[otbn] Wrap bn.movr increments modulo 32
This is what the RTL did already. Make the spec match the equivalent
documentation for bn.lid and update the ISS to match.
Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>
diff --git a/hw/ip/otbn/data/bignum-insns.yml b/hw/ip/otbn/data/bignum-insns.yml
index 65a690f..1fdef5d 100644
--- a/hw/ip/otbn/data/bignum-insns.yml
+++ b/hw/ip/otbn/data/bignum-insns.yml
@@ -984,7 +984,12 @@
<grd>[<grd_inc>], <grs>[<grs_inc>]
doc: |
Copies WDR contents between registers with indirect addressing.
- Optionally, either the source or the destination register address can be incremented by 1.
+
+ After the operation, either the value in the GPR `grd`, or the value in `grs` can be optionally incremented.
+
+ - If `grd_inc` is set, `grd` is updated to be `(*grd + 1) & 0x1f`.
+ - If `grs_inc` is set, `grs` is updated to be `(*grs + 1) & 0x1f`.
+
decode: |
s = UInt(grs)
d = UInt(grd)
diff --git a/hw/ip/otbn/dv/otbnsim/sim/insn.py b/hw/ip/otbn/dv/otbnsim/sim/insn.py
index 306cb7a..a125c7a 100644
--- a/hw/ip/otbn/dv/otbnsim/sim/insn.py
+++ b/hw/ip/otbn/dv/otbnsim/sim/insn.py
@@ -886,11 +886,11 @@
state.wdrs.get_reg(wrd).write_unsigned(value)
if self.grd_inc:
- new_grd_val = (grd_val + 1) & ((1 << 32) - 1)
+ new_grd_val = (grd_val + 1) & 0x1f
state.gprs.get_reg(self.grd).write_unsigned(new_grd_val)
if self.grs_inc:
- new_grs_val = (grs_val + 1) & ((1 << 32) - 1)
+ new_grs_val = (grs_val + 1) & 0x1f
state.gprs.get_reg(self.grs).write_unsigned(new_grs_val)
