From 9cc04f05fff07d38c685614190007e107ee8b891 Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Wed, 3 Feb 2021 21:23:22 +0000
Subject: [PATCH] add SVP64PowerDecoder, extracts svp64 remap if correctly
 identified

---
 src/soc/decoder/power_decoder.py  |  1 +
 src/soc/decoder/power_decoder2.py | 51 +++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/src/soc/decoder/power_decoder.py b/src/soc/decoder/power_decoder.py
index bdad81ba..81a80b8b 100644
--- a/src/soc/decoder/power_decoder.py
+++ b/src/soc/decoder/power_decoder.py
@@ -493,6 +493,7 @@ class TopPowerDecoder(PowerDecoder):
     def elaborate(self, platform):
         m = PowerDecoder.elaborate(self, platform)
         comb = m.d.comb
+        # sigh duplicated in SVP64PowerDecoder
         # raw opcode in assumed to be in LE order: byte-reverse it to get BE
         raw_le = self.raw_opcode_in
         l = []
diff --git a/src/soc/decoder/power_decoder2.py b/src/soc/decoder/power_decoder2.py
index 72b0e246..2f6c0bde 100644
--- a/src/soc/decoder/power_decoder2.py
+++ b/src/soc/decoder/power_decoder2.py
@@ -1269,6 +1269,53 @@ class PowerDecode2(PowerDecodeSubset):
         comb += self.do_copy("cia", self.state.pc, True)  # copy of PC "state"
 
 
+# SVP64 Prefix fields: see https://libre-soc.org/openpower/sv/svp64/
+# identifies if an instruction is a SVP64-encoded prefix, and extracts
+# the 24-bit SVP64 context (RM) if it is
+class SVP64PowerDecoder(Elaboratable):
+
+    def __init__(self):
+        self.opcode_in = Signal(32, reset_less=True)
+        self.raw_opcode_in = Signal.like(self.opcode_in, reset_less=True)
+        self.is_svp64_mode = Signal(1, reset_less=True)
+        self.svp64_rm = Signal(24, reset_less=True)
+        self.bigendian = Signal(reset_less=True)
+
+    def elaborate(self, platform):
+        m = Module()
+        comb = m.d.comb
+        # sigh copied this from TopPowerDecoder
+        # raw opcode in assumed to be in LE order: byte-reverse it to get BE
+        raw_le = self.raw_opcode_in
+        l = []
+        for i in range(0, 32, 8):
+            l.append(raw_le[i:i+8])
+        l.reverse()
+        raw_be = Cat(*l)
+        comb += self.opcode_in.eq(Mux(self.bigendian, raw_be, raw_le))
+
+        # start identifying if the incoming opcode is SVP64 prefix)
+        major = Signal(6, reset_less=True)
+
+        comb += major.eq(self.opcode_in[26:32])
+        comb += self.is_svp64_mode.eq((major == Const(1, 6)) & # EXT01
+                                      self.opcode_in[31-7] & # identifier
+                                      self.opcode_in[31-9])  # bits
+
+        # now grab the 24-bit ReMap context bits,
+        rmfields = [6, 8] + list(range(10,32)) # SVP64 24-bit RM
+        l = []
+        for idx in rmfields:
+            l.append(self.opcode_in[32-idx])
+        with m.If(self.is_svp64_mode):
+            comb += self.svp64_rm.eq(Cat(*l))
+
+        return m
+
+    def ports(self):
+        return [self.opcode_in, self.raw_opcode_in, self.is_svp64_mode,
+                self.svp64_rm, self.bigendian]
+
 def get_rdflags(e, cu):
     rdl = []
     for idx in range(cu.n_src):
@@ -1280,6 +1327,10 @@ def get_rdflags(e, cu):
 
 
 if __name__ == '__main__':
+    svp64 = SVP64PowerDecoder()
+    vl = rtlil.convert(svp64, ports=svp64.ports())
+    with open("svp64_dec.il", "w") as f:
+        f.write(vl)
     pdecode = create_pdecode()
     dec2 = PowerDecode2(pdecode)
     vl = rtlil.convert(dec2, ports=dec2.ports() + pdecode.ports())
-- 
2.30.2