From c5b0d5f64b730cee30d0eb25edc33c6d0220755e Mon Sep 17 00:00:00 2001
From: hugova <hugova@kth.se>
Date: Sun, 29 Jun 2025 10:23:41 +0200
Subject: [PATCH] Remove set flag instruction to optimize circledraw from 5846
 to 5640 cpu cycles

---
 wip-hugo/routines/circle/circle.s | 47 ++++++++++++++++---------------
 1 file changed, 25 insertions(+), 22 deletions(-)

diff --git a/wip-hugo/routines/circle/circle.s b/wip-hugo/routines/circle/circle.s
index 57df4ed..d8e50af 100644
--- a/wip-hugo/routines/circle/circle.s
+++ b/wip-hugo/routines/circle/circle.s
@@ -32,7 +32,7 @@ draw_center_px_in_circle:
 
 
 draw_right_px_in_circle:
-        CLC
+        ;; C = 0, because Mult_16
         LDA X_pos
         ADC radius
         STA X_pos
@@ -41,6 +41,7 @@ draw_right_px_in_circle:
         JSR pixel_draw
         ;; This sets byte_to_paint, btp_mem_pos and Y
 
+        SEC ;; See draw_pixel_inv
 while_x_bigger_then_y:
 
 
@@ -50,7 +51,7 @@ draw_pixel:
         STA (btp_mem_pos), Y
 
 draw_pixel_inv:
-        SEC
+        ;;C = 1 beacause the branching to while_x_bigger_then_y and SEC on first ittteration.
         LDA btp_mem_pos_center_two
         SBC btp_mem_pos
         STA btp_mem_pos_inv
@@ -58,26 +59,26 @@ draw_pixel_inv:
         SBC btp_mem_pos + 1
         STA btp_mem_pos_inv + 1
 
-;; calculate the inverted y value Y = 7-Y
-STY temp
-LDA #$07
-SEC
-SBC temp
-TAY
+        ;; calculate the inverted y value Y = 7-Y
+        STY temp
+        LDA #$07
+        ;; C = 1 because arithmatic above
+        SBC temp
+        TAY
 
 ;; calculate byte_to_paint_inv 00000001 --> 10000000, 00000010 --> 01000000 ... etc
 ;; uses a table!
-        stx temp_
-        ldx byte_to_paint
+        STX temp_
+        LDX byte_to_paint
 	LDA inverse_factor_value, X;; (see END.s)
-	ldx temp_
+	LDX temp_
 
-; A = byte_to_paint_inv
+	; A = byte_to_paint_inv
         ORA (btp_mem_pos_inv), Y
         STA (btp_mem_pos_inv), Y
 
-;;Recover the Y value (we changed it because evrything is inverted)
-ldy temp
+        ;;Recover the Y value (we changed it because evrything is inverted)
+        LDY temp
 
 increment_y_pos:
         INC Y_rel ; y++
@@ -88,8 +89,9 @@ increment_y_pos:
 move_8px_down:
         LDY #$00
         ;; Switch to chunk bellow
-        ; So we subtract  #$4000
-        Add_16 btp_mem_pos, btp_mem_pos + 1, #$40, #$01 ;+320
+        ; So we subtract  #$4001
+        ; C = 1 because branching!
+        Add_16 btp_mem_pos, btp_mem_pos + 1, #$3F, #$01, ! ;+320
 increment_y_pos_end:
 
         ;;t1 += y
@@ -111,12 +113,13 @@ decrement_x_pos:
         ASL byte_to_paint
         BCC decrement_x_pos_end
 move_8px_left:
-;; Next chunk is 8 addresses away. Look in pixel_draw for more detail.
-;; -8.
-Sub_16 btp_mem_pos, btp_mem_pos + 1, #$08, #$00
-;; Restores byte to paint
-LDA #%00000001
-STA byte_to_paint
+        ;; Next chunk is 8 addresses away. Look in pixel_draw for more detail.
+        ;; -8.
+        ;; C = 1 because branching
+        Sub_16 btp_mem_pos, btp_mem_pos + 1, #$08, #$00, !
+        ;; Restores byte to paint
+        LDA #%00000001
+        STA byte_to_paint
 decrement_x_pos_end:
         LDA t2
         STA t1    ; t1 = t2