks-1,x       ; 4
- and (pixptr),y       ; 5
- bne stick            ; 2/3
- ; (1,0)
- ldy xoffsets+1,x     ; 4
- lda xmasks+1,x       ; 4
- and (pixptr),y       ; 5
- bne stick            ; 2/3
+ ; fall through to check_ud
 
 check_ud:
- ; this happens no matter what direction the pixel moved.
+ ; this happens when the pixel moved left or right.
  ; (0,-1)
  ; subtract 32 (one line) from the pointer. one cycle faster
  ; than reloading from lineaddrs_l/h table.
@@ -616,6 +551,7 @@ stick: ; we always get here with Z flag clear
  stx part_x ; only update part_x at exit.
  rts
 
+ ; this happens when the pixel moved up.
 check_lru:
  sty part_y           ; 3
  lda lineaddrs_l,y    ; 5
@@ -665,6 +601,7 @@ check_u:
  jmp dwloop           ; 3 ; too far for a branch
 
 
+ ; this happens when the pixel moved down.
 check_lrd:
  sty part_y           ; 3
  lda lineaddrs_l,y    ; 5
@@ -868,7 +805,7 @@ ci_done:
 ; banner and saveprompt must start with a clear-screen code.
 banner:
  .byte $7d, "Diffusion Limited Aggregate",$9b
- .byte "Urchlay's ASM version 0.1.2",$9b,$9b
+ .byte "Urchlay's ASM version 0.1.3",$9b,$9b
  .byte "Particle count range: 1 to 65535",$9b
  .byte "How many particles [",$0
 
-- 
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