diff options
Diffstat (limited to 'backends/firrtl/firrtl.cc')
-rw-r--r-- | backends/firrtl/firrtl.cc | 296 |
1 files changed, 203 insertions, 93 deletions
diff --git a/backends/firrtl/firrtl.cc b/backends/firrtl/firrtl.cc index bb5ea2932..5be6d60fd 100644 --- a/backends/firrtl/firrtl.cc +++ b/backends/firrtl/firrtl.cc @@ -381,10 +381,10 @@ struct FirrtlWorker // Given an expression for a shift amount, and a maximum width, // generate the FIRRTL expression for equivalent dynamic shift taking into account FIRRTL shift semantics. - std::string gen_dshl(const string b_expr, const int b_padded_width) + std::string gen_dshl(const string b_expr, const int b_width) { string result = b_expr; - if (b_padded_width >= FIRRTL_MAX_DSH_WIDTH_ERROR) { + if (b_width >= FIRRTL_MAX_DSH_WIDTH_ERROR) { int max_shift_width_bits = FIRRTL_MAX_DSH_WIDTH_ERROR - 1; string max_shift_string = stringf("UInt<%d>(%d)", max_shift_width_bits, (1<<max_shift_width_bits) - 1); // Deal with the difference in semantics between FIRRTL and verilog @@ -422,22 +422,33 @@ struct FirrtlWorker for (auto cell : module->cells()) { - bool extract_y_bits = false; // Assume no extraction of final bits will be required. + static Const ndef(0, 0); + // Is this cell is a module instance? if (cell->type[0] != '$') { process_instance(cell, wire_exprs); continue; } + // Not a module instance. Set up cell properties + bool extract_y_bits = false; // Assume no extraction of final bits will be required. + int a_width = cell->parameters.at("\\A_WIDTH", ndef).as_int(); // The width of "A" + int b_width = cell->parameters.at("\\B_WIDTH", ndef).as_int(); // The width of "A" + const int y_width = cell->parameters.at("\\Y_WIDTH", ndef).as_int(); // The width of the result + const bool a_signed = cell->parameters.at("\\A_SIGNED", ndef).as_bool(); + const bool b_signed = cell->parameters.at("\\B_SIGNED", ndef).as_bool(); + bool firrtl_is_signed = a_signed; // The result is signed (subsequent code may change this). + int firrtl_width = 0; + string primop; + bool always_uint = false; + string y_id = make_id(cell->name); + if (cell->type.in("$not", "$logic_not", "$neg", "$reduce_and", "$reduce_or", "$reduce_xor", "$reduce_bool", "$reduce_xnor")) { - string y_id = make_id(cell->name); - bool is_signed = cell->parameters.at("\\A_SIGNED").as_bool(); - int y_width = cell->parameters.at("\\Y_WIDTH").as_int(); string a_expr = make_expr(cell->getPort("\\A")); wire_decls.push_back(stringf(" wire %s: UInt<%d>\n", y_id.c_str(), y_width)); - if (cell->parameters.at("\\A_SIGNED").as_bool()) { + if (a_signed) { a_expr = "asSInt(" + a_expr + ")"; } @@ -446,12 +457,13 @@ struct FirrtlWorker a_expr = stringf("pad(%s, %d)", a_expr.c_str(), y_width); } - string primop; - bool always_uint = false; + // Assume the FIRRTL width is a single bit. + firrtl_width = 1; if (cell->type == "$not") primop = "not"; else if (cell->type == "$neg") { primop = "neg"; - is_signed = true; // Result of "neg" is signed (an SInt). + firrtl_is_signed = true; // Result of "neg" is signed (an SInt). + firrtl_width = a_width; } else if (cell->type == "$logic_not") { primop = "eq"; a_expr = stringf("%s, UInt(0)", a_expr.c_str()); @@ -466,14 +478,12 @@ struct FirrtlWorker else if (cell->type == "$reduce_bool") { primop = "neq"; // Use the sign of the a_expr and its width as the type (UInt/SInt) and width of the comparand. - bool a_signed = cell->parameters.at("\\A_SIGNED").as_bool(); - int a_width = cell->parameters.at("\\A_WIDTH").as_int(); a_expr = stringf("%s, %cInt<%d>(0)", a_expr.c_str(), a_signed ? 