From b019db1f373e6bfe2b55363d28b9b6828a1cca6c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcelina=20Ko=C5=9Bcielnicka?= <mwk@0x04.net>
Date: Wed, 26 May 2021 03:07:51 +0200
Subject: [PATCH] kernel/mem: Add helpers for write port widening.
---
kernel/mem.cc | 46 ++++++++++++++++++++++++++++++++++++++++++++++
kernel/mem.h | 11 +++++++++++
2 files changed, 57 insertions(+)
diff --git a/kernel/mem.cc b/kernel/mem.cc
index a7ee1f2d6..021e1991e 100644
--- a/kernel/mem.cc
+++ b/kernel/mem.cc
@@ -798,3 +798,49 @@ void Mem::prepare_wr_merge(int idx1, int idx2) {
oport.priority_mask[idx1] = true;
}
}
+
+void Mem::widen_prep(int wide_log2) {
+ // Make sure start_offset and size are aligned to the port width,
+ // adjust if necessary.
+ int mask = ((1 << wide_log2) - 1);
+ int delta = start_offset & mask;
+ start_offset -= delta;
+ size += delta;
+ if (size & mask) {
+ size |= mask;
+ size++;
+ }
+}
+
+void Mem::widen_wr_port(int idx, int wide_log2) {
+ widen_prep(wide_log2);
+ auto &port = wr_ports[idx];
+ log_assert(port.wide_log2 <= wide_log2);
+ if (port.wide_log2 < wide_log2) {
+ SigSpec new_data, new_en;
+ SigSpec addr_lo = port.addr.extract(0, wide_log2);
+ for (int sub = 0; sub < (1 << wide_log2); sub += (1 << port.wide_log2))
+ {
+ Const cur_addr_lo(sub, wide_log2);
+ if (addr_lo == cur_addr_lo) {
+ // Always writes to this subword.
+ new_data.append(port.data);
+ new_en.append(port.en);
+ } else if (addr_lo.is_fully_const()) {
+ // Never writes to this subword.
+ new_data.append(Const(State::Sx, GetSize(port.data)));
+ new_en.append(Const(State::S0, GetSize(port.data)));
+ } else {
+ // May or may not write to this subword.
+ new_data.append(port.data);
+ SigSpec addr_eq = module->Eq(NEW_ID, addr_lo, cur_addr_lo);
+ SigSpec en = module->Mux(NEW_ID, Const(State::S0, GetSize(port.data)), port.en, addr_eq);
+ new_en.append(en);
+ }
+ }
+ port.addr.replace(port.wide_log2, Const(State::S0, wide_log2 - port.wide_log2));
+ port.data = new_data;
+ port.en = new_en;
+ port.wide_log2 = wide_log2;
+ }
+}
diff --git a/kernel/mem.h b/kernel/mem.h
index 82eb0f488..b4a9cb695 100644
--- a/kernel/mem.h
+++ b/kernel/mem.h
@@ -109,6 +109,17 @@ struct Mem {
// is called.
void prepare_wr_merge(int idx1, int idx2);
+ // Prepares the memory for widening a port to a given width. This
+ // involves ensuring that start_offset and size are aligned to the
+ // target width.
+ void widen_prep(int wide_log2);
+
+ // Widens a write port up to a given width. The newly port is
+ // equivalent to the original, made by replicating enable/data bits
+ // and masking enable bits with decoders on the low part of the
+ // original address.
+ void widen_wr_port(int idx, int wide_log2);
+
Mem(Module *module, IdString memid, int width, int start_offset, int size) : module(module), memid(memid), packed(false), mem(nullptr), cell(nullptr), width(width), start_offset(start_offset), size(size) {}
};