Move logic outside loop for performance reasons.

Same as earlier commit but for line_down_inv.s, line_up.s
Comment: Should do the same for line_up_inv.s

wip-hugo/routines/memory/line_down.s

@@ -14,7 +14,7 @@
     Y_pos = $FB
     dx = $0c
     dy_2 = $0607
-    V = $0809 ;Lets reuse dx register ($08)
+    V = $0809
     D = $0a0b
 
     ;example values ~~~~~ SHOULD BE PRECOMPILED

wip-hugo/routines/memory/line_down_inv.s

@@ -12,14 +12,11 @@
     Y_end = $05
     X_pos = $FC
     Y_pos = $FB
+    dy = $0c
     dx_2 = $0607
-    dy = $08
+    V = $0809
     D = $0a0b
 
-    ;;Set values
-    LDA #$00
-    STA $FD ; for pixel_draw
-
     ;example values ~~~~~ SHOULD BE PRECOMPILED
     LDA #$00
     STA X_pos
@@ -31,23 +28,33 @@
     STA Y_end
     ;;~~~~~~~~~~
 
-    ;;2*dx = 2*(X_end -X_pos)
+    ;;We need to clear this memory
+    LDA #$00
+    STA <V
+    STA <dx_2
+    STA $FD ; for pixel_draw
+
+    ;; V = 2*(dy -dx)
+    ;; where: dy = Y_end - Y_start, dx = X_end - X_start
     LDA X_end
     SEC
     SBC X_pos
-    STA >dx_2
+    STA >V
-    LDA #$00
+    STA >dx_2;  >dx_2 = dx. Needed for dx_2 (not for V)
-    STA <dx_2
-    mult_16 >dx_2, <dx_2
-
-    ;;dy = (Y_end -Y_pos)
     LDA Y_end
     SEC
     SBC Y_pos
     STA dy
+    SEC
+    SBC >V
+    STA >V; <V = dy - dx
+    mult_16 >V, <V; V = 2*(dy -dx)
 
-    ;;D = 2*dx - dy + 2*255. 0 <=D <= 4*255
+    ;dx_2 = dx*2
-    ;;Our D is bigger then wikipedia to not use negative numbers
+    mult_16 >dx_2, <dx_2
+
+    ;;D = 2*dy - dx + 2*255
+    ;;Our D is bigger then wikipedia because D is unsigned.
     LDA >dx_2
     STA >D
     LDA <dx_2
@@ -55,13 +62,6 @@
     Add_16 >D, <D, #$00, #$01
     Sub_16 >D, <D, dy, #$00
 
-
-    ;;We wont use dy, only 2*dy from now on
-    dy_2 = $0809 ;Lets reuse dy register ($08)
-    LDA #$00
-    STA <dy_2
-    mult_16 >dy_2, <dy_2
-
 for_y:
     jsr pixel_draw
     ;;Increment Y until Y_pos = Y_end and X_pos = X_end
@@ -76,12 +76,10 @@ for_y:
     BEQ case_2
 case_1:
     INC X_pos
-    ;; D = D - 2*dx
+    Sub_16 >D, <D, >V, <V; D = D - V
-    Sub_16 >D, <D, >dy_2, <dy_2
+    JMP for_y
 case_2:
-    ;;D = D + 2*dy
+    Add_16 >D, <D, >dx_2, <dx_2;D = D + 2*dx
-    Add_16 >D, <D, >dx_2, <dx_2
-last:
     JMP for_y
 end:
 .endproc

wip-hugo/routines/memory/line_up.s

@@ -14,13 +14,10 @@
     X_pos = $FC
     Y_pos = $FB
     dy_2 = $0607
-    dx = $08
+    dx = $0c
+    V = $0809
     D = $0a0b
 
-    ;;Set values
-    LDA #$00
-    STA $FD ; for pixel_draw
-
     ;example values ~~~~~ SHOULD BE PRECOMPILED
     LDA #$90
     STA X_pos
@@ -32,35 +29,39 @@
     STA Y_end
     ;;~~~~~~~~~~
 
-    ;;2*dy = 2*(Y_pos-Y_end)
+    ;;We need to clear this memory
-    LDA Y_pos
-    SEC
-    SBC Y_end
-    STA >dy_2
     LDA #$00
+    STA <V
     STA <dy_2
-    mult_16 >dy_2, <dy_2
+    STA $FD ; for pixel_draw
 
-    ;;dx = (X_end -X_pos)
+    ;; V = 2*(dx -dy)
-    LDA X_end
+     ;; where: dy = Y_pos - Y_end, dx = X_end - X_start
-    SEC
+     LDA Y_pos
-    SBC X_pos
+     SEC
-    STA dx
+     SBC Y_end
+     STA >V
+     STA >dy_2;  >dy_2 = dy. Needed for dy_2 (not for V)
+     LDA X_end
+     SEC
+     SBC X_pos
+     STA dx
+     SEC
+     SBC >V
+     STA >V; <V = dx - dy
+     mult_16 >V, <V; V = 2*(dx -dy)
 
-    ;;D = 2*dy - dx + 2*255. 0 <=D <= 4*255
+     ;dy_2 = dy*2
-    ;;Our D is bigger then wikipedia to not use negative numbers
+     mult_16 >dy_2, <dy_2
-    LDA >dy_2
-    STA >D
-    LDA <dy_2
-    STA <D
-    Add_16 >D, <D, #$00, #$01
-    Sub_16 >D, <D, dx, #$00
 
-    ;;We wont use dx, only 2*dx from now on
+     ;;D = 2*dy - dx + 2*255
-    dx_2 = $0809 ;Lets reuse dx register ($08)
+     ;;Our D is bigger then wikipedia because D is unsigned.
-    LDA #$00
+     LDA >dy_2
-    STA <dx_2
+     STA >D
-    mult_16 >dx_2, <dx_2
+     LDA <dy_2
+     STA <D
+     Add_16 >D, <D, #$00, #$01
+     Sub_16 >D, <D, dx, #$00
 
 for_x:
     jsr pixel_draw
@@ -76,10 +77,10 @@ for_x:
     BEQ case_2
 case_1:
     DEC Y_pos
-    Sub_16 >D, <D, >dx_2, <dx_2; D = D -2*dx
+    Sub_16 >D, <D, >V, <V; D = D - V
+    JMP for_x
 case_2:
     Add_16 >D, <D, >dy_2, <dy_2;D = D + 2*dy
-last:
     JMP for_x
 end:
 .endproc

wip-hugo/source.s

@@ -1,6 +1,6 @@
 .include "STARTUP.s"
 .include "macros/16aritmatic.s"
-.include "routines/memory/line_up_inv.s"
+.include "routines/memory/line_up.s"
 
 loop_:
 jmp loop_