From 04098933c724075cf350a79c3dc1f0dda6ec546b Mon Sep 17 00:00:00 2001
From: David Sawatzke <d-git@sawatzke.dev>
Date: Wed, 16 Apr 2025 13:26:50 +0200
Subject: [PATCH] cxxrtl: Add internal cell "bwmux"
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Mirrors the implementation for the smt2 backend

Co-authored-by: Martin Povišer <povik@cutebit.org>
---
 backends/cxxrtl/cxxrtl_backend.cc       | 10 +++++++++-
 backends/cxxrtl/runtime/cxxrtl/cxxrtl.h |  5 +++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/backends/cxxrtl/cxxrtl_backend.cc b/backends/cxxrtl/cxxrtl_backend.cc
index b9958c5fb..052699ad6 100644
--- a/backends/cxxrtl/cxxrtl_backend.cc
+++ b/backends/cxxrtl/cxxrtl_backend.cc
@@ -200,7 +200,7 @@ bool is_extending_cell(RTLIL::IdString type)
 bool is_inlinable_cell(RTLIL::IdString type)
 {
 	return is_unary_cell(type) || is_binary_cell(type) || type.in(
-		ID($mux), ID($concat), ID($slice), ID($pmux), ID($bmux), ID($demux));
+		ID($mux), ID($concat), ID($slice), ID($pmux), ID($bmux), ID($demux), ID($bwmux));
 }
 
 bool is_ff_cell(RTLIL::IdString type)
@@ -1198,6 +1198,14 @@ struct CxxrtlWorker {
 			f << ">(";
 			dump_sigspec_rhs(cell->getPort(ID::S), for_debug);
 			f << ").val()";
+		// Bitwise muxes
+		} else if (cell->type == ID($bwmux)) {
+			dump_sigspec_rhs(cell->getPort(ID::A), for_debug);
+			f << ".bwmux(";
+			dump_sigspec_rhs(cell->getPort(ID::B), for_debug);
+			f << ",";
+			dump_sigspec_rhs(cell->getPort(ID::S), for_debug);
+			f << ").val()";
 		// Demuxes
 		} else if (cell->type == ID($demux)) {
 			dump_sigspec_rhs(cell->getPort(ID::A), for_debug);
diff --git a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
index 9634b833b..37c84895f 100644
--- a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
+++ b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
@@ -498,6 +498,11 @@ struct value : public expr_base<value<Bits>> {
 		return result;
 	}
 
+	CXXRTL_ALWAYS_INLINE
+	value<Bits> bwmux(const value<Bits> &b, const value<Bits> &s) const {
+		return (bit_and(s.bit_not())).bit_or(b.bit_and(s));
+	}
+
 	template<size_t ResultBits, size_t SelBits>
 	value<ResultBits> demux(const value<SelBits> &sel) const {
 		static_assert(Bits << SelBits == ResultBits, "invalid sizes used in demux()");