corelib: new putpixel routine using shifter/maskgen

lib/corelib.s

@@ -706,108 +706,32 @@ CMPWORDS_XT2:
 	.EQU FB_PS	$90C
 	.EQU FB_PD	$910
 	.EQU FB_CTL	$914
-; set a pixel in fb memory
+	.EQU FB_SHIFTER $918
-; parameters: x,y - coordinates
+	.EQU FB_SHIFTCOUNT $91C
-PUTPIXEL_1BPP:
+	.EQU FB_SHIFTERM $920
-	; calculate vmem address:
+	.EQU FB_SHIFTERSP $924
-	OVER ; duplicate x
+	.EQU FB_MASKGEN $928
-	; divide x by 32
-	SHR
-	SHR
-	SHR
-	SHR
-	SHR
-	SWAP
-	; multiply y by words per line
-	SHL 2
-	SHL 2
-	SHL
 
-	ADD ; add results together for vmem addr
+; draw a single pixel
+; args: x, y, color
 
-	DUP
-	LOADCP FB_WA
-	SWAP
-	STOREI	; store to framebuffer write addr register
-	DROP
-	LOADCP FB_RA ; and to framebuffer read addr register
-	SWAP
-	STOREI
-	DROP
-
-	; x is now at top of stack
-	; get bit value from x modulo 32
-	LOADC 31
-	AND
-	SHL 2 ; (x & 31) * 4 = offset into table
-	LOADCP INT_TO_PIX_TABLE
-	ADD
-	LOADI
-
-	LOADCP FB_IO
-	; read old vmem value
-	LOADCP FB_IO
-	LOADI
-	; or in new bit
-	OR
-	; write new value
-	STOREI
-	DROP
-
-	RET
-
-INT_TO_PIX_TABLE:
-	.WORD %10000000_00000000_00000000_00000000
-	.WORD %01000000_00000000_00000000_00000000
-	.WORD %00100000_00000000_00000000_00000000
-	.WORD %00010000_00000000_00000000_00000000
-	.WORD %00001000_00000000_00000000_00000000
-	.WORD %00000100_00000000_00000000_00000000
-	.WORD %00000010_00000000_00000000_00000000
-	.WORD %00000001_00000000_00000000_00000000
-	.WORD %00000000_10000000_00000000_00000000
-	.WORD %00000000_01000000_00000000_00000000
-	.WORD %00000000_00100000_00000000_00000000
-	.WORD %00000000_00010000_00000000_00000000
-	.WORD %00000000_00001000_00000000_00000000
-	.WORD %00000000_00000100_00000000_00000000
-	.WORD %00000000_00000010_00000000_00000000
-	.WORD %00000000_00000001_00000000_00000000
-	.WORD %00000000_00000000_10000000_00000000
-	.WORD %00000000_00000000_01000000_00000000
-	.WORD %00000000_00000000_00100000_00000000
-	.WORD %00000000_00000000_00010000_00000000
-	.WORD %00000000_00000000_00001000_00000000
-	.WORD %00000000_00000000_00000100_00000000
-	.WORD %00000000_00000000_00000010_00000000
-	.WORD %00000000_00000000_00000001_00000000
-	.WORD %00000000_00000000_00000000_10000000
-	.WORD %00000000_00000000_00000000_01000000
-	.WORD %00000000_00000000_00000000_00100000
-	.WORD %00000000_00000000_00000000_00010000
-	.WORD %00000000_00000000_00000000_00001000
-	.WORD %00000000_00000000_00000000_00000100
-	.WORD %00000000_00000000_00000000_00000010
-	.WORD %00000000_00000000_00000000_00000001
-
-PUTMPIXEL:
-	LOADC 1
-; set a pixel in fb memory
-; parameters: x,y,color - coordinates, color value (0-15)
 PUTPIXEL:
 PUTPIXEL_4BPP:
 	.EQU PUTPIXEL_X 0
 	.EQU PUTPIXEL_Y 4
 	.EQU PUTPIXEL_COLOR 8
-	.EQU PUTPIXEL_PIXPOS 12
+	.EQU PUTPIXEL_BPSAV 12
 	.EQU PUTPIXEL_FS 16
 
