From 8d7e5662f08dada2f88fa03b6129fb0eb3119de0 Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Thu, 3 Nov 2022 15:16:19 -0400
Subject: Micro-optimizations.

---
 dla.s | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/dla.s b/dla.s
index 927acb8..4b2be32 100644
--- a/dla.s
+++ b/dla.s
@@ -531,17 +531,20 @@ checkbounds:
  beq oob
  cmp max_x
  beq oob
- sta cursor_x
+ ;sta cursor_x
  lda part_y
  cmp min_y
  beq oob
  cmp max_y
  beq oob
- sta cursor_y
+ ;sta cursor_y
+ ; checkbounds is 30 cycles when the pixel is in bounds.
+ ; I think we can beat this.
 
+checkneigh:
  ; check neighbors. used to be a subroutine, inlined it.
  ; also inlined plotsetup here.
- ldx cursor_y
+ ldx part_y
  lda lineaddrs_l,x
  sta pixptr
  lda lineaddrs_h,x
@@ -550,7 +553,7 @@ checkbounds:
  ; 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 cursor_x
+ ldx part_x
  lda fastmasks,x
  beq slow_x
  ldy xoffsets,x
@@ -570,13 +573,13 @@ slow_x:
  bne stick
 check_y:
  ; (0,-1)
- ldx cursor_y        ;3
+ ldx part_y        ;3
  lda lineaddrs_l-1,x ;5
  sta pixptr          ;3
  lda lineaddrs_h-1,x ;5
  sta pixptr+1        ;3
                      ;=19
- ldx cursor_x
+ ldx part_x
  ldy xoffsets,x
  lda xmasks,x
  sta pixmask
-- 
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