From 2afeab21dbcfb1b0e2bcfadc146d061347d2c94e Mon Sep 17 00:00:00 2001
From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Thu, 20 Mar 2008 14:19:46 -0400
Subject: [PATCH] Clean up and turn the iout and rout into twos comp.  I think
 this made our slice count a little worse, but oh well. 4709 postsynth

---
 Main.v | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/Main.v b/Main.v
index 2ae7962..ccc11c7 100644
--- a/Main.v
+++ b/Main.v
@@ -121,7 +121,7 @@ module MandelUnit(
 	wire bigsum_ovf, rin_ovf, iin_ovf, throwaway;
 
 	reg [12:0] xd, yd;
-	reg rd, id;
+	reg ineedbaild;
 	reg xsd, ysd;
 	reg [7:0] ibaild, curiterd;
 
@@ -133,11 +133,13 @@ module MandelUnit(
 
 	assign bigsum = r2 + i2;
 	assign bigsum_ovf = bigsum[15] | bigsum[14];
-	assign rin_ovf = rd;
-	assign iin_ovf = id;
+	
 	assign twocdiff = r2 - i2;
 	assign diff = twocdiff[15] ? -twocdiff : twocdiff;
 	assign dsign = twocdiff[15];
+	
+	wire [15:0] twocrout = xd - diff;
+	wire [15:0] twociout = yd - ri;
 
 	always @ (posedge clk)
 	begin
@@ -151,28 +153,29 @@ module MandelUnit(
 		ysout <= ysd;
 		ibaild <= ibail;
 		curiterd <= icuriter;
-		rd <= r[13] | r[14];
-		id <= i[13] | i[14];
+		ineedbaild <= r[13] | r[14] | i[13] | i[14];
 
+		// r^2 - i^2 + x
 		if (xsd ^ dsign) begin
-			if (diff > xd) begin
-				rout <= diff - xd;
+			if (twocrout[15]) begin	// diff > xd
+				rout <= -twocrout;
 				rsout <= dsign;
 			end else begin
-				rout <= xd - diff;
+				rout <= twocrout;
 				rsout <= xsd;
 			end
 		end else begin
 			rout <= diff + xd;
-			rsout <= xsd;
+			rsout <= xsd;	// xsd == dsign
 		end
 		
+		// 2 * r * i + y
 		if (ysd ^ risign) begin
-			if (ri > yd) begin
-				iout <= ri - yd;
+			if (twociout[15]) begin	// ri > yd
+				iout <= -twociout;
 				isout <= risign;
 			end else begin
-				iout <= yd - ri;
+				iout <= twociout;
 				isout <= ysd;
 			end
 		end else begin
@@ -182,7 +185,7 @@ module MandelUnit(
 		
 		// If we haven't bailed out, and we meet any of the bailout conditions,
 		// bail out now.  Otherwise, leave the bailout at whatever it was before.
-		if ((ibaild == 255) && (bigsum_ovf | rin_ovf | iin_ovf))
+		if ((ibaild == 255) && (bigsum_ovf | ineedbaild))
 			obail <= curiterd;
 		else
 			obail <= ibaild;
@@ -423,8 +426,6 @@ module MandelTop(
 	wire [2:0] mandelr, mandelg, logor, logog;
 	wire [1:0] mandelb, logob;
 	
-	
-
 	SyncGen sync(pixclk, vs, hs, x, y, realx, realy, border);
 	Mandelbrot mandel(mclk, pixclk, x, y, xofs, yofs, cycle ? colorcycle : 0, scale, mandelr, mandelg, mandelb);
 	Logo logo(pixclk, realx, realy, logoenb, logor, logog, logob);
-- 
2.43.0