From fae8055928a76a508f92accf10de633acd2aef25 Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sun, 5 May 2019 03:28:20 +0100
Subject: [PATCH] add integer function unit

---
 src/scoreboard/int_fn_unit.py | 126 ++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 src/scoreboard/int_fn_unit.py

diff --git a/src/scoreboard/int_fn_unit.py b/src/scoreboard/int_fn_unit.py
new file mode 100644
index 00000000..a22dbd39
--- /dev/null
+++ b/src/scoreboard/int_fn_unit.py
@@ -0,0 +1,126 @@
+from nmigen.compat.sim import run_simulation
+from nmigen.cli import verilog, rtlil
+from nmigen import Module, Signal, Elaboratable
+from nmutil.latch import SRLatch
+from nmigen.lib.coding import Decoder
+
+
+class IntFnUnit(Elaboratable):
+    """ implements 11.4.7 integer function unit, p37
+    """
+    def __init__(self, wid):
+        self.reg_width = wid
+
+        # inputs
+        self.dest_i = Signal(wid, reset_less=True) # Dest in (top)
+        self.src1_i = Signal(wid, reset_less=True) # oper1 in (top)
+        self.src2_i = Signal(wid, reset_less=True) # oper2 in (top)
+        self.issue_i = Signal(reset_less=True)    # Issue in (top)
+
+        self.go_write_i = Signal(reset_less=True) # Go Write in (left)
+        self.go_read_i = Signal(reset_less=True)  # Go Read in (left)
+        self.req_rel_i = Signal(wid, reset_less=True)  # request release (left)
+
+        self.g_rd_pend_i = Signal(wid, reset_less=True)  # global rd (right)
+        self.g_wr_pend_i = Signal(wid, reset_less=True)  # global wr (right)
+
+        # outputs
+        self.readable_o = Signal(reset_less=True) # Readable out (right)
+        self.writable_o = Signal(reset_less=True) # Writable out (right)
+
+        self.rd_pend_o = Signal(wid, reset_less=True) # rd pending (right)
+        self.wr_pend_o = Signal(wid, reset_less=True) # wr pending (right)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.submodules.rd_l = rd_l = SRLatch()
+        m.submodules.wr_l = wr_l = SRLatch()
+        m.submodules.dest_d = dest_d = Decoder(self.reg_width)
+        m.submodules.src1_d = src1_d = Decoder(self.reg_width)
+        m.submodules.src2_d = src2_d = Decoder(self.reg_width)
+
+        # go_write latch: reset on go_write HI, set on issue
+        m.d.comb += wr_l.s.eq(self.issue_i)
+        m.d.comb += wr_l.r.eq(self.go_write_i)
+
+        # src1 latch: reset on go_read HI, set on issue
+        m.d.comb += rd_l.s.eq(self.issue_i)
+        m.d.comb += rd_l.r.eq(self.go_read_i)
+
+        # dest decoder: write-pending out
+        m.d.comb += dest_d.i.eq(self.dest_i)
+        m.d.comb += dest_d.n.eq(wr_l.q) # FIXME this is sync-delayed!
+        m.d.comb += self.wr_pend_o.eq(dest_d.o)
+
+        # src1/src2 decoder: read-pending out
+        m.d.comb += src1_d.i.eq(self.src1_i)
+        m.d.comb += src1_d.n.eq(rd_l.q) # FIXME this is sync-delayed!
+        m.d.comb += src2_d.i.eq(self.src2_i)
+        m.d.comb += src2_d.n.eq(rd_l.q) # FIXME this is sync-delayed!
+        m.d.comb += self.rd_pend_o.eq(src1_d.o | src2_d.o)
+
+        # readable output signal
+        int_g_wr = Signal(self.reg_width, reset_less=True)
+        m.d.comb += int_g_wr.eq(self.g_wr_pend_i & self.rd_pend_o)
+        m.d.comb += self.readable_o.eq(int_g_wr.bool())
+
+        # writable output signal
+        int_g_rw = Signal(self.reg_width, reset_less=True)
+        g_rw = Signal(reset_less=True)
+        m.d.comb += int_g_rw.eq(self.g_rd_pend_i & self.wr_pend_o)
+        m.d.comb += g_rw.eq(~int_g_rw.bool())
+        m.d.comb += self.writable_o.eq(g_rw & rd_l.q & self.req_rel_i)
+
+        return m
+
+    def __iter__(self):
+        yield self.dest_i
+        yield self.src1_i
+        yield self.src2_i
+        yield self.issue_i
+        yield self.go_write_i
+        yield self.go_read_i
+        yield self.req_rel_i
+        yield self.g_rd_pend_i
+        yield self.g_wr_pend_i
+        yield self.readable_o
+        yield self.writable_o
+        yield self.rd_pend_o
+        yield self.wr_pend_o
+
+    def ports(self):
+        return list(self)
+
+
+def int_fn_unit_sim(dut):
+    yield dut.dest_i.eq(1)
+    yield dut.issue_i.eq(1)
+    yield
+    yield dut.issue_i.eq(0)
+    yield
+    yield dut.src1_i.eq(1)
+    yield dut.issue_i.eq(1)
+    yield
+    yield
+    yield
+    yield dut.issue_i.eq(0)
+    yield
+    yield dut.go_read_i.eq(1)
+    yield
+    yield dut.go_read_i.eq(0)
+    yield
+    yield dut.go_write_i.eq(1)
+    yield
+    yield dut.go_write_i.eq(0)
+    yield
+
+def test_int_fn_unit():
+    dut = IntFnUnit(32)
+    vl = rtlil.convert(dut, ports=dut.ports())
+    with open("test_int_fn_unit.il", "w") as f:
+        f.write(vl)
+
+    run_simulation(dut, int_fn_unit_sim(dut), vcd_name='test_int_fn_unit.vcd')
+
+if __name__ == '__main__':
+    test_int_fn_unit()
-- 
2.30.2