From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Thu, 27 Aug 2020 16:23:01 +0000 (+0100)
Subject: incompatibility with POWER9 on mulhw/u due to lack of spec clarity
X-Git-Tag: semi_working_ecp5~250^2~5
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=8f178b3d3cb5d8a923a6454eab59727fdd732a27;p=soc.git

incompatibility with POWER9 on mulhw/u due to lack of spec clarity
both microwatt and IBM POWER9 violate spec
http://lists.libre-soc.org/pipermail/libre-soc-dev/2020-August/000302.html
---

diff --git a/src/soc/decoder/power_decoder2.py b/src/soc/decoder/power_decoder2.py
index 046b715b..0629217e 100644
--- a/src/soc/decoder/power_decoder2.py
+++ b/src/soc/decoder/power_decoder2.py
@@ -451,7 +451,9 @@ class DecodeOE(Elaboratable):
 
             # mulhw, mulhwu, mulhd, mulhdu - these *ignore* OE
             # also rotate
-            with m.Case(MicrOp.OP_MUL_H64, MicrOp.OP_MUL_H32,
+            # XXX ARGH! ignoring OE causes incompatibility with microwatt
+            # http://lists.libre-soc.org/pipermail/libre-soc-dev/2020-August/000302.html
+            with m.Case(#MicrOp.OP_MUL_H64, MicrOp.OP_MUL_H32,
                         MicrOp.OP_SHL, MicrOp.OP_SHR, MicrOp.OP_RLC,
                         MicrOp.OP_RLCL, MicrOp.OP_RLCR,
                         MicrOp.OP_EXTSWSLI):