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Add support for unpacked structs/unions
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Unpacked structs/unions may now be declared, and can contain members
with unpacked dimensions.

This is just syntactic sugar; unpacked structs/unions are handled
as if they were packed.

Note that arrays of structs/unions are still not supported.
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@daglem
daglem committed Mar 10, 2024
1 parent 9a54cfa commit eb4b6c6
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Showing 7 changed files with 257 additions and 108 deletions.
4 changes: 2 additions & 2 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -590,8 +590,8 @@ from SystemVerilog:
- enums are supported (including inside packages)
- but are currently not strongly typed

- packed structs and unions are supported
- arrays of packed structs/unions are currently not supported
- structs and unions are supported
- arrays of structs/unions are currently not supported
- structure literals are currently not supported

- multidimensional arrays are supported
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5 changes: 5 additions & 0 deletions frontends/ast/ast.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -212,6 +212,7 @@ AstNode::AstNode(AstNodeType type, AstNode *child1, AstNode *child2, AstNode *ch
is_reg = false;
is_logic = false;
is_signed = false;
is_unpacked = false;
is_string = false;
is_enum = false;
is_wand = false;
Expand Down Expand Up @@ -336,6 +337,8 @@ void AstNode::dumpAst(FILE *f, std::string indent) const
fprintf(f, " reg");
if (is_signed)
fprintf(f, " signed");
if (is_unpacked)
fprintf(f, " unpacked");
if (is_unsized)
fprintf(f, " unsized");
if (basic_prep)
Expand All @@ -359,6 +362,8 @@ void AstNode::dumpAst(FILE *f, std::string indent) const
std::swap(left, right);
fprintf(f, "[%d:%d]", left, right);
}
if (unpacked_dimensions)
fprintf(f, " unpacked_dimensions=%d", unpacked_dimensions);
}
if (is_enum) {
fprintf(f, " type=enum");
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2 changes: 1 addition & 1 deletion frontends/ast/ast.h
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Original file line number Diff line number Diff line change
Expand Up @@ -195,7 +195,7 @@ namespace AST
// node content - most of it is unused in most node types
std::string str;
std::vector<RTLIL::State> bits;
bool is_input, is_output, is_reg, is_logic, is_signed, is_string, is_wand, is_wor, range_valid, range_swapped, was_checked, is_unsized, is_custom_type;
bool is_input, is_output, is_reg, is_logic, is_signed, is_unpacked, is_string, is_wand, is_wor, range_valid, range_swapped, was_checked, is_unsized, is_custom_type;
int port_id, range_left, range_right;
uint32_t integer;
double realvalue;
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118 changes: 44 additions & 74 deletions frontends/ast/simplify.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -273,11 +273,6 @@ static int add_dimension(AstNode *node, AstNode *rnode)
return width;
}

[[noreturn]] static void struct_array_packing_error(AstNode *node)
{
node->input_error("Unpacked array in packed struct/union member %s\n", node->str.c_str());
}

static int size_packed_struct(AstNode *snode, int base_offset)
{
// Struct members will be laid out in the structure contiguously from left to right.
Expand All @@ -296,64 +291,20 @@ static int size_packed_struct(AstNode *snode, int base_offset)
}
else {
log_assert(node->type == AST_STRUCT_ITEM);
if (node->children.size() > 0 && node->children[0]->type == AST_RANGE) {
// member width e.g. bit [7:0] a
width = range_width(node, node->children[0]);
if (node->children.size() == 2) {
// Unpacked array. Note that this is a Yosys extension; only packed data types
// and integer data types are allowed in packed structs / unions in SystemVerilog.
if (node->children[1]->type == AST_RANGE) {
// Unpacked array, e.g. bit [63:0] a [0:3]
// Pretend it's declared as a packed array, e.g. bit [0:3][63:0] a
auto rnode = node->children[1];
if (rnode->children.size() == 1) {
// C-style array size, e.g. bit [63:0] a [4]
node->dimensions.push_back({ 0, rnode->range_left, true });
width *= rnode->range_left;
} else {
width *= add_dimension(node, rnode);
}
add_dimension(node, node->children[0]);
}
else {
// The Yosys extension for unpacked arrays in packed structs / unions
// only supports memories, i.e. e.g. logic [7:0] a [256] - see above.
struct_array_packing_error(node);
}
} else {
// Vector
add_dimension(node, node->children[0]);
}
// range nodes are now redundant
for (AstNode *child : node->children)
delete child;
node->children.clear();
}
else if (node->children.size() > 0 && node->children[0]->type == AST_MULTIRANGE) {
// Packed array, e.g. bit [3:0][63:0] a
if (node->children.size() != 1) {
// The Yosys extension for unpacked arrays in packed structs / unions
// only supports memories, i.e. e.g. logic [7:0] a [256] - see above.
struct_array_packing_error(node);
}
width = 1;
for (auto rnode : node->children[0]->children) {
width *= add_dimension(node, rnode);
}
// range nodes are now redundant
for (AstNode *child : node->children)
delete child;
node->children.clear();
}
else if (node->range_left < 0) {
// 1 bit signal: bit, logic or reg
width = 1;
node->dimensions.push_back({ 0, width, false });
}
else {
// already resolved and compacted
width = node->range_left - node->range_right + 1;
// Pretend it's just a wire in order to resolve the type.
node->type = AST_WIRE;
while (node->simplify(true, 1, -1, false)) { }
node->type = AST_STRUCT_ITEM;
width = 1;
for (int i = 0; i < GetSize(node->dimensions); i++) {
width *= node->dimensions[i].range_width;
}

