Revert "Optimization"

This reverts commit af525a26fe.

gscats.s

@@ -30,7 +30,6 @@ mainBank2:
 	jsr colorFill
 
 	jsr generateTerrain
-	jsr computeScrollClipBoundaries
 
 mainGameLoop:
 	ldy mapScrollPos
@@ -108,7 +107,7 @@ kbdScanSpace:
 basePalette:
 	.word $0800,$0080,$0000,$000F,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000
 mapScrollPos:	; 4-pixel columns distance from right terrain edge
-	.word 0
+	.word 80
 quitRequested:
 	.word $0000
 

terrain.s

@@ -13,9 +13,6 @@ MAXTERRAINHEIGHT = 100	; In pixels
 ;
 ; No stack operations permitted here!
 ;
-; Initial implementation: 535 cycles per row
-; Current implementation: 443 cycles per row
-;
 renderTerrain:
 	lda #199*2
 	sta <ROWINDEX
@@ -65,14 +62,15 @@ renderClippedSpanChain:
 	lda #renderClippedSpanChainRenderNext	; 2
 	sta renderSpanComplete+1		; 4
 
-	; Look up right edge clipping data from precalculated table
+	; Find right edge of screen within span chains
-	; = 15 cycles per row
+	; = 27 cycles per skipped span
 renderClippedSpanChainLoop:
-	lda <MAPSCROLLPOS		; 3
+
-	asl						; 2
+	lda spanChain,y		; 4
-	tax						; 2
+	sec					; 2
-	ldy scrollClipIndices,x	; 4
+	sbc <RIGHTEDGE		; 3
-	lda	scrollClipIndices+2,x ; 4
+	bmi renderClippedSpanChainNextSpan	; 2/3
+	beq renderClippedSpanChainNextSpan	; 2/3
 
 renderClippedSpanChainLoop2:
 	; Now render spans until left edge of screen
@@ -93,6 +91,7 @@ renderSpanComplete:
 	; unrolled span rendering blocks
 	jmp renderClippedSpanChainRenderNext	; 3
 
+
 renderClippedSpanChainRenderNext:
 	; Track remaining words until left edge
 	; = 26 cycles per span rendered
@@ -109,6 +108,16 @@ renderClippedSpanChainRenderNext:
 	lda spanChain,y		; 5
 	bra renderClippedSpanChainLoop2	; 3
 
+renderClippedSpanChainNextSpan:
+	; Track remaining distance from right edge and
+	; continue searching for visible right edge
+	eor #$ffff			; 2
+	inc					; 2
+	sta <RIGHTEDGE		; 3
+	dey					; 2
+	dey					; 2
+	bra renderClippedSpanChainLoop	; 3
+
 renderClippedSpanChainLastSpan:
 	; Render visible portion of last visible span
 	; = 26 cycles per row
@@ -142,75 +151,6 @@ spanColors:
 spanChainIndex:
 	.word 0
 
-
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-; computeScrollClipBoundaries
-;
-; Generates a table of the clipped span indices for the right edge
-; at every possible scroll position
-;
-computeScrollClipBoundaries:
-	SAVE_AXY
-
-	lda #0
-	sta <MAPSCROLLPOS
-
-computeScrollClipBoundariesOuterLoop:
-	; Prepare our state
-	lda #80					; 2
-	sta <XLEFT				; 3
-	ldy #spanChainEnd-spanChain-2	; 2
-	lda <MAPSCROLLPOS				; 3
-	sta <RIGHTEDGE					; 3
-
-	; Find right edge of screen within span chains
-computeScrollClipBoundariesInnerLoop:
-
-	lda spanChain,y		; 4
-	sec					; 2
-	sbc <RIGHTEDGE		; 3
-	bmi computeScrollClipBoundariesNextSpan	; 2/3
-	beq computeScrollClipBoundariesNextSpan	; 2/3
-
-	; Y now contains the pointer to span that will be clipped at this scroll position
-	; A now contains remaining words of clipped span to render
-	; Write these values into our tuple data structure
-	pha
-	ldx <MAPSCROLLPOS
-	txa
-	asl
-	tax
-	tya
-    sta scrollClipIndices,x
-	inx
-	inx
-	pla
-	sta scrollClipIndices,x
-
-	; On to the next scroll position
-	lda <MAPSCROLLPOS
-	inc
-	inc
-	cmp #(TERRAINWIDTH-320)/4+2
-	beq computeScrollClipBoundariesDone
-	sta <MAPSCROLLPOS
-	bra computeScrollClipBoundariesOuterLoop
-
-computeScrollClipBoundariesNextSpan:
-	; Track remaining distance from right edge and
-	; continue searching for visible right edge
-	eor #$ffff			; 2
-	inc					; 2
-	sta <RIGHTEDGE		; 3
-	dey					; 2
-	dey					; 2
-	bra computeScrollClipBoundariesInnerLoop	; 3
-
-computeScrollClipBoundariesDone:
-	RESTORE_AXY
-	rts
-
-
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ; generateTerrain
 ;
@@ -246,14 +186,9 @@ generateTerrainLoop:
 
 terrainData:
 	.repeat TERRAINWIDTH/2
-	.word 0
+	.byte 0
 	.endrepeat
 
-scrollClipIndices:
-	; Tuples: (Clipped span, Words to Render)
-	.repeat (TERRAINWIDTH-320)/4+2	; Always scroll by two words
-	.word 0
-	.endrepeat
 
 .if 0
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;