random regression test shows an inter-dependency fail

diff --git a/src/experiment/score6600.py b/src/experiment/score6600.py
index 9e17b3f2a516e470b569b731b8937ac6e8b3bed5..455dfec5e9f3481558e2ebef12648e6770e29509 100644 (file)
--- a/src/experiment/score6600.py
+++ b/src/experiment/score6600.py
@@ -374,12 +374,11 @@ def scoreboard_sim(dut, alusim):
 
     instrs = []
     if False:
-        for i in range(2):
+        for i in range(50):
             src1 = randint(1, dut.n_regs-1)
             src2 = randint(1, dut.n_regs-1)
             while True:
                 dest = randint(1, dut.n_regs-1)
-                break
                 if dest not in [src1, src2]:
                     break
             #src1 = 2
@@ -387,19 +386,33 @@ def scoreboard_sim(dut, alusim):
             #dest = 2
 
             op = randint(0, 1)
-            op = i % 2
-            op = 0
-        instrs.append((src1, src2, dest, op))
+            #op = i % 2
+            #op = 0
+
+            instrs.append((src1, src2, dest, op))
 
     if False:
         instrs.append((2, 3, 3, 0))
         instrs.append((5, 3, 3, 1))
 
-    if True:
+    if False:
         instrs.append((5, 6, 2, 1))
         instrs.append((2, 2, 4, 0))
         #instrs.append((2, 2, 3, 1))
 
+    if False:
+        instrs.append((2, 1, 2, 0))
+
+    if False:
+        instrs.append((2, 6, 2, 1))
+        instrs.append((2, 1, 2, 0))
+
+    if True:
+        instrs.append((1, 4, 7, 1))
+        instrs.append((7, 1, 5, 0))
+        instrs.append((4, 3, 1, 1))
+        instrs.append((6, 5, 7, 1))
+
     for i, (src1, src2, dest, op) in enumerate(instrs):
 
         print ("instr %d: %d %d %d %d\n" % (i, op, src1, src2, dest))

diff --git a/src/scoreboard/dependence_cell.py b/src/scoreboard/dependence_cell.py
index 649b44e283c1976a78f5c32afdbd65329294462f..a45c5839785b05f0393080b7cf328b945abefa2a 100644 (file)
--- a/src/scoreboard/dependence_cell.py
+++ b/src/scoreboard/dependence_cell.py
@@ -122,8 +122,15 @@ class DependenceCell(Elaboratable):
                        (src2_c, self.src2_i)]:
             m.d.comb += c.reg_i.eq(reg)
 
+        # wark-wark: yes, writing to the same reg you are reading is *NOT*
+        # a write-after-read hazard.
+        selfhazard = Signal(reset_less=False)
+        m.d.comb += selfhazard.eq((self.dest_i & self.src1_i) |
+                                  (self.dest_i & self.src2_i))
+
         # connect up hazard checks: read-after-write and write-after-read
-        m.d.comb += dest_c.hazard_i.eq(self.rd_pend_i) # read-after-write
+        with m.If(~selfhazard):
+            m.d.comb += dest_c.hazard_i.eq(self.rd_pend_i) # read-after-write
         m.d.comb += src1_c.hazard_i.eq(self.wr_pend_i) # write-after-read
         m.d.comb += src2_c.hazard_i.eq(self.wr_pend_i) # write-after-read
 
@@ -137,7 +144,8 @@ class DependenceCell(Elaboratable):
         # to be accumulated to indicate if register is in use (globally)
         # after ORing, is fed back in to rd_pend_i / wr_pend_i
         m.d.comb += self.rd_rsel_o.eq(src1_c.q_o | src2_c.q_o)
-        m.d.comb += self.wr_rsel_o.eq(dest_c.q_o)
+        with m.If(~selfhazard):
+            m.d.comb += self.wr_rsel_o.eq(dest_c.q_o)
 
         return m