From ca02833f22b08ceeeff501107371aa6667426115 Mon Sep 17 00:00:00 2001
From: Alejandro Soto <alejandro@34project.org>
Date: Sun, 5 May 2024 17:38:55 -0600
Subject: rtl/gfx: rename platform/wavelet3d -> rtl/gfx

---
 rtl/gfx/gfx_clz.sv | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 rtl/gfx/gfx_clz.sv

(limited to 'rtl/gfx/gfx_clz.sv')

diff --git a/rtl/gfx/gfx_clz.sv b/rtl/gfx/gfx_clz.sv
new file mode 100644
index 0000000..8d6f100
--- /dev/null
+++ b/rtl/gfx/gfx_clz.sv
@@ -0,0 +1,68 @@
+/* Implementación en árbol de count leading zeros (CLZ).
+ * WIDTH debe ser una potencia de 2.
+ */
+module gfx_clz
+#(int WIDTH = 0)
+(
+	input  logic                  clk,
+
+	input  logic[WIDTH - 1:0]     value,
+	output logic[$clog2(WIDTH):0] clz
+);
+
+	genvar i;
+	generate
+		if (WIDTH <= 1) begin
+			always_ff @(posedge clk)
+				clz <= !value;
+		end else if (WIDTH == 2) begin
+			always_ff @(posedge clk)
+				unique case (value)
+					2'b00: clz <= 2'b10;
+					2'b01: clz <= 2'b01;
+					2'b10: clz <= 2'b00;
+					2'b11: clz <= 2'b00;
+				endcase
+		end else if (WIDTH == 4) begin
+			// Eficiente en FPGAs con 4-LUTs
+			always_ff @(posedge clk)
+				if (value[3])
+					clz <= 3'b000;
+				else if (value[2])
+					clz <= 3'b001;
+				else if (value[1])
+					clz <= 3'b010;
+				else if (value[0])
+					clz <= 3'b011;
+				else
+					clz <= 3'b100;
+		end else begin
+			logic msb_right;
+			logic[$clog2(WIDTH) - 1:0] clz_left, clz_right;
+			logic[$clog2(WIDTH) - 2:0] tail_right;
+
+			assign {msb_right, tail_right} = clz_right;
+
+			gfx_clz #(WIDTH / 2) left
+			(
+				.clk(clk),
+				.clz(clz_left),
+				.value(value[WIDTH - 1:WIDTH / 2])
+			);
+
+			gfx_clz #(WIDTH / 2) right
+			(
+				.clk(clk),
+				.clz(clz_right),
+				.value(value[WIDTH / 2 - 1:0])
+			);
+
+			always_ff @(posedge clk)
+				if (clz_left[$clog2(WIDTH) - 1])
+					clz <= {msb_right, ~msb_right, tail_right};
+				else
+					clz <= {1'b0, clz_left};
+		end
+	endgenerate
+
+endmodule
-- 
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