'S' : 'U', a_width); } string expr = stringf("%s(%s)", primop.c_str(), a_expr.c_str()); - if ((is_signed && !always_uint)) + if ((firrtl_is_signed && !always_uint)) expr = stringf("asUInt(%s)", expr.c_str()); cell_exprs.push_back(stringf(" %s <= %s\n", y_id.c_str(), expr.c_str())); @@ -481,81 +491,121 @@ struct FirrtlWorker continue; } - if (cell->type.in("$add", "$sub", "$mul", "$div", "$mod", "$xor", "$and", "$or", "$eq", "$eqx", + if (cell->type.in("$add", "$sub", "$mul", "$div", "$mod", "$xor", "$xnor", "$and", "$or", "$eq", "$eqx", "$gt", "$ge", "$lt", "$le", "$ne", "$nex", "$shr", "$sshr", "$sshl", "$shl", - "$logic_and", "$logic_or")) + "$logic_and", "$logic_or", "$pow")) { - string y_id = make_id(cell->name); - bool is_signed = cell->parameters.at("\\A_SIGNED").as_bool(); - int y_width = cell->parameters.at("\\Y_WIDTH").as_int(); string a_expr = make_expr(cell->getPort("\\A")); string b_expr = make_expr(cell->getPort("\\B")); - int b_padded_width = cell->parameters.at("\\B_WIDTH").as_int(); wire_decls.push_back(stringf(" wire %s: UInt<%d>\n", y_id.c_str(), y_width)); - if (cell->parameters.at("\\A_SIGNED").as_bool()) { + if (a_signed) { a_expr = "asSInt(" + a_expr + ")"; - } - // Shift amount is always unsigned, and needn't be padded to result width. - if (!cell->type.in("$shr", "$sshr", "$shl", "$sshl")) { - if (cell->parameters.at("\\B_SIGNED").as_bool()) { - b_expr = "asSInt(" + b_expr + ")"; + // Expand the "A" operand to the result width + if (a_width < y_width) { + a_expr = stringf("pad(%s, %d)", a_expr.c_str(), y_width); + a_width = y_width; } - if (b_padded_width < y_width) { - auto b_sig = cell->getPort("\\B"); - b_padded_width = y_width; + } + // Shift amount is always unsigned, and needn't be padded to result width, + // otherwise, we need to cast the b_expr appropriately + if (b_signed && !cell->type.in("$shr", "$sshr", "$shl", "$sshl", "$pow")) { + b_expr = "asSInt(" + b_expr + ")"; + // Expand the "B" operand to the result width + if (b_width < y_width) { + b_expr = stringf("pad(%s, %d)", b_expr.c_str(), y_width); + b_width = y_width; } } + // For the arithmetic ops, expand operand widths to result widths befor performing the operation. + // This corresponds (according to iverilog) to what verilog compilers implement. + if (cell->type.in("$add", "$sub", "$mul", "$div", "$mod", "$xor", "$xnor", "$and", "$or")) + { + if (a_width < y_width) { + a_expr = stringf("pad(%s, %d)", a_expr.c_str(), y_width); + a_width = y_width; + } + if (b_width < y_width) { + b_expr = stringf("pad(%s, %d)", b_expr.c_str(), y_width); + b_width = y_width; + } + } + // Assume the FIRRTL width is the width of "A" + firrtl_width = a_width; auto a_sig = cell->getPort("\\A"); - if (cell->parameters.at("\\A_SIGNED").as_bool() & (cell->type == "$shr")) { - a_expr = "asUInt(" + a_expr + ")"; + if (cell->type == "$add") { + primop = "add"; + firrtl_is_signed = a_signed | b_signed; + firrtl_width = max(a_width, b_width); + } else if (cell->type == "$sub") { + primop = "sub"; + firrtl_is_signed = true; + int a_widthInc = (!a_signed && b_signed) ? 