From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sun, 7 Nov 2021 12:29:53 +0000 (+0000)
Subject: remove some of the uses of wrmask (redundant)
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=959a7d4ff9641229a3c96133164dfef0f3abf9e1;p=soc.git

remove some of the uses of wrmask (redundant)
https://bugs.libre-soc.org/show_bug.cgi?id=742

in MultiCompUnit, wrmask is the amalgamation of the incoming "data ok"
signals from an ALU.  ALUs are given the *option* to write to registers:
they are not told, "you absolutely have to write to this register"
but of course for Hazard purposes, the MultiCompUnit has to be told
to "hold" off the write until such time as the ALU can determine whether
it has anything to write

it _should_ now be possible for the ReservationStation version of
FunctionUnit to use combinatorial-setting of write data+ok
---

diff --git a/src/soc/experiment/compalu_multi.py b/src/soc/experiment/compalu_multi.py
index 101f86cd..55655a74 100644
--- a/src/soc/experiment/compalu_multi.py
+++ b/src/soc/experiment/compalu_multi.py
@@ -215,11 +215,9 @@ class MultiCompUnit(RegSpecALUAPI, Elaboratable):
         # is enough, when combined with when read-phase is done (rst_l.q)
         wr_any = Signal(reset_less=True)
         req_done = Signal(reset_less=True)
-        m.d.comb += self.done_o.eq(self.busy_o &
-                                   ~((self.wr.rel_o & ~self.wrmask).bool()))
+        m.d.comb += self.done_o.eq(self.busy_o & ~(self.wr.rel_o).bool())
         m.d.comb += wr_any.eq(self.wr.go_i.bool() | prev_wr_go.bool())
-        m.d.comb += req_done.eq(wr_any & ~self.alu.n.i_ready &
-                                ((req_l.q & self.wrmask) == 0))
+        m.d.comb += req_done.eq(wr_any & ~self.alu.n.i_ready & (req_l.q == 0))
         # argh, complicated hack: if there are no regs to write,
         # instead of waiting for regs that are never going to happen,
         # we indicate "done" when the ALU is "done"
@@ -360,7 +358,7 @@ class MultiCompUnit(RegSpecALUAPI, Elaboratable):
 
         # write-release gated by busy and by shadow (and write-mask)
         brd = Repl(self.busy_o & self.shadown_i, self.n_dst)
-        m.d.comb += self.wr.rel_o.eq(req_l.q & brd & self.wrmask)
+        m.d.comb += self.wr.rel_o.eq(req_l.q & brd)
 
         # output the data from the latch on go_write
         for i in range(self.n_dst):