From c7ef75b55c5ea7d98f76556e0371d589a19dde80 Mon Sep 17 00:00:00 2001
From: Anton Blanchard <anton@ozlabs.org>
Date: Tue, 1 Feb 2022 20:52:58 +1100
Subject: [PATCH] Forgot multiply.vhdl

---
 asic/multiply.vhdl | 128 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 asic/multiply.vhdl

diff --git a/asic/multiply.vhdl b/asic/multiply.vhdl
new file mode 100644
index 0000000..a604554
--- /dev/null
+++ b/asic/multiply.vhdl
@@ -0,0 +1,128 @@
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+library work;
+use work.common.all;
+
+-- XXX We should be able to make timing with a 2 cycle multiplier
+entity multiply is
+    generic (
+        PIPELINE_DEPTH : natural := 4
+        );
+    port (
+        clk   : in std_logic;
+
+        m_in  : in MultiplyInputType;
+        m_out : out MultiplyOutputType
+        );
+end entity multiply;
+
+architecture behaviour of multiply is
+    signal m: MultiplyInputType := MultiplyInputInit;
+
+    type multiply_pipeline_stage is record
+        valid     : std_ulogic;
+        is_32bit  : std_ulogic;
+        not_res   : std_ulogic;
+    end record;
+    constant MultiplyPipelineStageInit : multiply_pipeline_stage := (valid => '0',
+                                                                     is_32bit => '0',
+                                                                     not_res => '0');
+
+    type multiply_pipeline_type is array(0 to PIPELINE_DEPTH-1) of multiply_pipeline_stage;
+    constant MultiplyPipelineInit : multiply_pipeline_type := (others => MultiplyPipelineStageInit);
+
+    type reg_type is record
+        multiply_pipeline : multiply_pipeline_type;
+    end record;
+
+    signal r, rin : reg_type := (multiply_pipeline => MultiplyPipelineInit);
+    signal overflow : std_ulogic;
+    signal ovf_in   : std_ulogic;
+
+    signal mult_out : std_logic_vector(127 downto 0);
+
+    component multiply_add_64x64 port(
+        clk : in std_logic;
+        a   : in std_logic_vector(63 downto 0);
+        b   : in std_logic_vector(63 downto 0);
+        c   : in std_logic_vector(127 downto 0);
+        o   : out std_logic_vector(127 downto 0)
+        );
+    end component;
+begin
+    multiply_0: process(clk)
+    begin
+        if rising_edge(clk) then
+            m <= m_in;
+            r <= rin;
+            overflow <= ovf_in;
+        end if;
+    end process;
+
+    multiplier : multiply_add_64x64
+        port map (
+            clk => clk,
+            a => m.data1,
+            b => m.data2,
+            c => m.addend,
+            o => mult_out
+    );
+
+    multiply_1: process(all)
+        variable v : reg_type;
+        variable d : std_ulogic_vector(127 downto 0);
+        variable d2 : std_ulogic_vector(63 downto 0);
+        variable ov : std_ulogic;
+    begin
+        v := r;
+        v.multiply_pipeline(0).valid := m.valid;
+        v.multiply_pipeline(0).is_32bit := m.is_32bit;
+        v.multiply_pipeline(0).not_res := m.not_result;
+
+        loop_0: for i in 1 to PIPELINE_DEPTH-1 loop
+            v.multiply_pipeline(i) := r.multiply_pipeline(i-1);
+        end loop;
+
+        if v.multiply_pipeline(PIPELINE_DEPTH-1).not_res = '1' then
+            d := not mult_out;
+	else
+            d := mult_out;
+        end if;
+
+        ov := '0';
+        if v.multiply_pipeline(PIPELINE_DEPTH-1).is_32bit = '1' then
+            ov := (or d(63 downto 31)) and not (and d(63 downto 31));
+        else
+            ov := (or d(127 downto 63)) and not (and d(127 downto 63));
+        end if;
+        ovf_in <= ov;
+
+        m_out.result <= d;
+        m_out.overflow <= overflow;
+        m_out.valid <= v.multiply_pipeline(PIPELINE_DEPTH-1).valid;
+
+        rin <= v;
+    end process;
+end architecture behaviour;
+
+
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity short_multiply is
+    port (
+        clk   : in std_ulogic;
+
+        a_in  : in std_ulogic_vector(15 downto 0);
+        b_in  : in std_ulogic_vector(15 downto 0);
+        m_out : out std_ulogic_vector(31 downto 0)
+        );
+end entity short_multiply;
+
+architecture behaviour of short_multiply is
+begin
+    m_out <= std_ulogic_vector(signed(a_in) * signed(b_in));
+end architecture behaviour;