2 : (a_signed && !b_signed) ? 1 : 0; + int b_widthInc = (a_signed && !b_signed) ? 2 : (!a_signed && b_signed) ? 1 : 0; + firrtl_width = max(a_width + a_widthInc, b_width + b_widthInc); + } else if (cell->type == "$mul") { + primop = "mul"; + firrtl_is_signed = a_signed | b_signed; + firrtl_width = a_width + b_width; + } else if (cell->type == "$div") { + primop = "div"; + firrtl_is_signed = a_signed | b_signed; + firrtl_width = a_width; + } else if (cell->type == "$mod") { + primop = "rem"; + firrtl_width = min(a_width, b_width); + } else if (cell->type == "$and") { + primop = "and"; + always_uint = true; + firrtl_width = max(a_width, b_width); } - - string primop; - bool always_uint = false; - if (cell->type == "$add") primop = "add"; - else if (cell->type == "$sub") primop = "sub"; - else if (cell->type == "$mul") primop = "mul"; - else if (cell->type == "$div") primop = "div"; - else if (cell->type == "$mod") primop = "rem"; - else if (cell->type == "$and") { - primop = "and"; - always_uint = true; - } else if (cell->type == "$or" ) { - primop = "or"; - always_uint = true; - } + primop = "or"; + always_uint = true; + firrtl_width = max(a_width, b_width); + } else if (cell->type == "$xor") { - primop = "xor"; - always_uint = true; - } + primop = "xor"; + always_uint = true; + firrtl_width = max(a_width, b_width); + } + else if (cell->type == "$xnor") { + primop = "xnor"; + always_uint = true; + firrtl_width = max(a_width, b_width); + } else if ((cell->type == "$eq") | (cell->type == "$eqx")) { - primop = "eq"; - always_uint = true; - } + primop = "eq"; + always_uint = true; + firrtl_width = 1; + } else if ((cell->type == "$ne") | (cell->type == "$nex")) { - primop = "neq"; - always_uint = true; - } + primop = "neq"; + always_uint = true; + firrtl_width = 1; + } else if (cell->type == "$gt") { - primop = "gt"; - always_uint = true; - } + primop = "gt"; + always_uint = true; + firrtl_width = 1; + } else if (cell->type == "$ge") { - primop = "geq"; - always_uint = true; - } + primop = "geq"; + always_uint = true; + firrtl_width = 1; + } else if (cell->type == "$lt") { - primop = "lt"; - always_uint = true; - } + primop = "lt"; + always_uint = true; + firrtl_width = 1; + } else if (cell->type == "$le") { - primop = "leq"; - always_uint = true; - } + primop = "leq"; + always_uint = true; + firrtl_width = 1; + } else if ((cell->type == "$shl") | (cell->type == "$sshl")) { // FIRRTL will widen the result (y) by the amount of the shift. // We'll need to offset this by extracting the un-widened portion as Verilog would do. @@ -564,11 +614,14 @@ struct FirrtlWorker auto b_sig = cell->getPort("\\B"); if (b_sig.is_fully_const()) { primop = "shl"; - b_expr = std::to_string(b_sig.as_int()); + int shift_amount = b_sig.as_int(); + b_expr = std::to_string(shift_amount); + firrtl_width = a_width + shift_amount; } else { primop = "dshl"; // Convert from FIRRTL left shift semantics. - b_expr = gen_dshl(b_expr, b_padded_width); + b_expr = gen_dshl(b_expr, b_width); + firrtl_width = a_width + (1 << b_width) - 1; } } else if ((cell->type == "$shr") | (cell->type == "$sshr")) { @@ -578,36 +631,86 @@ struct FirrtlWorker auto b_sig = cell->getPort("\\B"); if (b_sig.is_fully_const()) { primop = "shr"; - b_expr = std::to_string(b_sig.as_int()); + int shift_amount = b_sig.as_int(); + b_expr = std::to_string(shift_amount); + firrtl_width = max(1, a_width - shift_amount); } else { primop = "dshr"; + firrtl_width = a_width; + } + // We'll need to do some special fixups if the source (and thus result) is signed. + if (firrtl_is_signed) { + // If this is a "logical" shift right, pretend the source is unsigned. + if (cell->type == "$shr") { + a_expr = "asUInt(" + a_expr + ")"; + } } } else if ((cell->type == "$logic_and")) { - primop = "and"; - a_expr = "neq(" + a_expr + ", UInt(0))"; - b_expr = "neq(" + b_expr + ", UInt(0))"; - always_uint = true; - } + primop = "and"; + a_expr = "neq(" + a_expr + ", UInt(0))"; + b_expr = "neq(" + b_expr + ", UInt(0))"; + always_uint = true; + firrtl_width = 1; + } else if ((cell->type == "$logic_or")) { - primop = "or"; - a_expr = "neq(" + a_expr + ", UInt(0))"; - b_expr = "neq(" + b_expr + ", UInt(0))"; - always_uint = true; - } + primop = "or"; + a_expr = "neq(" + a_expr + ", UInt(0))"; + b_expr = "neq(" + b_expr + ", UInt(0))"; + always_uint = true; + firrtl_width = 1; + } + else if ((cell->type == "$pow")) { + if (a_sig.is_fully_const() && a_sig.as_int() == 2) { + // We'll convert this to a shift. To simplify things, change the a_expr to "1" + // so we can use b_expr directly as a shift amount. + // Only support 2 ** N (i.e., shift left) + // FIRRTL will widen the result (y) by the amount of the shift. + // We'll need to offset this by extracting the un-widened portion as Verilog would do. + a_expr = firrtl_is_signed ? "SInt(1)" : "UInt(1)"; + extract_y_bits = true; + // Is the shift amount constant? + auto b_sig = cell->getPort("\\B"); + if (b_sig.is_fully_const()) { + primop = "shl"; + int shiftAmount = b_sig.as_int(); + if (shiftAmount < 0) { + log_error("Negative power exponent - %d: %s.%s\n", shiftAmount, log_id(module), log_id(cell)); + } + b_expr = std::to_string(shiftAmount); + firrtl_width = a_width + shiftAmount; + } else { + primop = "dshl"; + // Convert from FIRRTL left shift semantics. + b_expr = gen_dshl(b_expr, b_width); + firrtl_width = a_width + (1 << b_width) - 1; + } + } else { + log_error("Non power 2: %s.%s\n", log_id(module), log_id(cell)); + } + } if (!cell->parameters.at("\\B_SIGNED").as_bool()) { b_expr = "asUInt(" + b_expr + ")"; } - string expr = stringf("%s(%s, %s)", primop.c_str(), a_expr.c_str(), b_expr.c_str()); + string expr; + // Deal with $xnor == ~^ (not xor) + if (primop == "xnor") { + expr = stringf("not(xor(%s, %s))", a_expr.c_str(), b_expr.c_str()); + } else { + expr = stringf("%s(%s, %s)", primop.c_str(), a_expr.c_str(), b_expr.c_str()); + } - // Deal with FIRRTL's "shift widens" semantics + // Deal with FIRRTL's "shift widens" semantics, or the need to widen the FIRRTL result. + // If the operation is signed, the FIRRTL width will be 1 one bit larger. if (extract_y_bits) { expr = stringf("bits(%s, %d, 0)", expr.c_str(), y_width - 1); + } else if (firrtl_is_signed && (firrtl_width + 1) < y_width) { + expr = stringf("pad(%s, %d)", expr.c_str(), y_width); } - if ((is_signed && !always_uint) || cell->type.in("$sub")) + if ((firrtl_is_signed && !always_uint)) expr = stringf("asUInt(%s)", expr.c_str()); cell_exprs.push_back(stringf(" %s <= %s\n", y_id.c_str(), expr.c_str())); @@ -618,7 +721,6 @@ struct FirrtlWorker if (cell->type.in("$mux")) { - string y_id = make_id(cell->name); int width = cell->parameters.at("\\WIDTH").as_int(); string a_expr = make_expr(cell->getPort("\\A")); string b_expr = make_expr(cell->getPort("\\B")); @@ -762,15 +864,14 @@ struct FirrtlWorker if (clkpol == false) log_error("Negative edge clock on FF %s.%s.\n", log_id(module), log_id(cell)); - string q_id = make_id(cell->name); int width = cell->parameters.at("\\WIDTH").as_int(); string expr = make_expr(cell->getPort("\\D")); string clk_expr = "asClock(" + make_expr(cell->getPort("\\CLK")) + ")"; - wire_decls.push_back(stringf(" reg %s: UInt<%d>, %s\n", q_id.c_str(), width, clk_expr.c_str())); + wire_decls.push_back(stringf(" reg %s: UInt<%d>, %s\n", y_id.c_str(), width, clk_expr.c_str())); - cell_exprs.push_back(stringf(" %s <= %s\n", q_id.c_str(), expr.c_str())); - register_reverse_wire_map(q_id, cell->getPort("\\Q")); + cell_exprs.push_back(stringf(" %s <= %s\n", y_id.c_str(), expr.c_str())); + register_reverse_wire_map(y_id, cell->getPort("\\Q")); continue; } @@ -785,8 +886,6 @@ struct FirrtlWorker // assign y = a[b +: y_width]; // We'll extract the correct bits as part of the primop. - string y_id = make_id(cell->name); - int y_width = cell->parameters.at("\\Y_WIDTH").as_int(); string a_expr = make_expr(cell->getPort("\\A")); // Get the initial bit selector string b_expr = make_expr(cell->getPort("\\B")); @@ -808,18 +907,15 @@ struct FirrtlWorker // assign y = a >> b; // where b may be negative - string y_id = make_id(cell->name); - int y_width = cell->parameters.at("\\Y_WIDTH").as_int(); string a_expr = make_expr(cell->getPort("\\A")); string b_expr = make_expr(cell->getPort("\\B")); auto b_string = b_expr.c_str(); - int b_padded_width = cell->parameters.at("\\B_WIDTH").as_int(); string expr; wire_decls.push_back(stringf(" wire %s: UInt<%d>\n", y_id.c_str(), y_width)); if (cell->getParam("\\B_SIGNED").as_bool()) { // We generate a left or right shift based on the sign of b. - std::string dshl = stringf("bits(dshl(%s, %s), 0, %d)", a_expr.c_str(), gen_dshl(b_expr, b_padded_width).c_str(), y_width); + std::string dshl = stringf("bits(dshl(%s, %s), 0, %d)", a_expr.c_str(), gen_dshl(b_expr, b_width).c_str(), y_width); std::string dshr = stringf("dshr(%s, %s)", a_expr.c_str(), b_string); expr = stringf("mux(%s < 0, %s, %s)", b_string, @@ -833,6 +929,20 @@ struct FirrtlWorker register_reverse_wire_map(y_id, cell->getPort("\\Y")); continue; } + if (cell->type == "$pos") { + // assign y = a; +// printCell(cell); + string a_expr = make_expr(cell->getPort("\\A")); + // Verilog appears to treat the result as signed, so if the result is wider than "A", + // we need to pad. + if (a_width < y_width) { + a_expr = stringf("pad(%s, %d)", a_expr.c_str(), y_width); + } + wire_decls.push_back(stringf(" wire %s: UInt<%d>\n", y_id.c_str(), y_width)); + cell_exprs.push_back(stringf(" %s <= %s\n", y_id.c_str(), a_expr.c_str())); + register_reverse_wire_map(y_id, cell->getPort("\\Y")); + continue; + } log_warning("Cell type not supported: %s (%s.%s)\n", log_id(cell->type), log_id(module), log_id(cell)); } |