From 55f611806164b5b125ddcfa4732ec8c2d735e561 Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sun, 2 Jun 2019 13:24:46 +0100
Subject: [PATCH] add MemSim, remove redundant signal

---
 src/experiment/score6600.py | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/experiment/score6600.py b/src/experiment/score6600.py
index 4c55e0bd..dd48f2d5 100644
--- a/src/experiment/score6600.py
+++ b/src/experiment/score6600.py
@@ -24,7 +24,8 @@ from math import log
 
 class Memory(Elaboratable):
     def __init__(self, regwid, addrw):
-        depth = (1<<addrw) / (regwid/8)
+        self.ddepth = regwid/8
+        depth = (1<<addrw) / self.ddepth
         self.adr   = Signal(addrw)
         self.dat_r = Signal(regwid)
         self.dat_w = Signal(regwid)
@@ -36,7 +37,7 @@ class Memory(Elaboratable):
         m.submodules.rdport = rdport = self.mem.read_port()
         m.submodules.wrport = wrport = self.mem.write_port()
         m.d.comb += [
-            rdport.addr.eq(self.adr[2:]),
+            rdport.addr.eq(self.adr[self.ddepth:]), # ignore low bits
             self.dat_r.eq(rdport.data),
             wrport.addr.eq(self.adr),
             wrport.data.eq(self.dat_w),
@@ -45,6 +46,20 @@ class Memory(Elaboratable):
         return m
 
 
+class MemSim:
+    def __init__(self, regwid, addrw):
+        self.regwid = regwid
+        self.ddepth = regwid//8
+        depth = (1<<addrw) // self.ddepth
+        self.mem = list(range(0, depth))
+
+    def ld(self, addr):
+        return self.mem[addr>>self.ddepth]
+
+    def st(self, addr, data):
+        self.mem[addr>>self.ddepth] = data & ((1<<self.regwid)-1)
+
+
 class CompUnitsBase(Elaboratable):
     """ Computation Unit Base class.
 
@@ -392,7 +407,6 @@ class Scoreboard(Elaboratable):
         m.submodules.bshadow = bshadow = ShadowMatrix(n_intfus, 1, False)
 
         # record previous instruction to cast shadow on current instruction
-        fn_issue_prev = Signal(n_intfus)
         prev_shadow = Signal(n_intfus)
 
         # Branch Speculation recorder.  tracks the success/fail state as
@@ -493,10 +507,6 @@ class Scoreboard(Elaboratable):
         for i in range(n_intfus):
             comb += shadows.s_good_i[i][0:n_intfus].eq(go_wr_o[0:n_intfus])
 
-        # work out the current-activated busy unit (by recording the old one)
-        with m.If(fn_issue_o): # only update prev bit if instruction issued
-            sync += fn_issue_prev.eq(fn_issue_o)
-
         # *previous* instruction shadows *current* instruction, and, obviously,
         # if the previous is completed (!busy) don't cast the shadow!
         comb += prev_shadow.eq(~fn_issue_o & cu.busy_o)
@@ -682,6 +692,7 @@ class IssueToScoreboard(Elaboratable):
     def ports(self):
         return list(self)
 
+
 IADD = 0
 ISUB = 1
 IMUL = 2
@@ -1080,6 +1091,7 @@ def scoreboard_sim(dut, alusim):
 def test_scoreboard():
     dut = IssueToScoreboard(2, 1, 1, 16, 8, 8)
     alusim = RegSim(16, 8)
+    memsim = MemSim(16, 16)
     vl = rtlil.convert(dut, ports=dut.ports())
     with open("test_scoreboard6600.il", "w") as f:
         f.write(vl)
-- 
2.30.2