 	FPADJ -PUTPIXEL_FS
-
 	STORE PUTPIXEL_COLOR
 	STORE PUTPIXEL_Y
 	STORE PUTPIXEL_X
 
+	LOADREG BP
+	STORE PUTPIXEL_BPSAV
+	LOADC 0
+	STOREREG BP
 
 	; calculate vmem address: (x / 8) + (y * 80)
 	LOAD PUTPIXEL_X
@@ -826,83 +750,37 @@ PUTPIXEL_4BPP:
 
 	ADD ; add results together for vmem addr
 
-	LOADCP FB_WA
+	DUP
-	OVER
+	STORE.B FB_WA	; set as write and read addresses
-	STOREI	; store to framebuffer write addr register
+	STORE.B FB_RA
-	DROP
-	LOADCP FB_RA ; and to framebuffer read addr register
-	SWAP	; swap addr and value for STOREI
-	STOREI
-	DROP
-
-	LOAD PUTPIXEL_X
-	;		|0000.0000|0000.0000|0000.0000|0000.1111|
-	LOADC 7
-	AND		; calculate pixel position in word
-	LOADC 7
-	SWAP
-	SUB		; pixpos = 7 - (x & 7)
-	STORE PUTPIXEL_PIXPOS
 
+	; create pixel data from color value in
+	; leftmost pixel data bits (31-28)
 	LOAD PUTPIXEL_COLOR
-	LOAD PUTPIXEL_PIXPOS
+	BROT
-	SHR		; rcount = pixpos / 2
+	BROT
-ROTLOOP_:
+	BROT
-	DUP		; exit loop if rcount is 0
-	CBRANCH.Z ROTLOOP_END
-	SWAP		; pixel value is now on top of stack
-	BROT		; value = value << 8
-	SWAP		; rcount is now on top of stack
-	DEC 1		; rcount = rcount - 1
-	BRANCH ROTLOOP_
-ROTLOOP_END:
-	DROP		; drop rcount
-	; shifted pixel value is now at top of stack
-	LOAD PUTPIXEL_PIXPOS
-	LOADC 1
-	AND
-	CBRANCH.Z EVEN_PIXPOS
-	SHL 2	; if pixpos is odd, shift by 4 bits
 	SHL 2
-EVEN_PIXPOS:
+	SHL 2
-	LOAD PUTPIXEL_X
+	STORE.B FB_SHIFTER	; store pixel into shifter
-	; get bit value from x modulo 8
-	LOADC 7
-	AND
-	SHL 2 ; (x & 7) * 4 = offset into table
-	LOADCP INT_TO_MASK_TABLE
-	ADD
-	LOADI
 
-	; read old vmem value
+	LOAD PUTPIXEL_X 	; use x coord as shift count
-	LOADCP FB_IO
+	STORE.B FB_SHIFTCOUNT	; writing triggers shifting
-	LOADI
-	; mask bits
-	AND
-	; or in shifted pixel value
-	OR
 
-	; write new value
+	LOAD.B FB_SHIFTERM	; get shift result as mask
-	LOADCP FB_IO
+	LOAD.B FB_IO		; get background pixel data
-	SWAP
+	AND			; remove bits for new pixel from bg
-	STOREI
+
-	DROP
+	LOAD.B FB_SHIFTER	; load shifted pixel
+	OR			; OR in new pixel bits
+	STORE.B FB_IO		; write new pixel data word to vmem
+
+	LOAD PUTPIXEL_BPSAV
+	STOREREG BP
 
 	FPADJ PUTPIXEL_FS
 	RET
 
-	.CPOOL
-
-INT_TO_MASK_TABLE:
-	.WORD %00001111_11111111_11111111_11111111
-	.WORD %11110000_11111111_11111111_11111111
-	.WORD %11111111_00001111_11111111_11111111
-	.WORD %11111111_11110000_11111111_11111111
-	.WORD %11111111_11111111_00001111_11111111
-	.WORD %11111111_11111111_11110000_11111111
-	.WORD %11111111_11111111_11111111_00001111
-	.WORD %11111111_11111111_11111111_11110000
-
 ; draw a line between two points
 ; parameters: x0, y0, x1, y1, color
 	.EQU DL_X0 0