From 3c14f4094dde08ba304cd2a01c4549cd84879351 Mon Sep 17 00:00:00 2001
From: alpine9000 <alex.g.brown@gmail.com>
Date: Sun, 27 Mar 2016 20:03:27 +1100
Subject: [PATCH] More small optimisations

---
 024.simple_text/blittext.s | 45 +++++++++++++++-----------------------
 1 file changed, 18 insertions(+), 27 deletions(-)

diff --git a/024.simple_text/blittext.s b/024.simple_text/blittext.s
index b302c01..3f3b7d2 100644
--- a/024.simple_text/blittext.s
+++ b/024.simple_text/blittext.s
@@ -53,20 +53,13 @@ DrawChar8:
 	add.w	#1,d5		; while we have a weird font image, '!' starts on second line
 	move.l	d6,a1		; #font
 	mulu.w	#SCREEN_WIDTH_BYTES*SCREEN_BIT_DEPTH*FONT_HEIGHT,d5
+
 	if	MASKED_FONT==1
 	move.l	d7,a2		; #fontMask
 	add.w	d5,a2		; add y offset in lines to fontMask address
 	endif
+
 	add.w	d5,a1		; add y offset in lines to font address
-	
-	btst	#0,d2		; blitter does words only, so we need to know if its an odd or even character
-	beq	.even		; then shift it into position with the blitter shift
-.odd:				; this check is repeated in .blitChar8 so should be refactored
-	moveq	#1,d3		
-	bra	.c1
-.even:	
-	moveq	#0,d3
-.c1:
 
 	add.w	d2,a1		; add offset into font
 	if MASKED_FONT==1
@@ -74,24 +67,24 @@ DrawChar8:
 	endif
 
 .blitChar8:
-	;; kills a4,d2,d4	
+	;; kills a4,d2,d4,d5
 	;; d0 - xpos
 	;; d1 - ypos bytes
-	;; d3 - odd character = 1, even character = 0
+	;; d2.0 - odd character = 1, even character = 0
 	;; a4 - display
 	;; a1 - object
 	;; a2 - mask	
 
  	move.l	d0,d4
- 	move.l	d0,d2	
+ 	move.l	d0,d5	
 	lsr.w	#3,d4					; d4 = XPOS_BYTES
 	
 	WaitBlitter
 	
-	btst	#0,d3
+	btst	#0,d2
 	beq	.evenChar
 .oddChar
-	subq	#8,d2
+	subq	#8,d5					; offset the x position for the odd character
 	move.w	#$00FF,BLTAFWM(a6)			; select the second (odd) character in the word
 
 	subq	#1,a4	
@@ -100,29 +93,27 @@ DrawChar8:
 	move.w	#$FF00,BLTAFWM(a6)			; select the first character in the word
 .continue:
 
-	;; this shift will give us the bits to shift (bits 0-3) in bits (12-15) of d2
-	lsl.w	#8,d2					; BLIT_SOURCE_SHIFT<<BLIT_ASHIFTSHIFT
-	lsl.w	#4,d2 					; BLIT_SOURCE_SHIFT<<BLIT_ASHIFTSHIFT
+	;; this shift will give us the bits to shift (bits 0-3) in bits (12-15) of d5
+	lsl.w	#8,d5					; BLIT_SOURCE_SHIFT<<BLIT_ASHIFTSHIFT
+	lsl.w	#4,d5 					; BLIT_SOURCE_SHIFT<<BLIT_ASHIFTSHIFT
 	
-	move.w	d2,BLTCON1(A6)
+	move.w	d5,BLTCON1(A6)
 
 	if MASKED_FONT==1
-	ori.w   #BLIT_SRCA|BLIT_SRCB|BLIT_SRCC|BLIT_DEST|BLIT_LF_MINTERM,d2
+	ori.w   #BLIT_SRCA|BLIT_SRCB|BLIT_SRCC|BLIT_DEST|BLIT_LF_MINTERM,d5
 	move.l 	a2,BLTAPTH(a6)				; mask bitplane
 	else
-	ori.w   #BLIT_SRCB|BLIT_SRCC|BLIT_DEST|BLIT_LF_MINTERM,d2
-
+	ori.w   #BLIT_SRCB|BLIT_SRCC|BLIT_DEST|BLIT_LF_MINTERM,d5
 	endif
 
 	move.l 	a1,BLTBPTH(a6)				; source bitplane		
-	move.w	d2,BLTCON0(A6)
+	move.w	d5,BLTCON0(a6)				; set minterm, dma channel and shift
 
-	move.l 	a4,d2					; d2 = dest bitplane address
-	add.l 	d4,d2					; d2 = += XPOS_BYTES
-	add.l	d1,d2					; d2 = += YPOS_BYTES
+	add.l 	d4,a4					; dest += XPOS_BYTES
+	add.l	d1,a4					; dest += YPOS_BYTES
 
-	move.l 	d2,BLTCPTH(a6) 				; background top left corner
-	move.l 	d2,BLTDPTH(a6) 				; destination top left corner
+	move.l 	a4,BLTCPTH(a6) 				; background top left corner
+	move.l 	a4,BLTDPTH(a6) 				; destination top left corner
 
 	move.w 	#(FONT_HEIGHT*SCREEN_BIT_DEPTH)<<6|(BLIT_WIDTH_WORDS),BLTSIZE(a6)	;rectangle size, starts blit
 	rts