Pushed performance improvement from line_down to line_up

wip-hugo/routines/line/line_up.s

@@ -43,7 +43,11 @@ end_selfmod:
         jsr pixel_draw
         Sub_16 >btp_mem_pos, <btp_mem_pos, #$01, #$00 ;; Y has always a offset of at least 1
         LDY #$01
-        LDX X_pos
+        ;; X = X_end - X_pos
+        LDA X_end
+        SEC
+        SBC X_pos
+        TAX
 for_x:
         LDA byte_to_paint
         ORA (>btp_mem_pos), Y
@@ -56,8 +60,8 @@ move_8px_left:
         LDA #%10000000
         STA byte_to_paint
 increment_pixel_x_end:
-        INX
-        CPX X_end
+        DEX
+        ;CPX X_end
         BEQ end
         Lag_16 >D, <D, #$00, #$02, case_2
 case_1: