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Merge pull request #1240 from ucb-bar/firrtl-properties+pow+xnor 

Support explicit FIRRTL properties for better accommodation of FIRRTL/Verilog semantic differences.
This commit is contained in:
Clifford Wolf 2019-08-07 12:31:32 +02:00 committed by GitHub
parent 4c49ddf36a 3b8c917025
commit 48f7682e32
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 209 additions and 97 deletions
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302
backends/firrtl/firrtl.cc
View File

@ -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());
// Deal with FIRRTL's "shift widens" semantics
if (extract_y_bits) {
expr = stringf("bits(%s, %d, 0)", expr.c_str(), y_width - 1);
string expr;
// Deal with $xnor == ~^ (not xor)
if (primop == "xnor") {
expr = stringf("not(xor(%s, %s))", a_expr.c_str(), b_expr.c_str());
} else {
expr = stringf("%s(%s, %s)", primop.c_str(), a_expr.c_str(), b_expr.c_str());
}
if ((is_signed && !always_uint) || cell->type.in("$sub"))
// 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 ((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));
}

4
tests/simple/xfirrtl
View File

@ -1,10 +1,12 @@
# This file contains the names of verilog files to exclude from verilog to FIRRTL regression tests due to known failures.
arraycells.v inst id[0] of
defvalue.sv Initial value not supported
dff_different_styles.v
dff_init.v Initial value not supported
generate.v combinational loop
hierdefparam.v inst id[0] of
i2c_master_tests.v $adff
implicit_ports.v not fully initialized
macros.v drops modules
mem2reg.v drops modules
mem_arst.v $adff
@ -12,7 +14,6 @@ memory.v $adff
multiplier.v inst id[0] of
muxtree.v drops modules
omsp_dbg_uart.v $adff
operators.v $pow
partsel.v drops modules
process.v drops modules
realexpr.v drops modules
@ -23,5 +24,6 @@ specify.v no code (empty module generates error
subbytes.v $adff
task_func.v drops modules
values.v combinational loop
wandwor.v Invalid connect to an expression that is not a reference or a WritePort.
vloghammer.v combinational loop
wreduce.v original verilog issues ( -x where x isn't declared signed)