// range nodes are now redundant
for (AstNode *child : node->children)
delete child;
node->children.clear();

if (is_union) {
node->range_right = base_offset;
node->range_left = base_offset + width - 1;
Expand All @@ -362,8 +313,10 @@ static int size_packed_struct(AstNode *snode, int base_offset)
node->range_right = base_offset + offset;
node->range_left = base_offset + offset + width - 1;
}

node->range_valid = true;
}

if (is_union) {
// check that all members have the same size
if (packed_width == -1) {
Expand Down Expand Up @@ -1425,6 +1378,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
did_something = true;
}
}

// determine member offsets and widths
size_packed_struct(this, 0);

Expand All @@ -1446,7 +1400,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin

// Pretend it's just a wire in order to resolve the type.
type = AST_WIRE;
while (is_custom_type && simplify(const_fold, stage, width_hint, sign_hint)) {};
while (is_custom_type && simplify(const_fold, stage, width_hint, sign_hint)) { }
if (type == AST_WIRE)
type = AST_STRUCT_ITEM;

Expand Down Expand Up @@ -1859,7 +1813,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
// Resolve the typedef from the bottom up, recursing within the current
// block of code. Defer further simplification until the complete type is
// resolved.
while (template_node->is_custom_type && template_node->simplify(const_fold, stage, width_hint, sign_hint)) {};
while (template_node->is_custom_type && template_node->simplify(const_fold, stage, width_hint, sign_hint)) { }

if (!str.empty() && str[0] == '\\' && (template_node->type == AST_STRUCT || template_node->type == AST_UNION)) {
// replace instance with wire representing the packed structure
Expand All @@ -1886,10 +1840,12 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
// if an enum then add attributes to support simulator tracing
newNode->annotateTypedEnums(template_node);

bool add_packed_dimensions = (type == AST_WIRE && GetSize(children) > 1) || (type == AST_MEMORY && GetSize(children) > 2);
bool unpacked_base_type = newNode->is_unpacked || newNode->type == AST_MEMORY;
bool add_unpacked_dimensions = is_unpacked || type == AST_MEMORY;
bool add_packed_dimensions = (!add_unpacked_dimensions && GetSize(children) > 1) || (add_unpacked_dimensions && GetSize(children) > 2);

// Cannot add packed dimensions if unpacked dimensions are already specified.
if (add_packed_dimensions && newNode->type == AST_MEMORY)
if (unpacked_base_type && add_packed_dimensions)
input_error("Cannot extend unpacked type `%s' with packed dimensions\n", type_name.c_str());

// Add packed dimensions.
Expand All @@ -1902,7 +1858,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
}

// Add unpacked dimensions.
if (type == AST_MEMORY) {
if (add_unpacked_dimensions) {
AstNode *unpacked = children.back();
if (GetSize(newNode->children) < 2)
newNode->children.push_back(unpacked->clone());
Expand Down Expand Up @@ -1930,7 +1886,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
type = AST_WIRE;
AstNode *expr = children[0];
children.erase(children.begin());
while (is_custom_type && simplify(const_fold, stage, width_hint, sign_hint)) {};
while (is_custom_type && simplify(const_fold, stage, width_hint, sign_hint)) { }
type = param_type;
children.insert(children.begin(), expr);

Expand Down Expand Up @@ -2043,22 +1999,23 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
if (!children.empty()) {
// Unpacked ranges first, then packed ranges.
for (int i = std::min(GetSize(children), 2) - 1; i >= 0; i--) {
int unpacked = i || children[i]->is_unpacked;
if (children[i]->type == AST_MULTIRANGE) {
int width = 1;
for (auto range : children[i]->children) {
width *= add_dimension(this, range);
if (i) unpacked_dimensions++;
if (unpacked) unpacked_dimensions++;
}
delete children[i];
int left = width - 1, right = 0;
if (i)
if (unpacked)
std::swap(left, right);
children[i] = new AstNode(AST_RANGE, mkconst_int(left, true), mkconst_int(right, true));
fixup_hierarchy_flags();
did_something = true;
} else if (children[i]->type == AST_RANGE) {
add_dimension(this, children[i]);
if (i) unpacked_dimensions++;
if (unpacked) unpacked_dimensions++;
}
}
} else {
Expand Down Expand Up @@ -2129,8 +2086,11 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin

if (found_sname) {
// structure member, rewrite this node to reference the packed struct wire
auto range = make_index_range(item_node);
newNode = new AstNode(AST_IDENTIFIER, range);
// Merge unpacked ranges with packed ranges.
int tmp_unpacked_dimensions = item_node->unpacked_dimensions;
item_node->unpacked_dimensions = 0;
newNode = new AstNode(AST_IDENTIFIER, make_index_range(item_node));
item_node->unpacked_dimensions = tmp_unpacked_dimensions;
newNode->str = sname;
// save type and original number of dimensions for $size() etc.
newNode->set_attribute(ID::wiretype, item_node->clone());
Expand All @@ -2148,6 +2108,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
}
}
}

// annotate identifiers using scope resolution and create auto-wires as needed
if (type == AST_IDENTIFIER) {
if (current_scope.count(str) == 0) {
Expand Down Expand Up @@ -2213,6 +2174,13 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
// Save original number of dimensions for $size() etc.
integer = dims_sel;

int tmp_unpacked_dimensions = id2ast->unpacked_dimensions;

if (id2ast->type != AST_MEMORY) {
// Merge unpacked ranges with packed ranges.
id2ast->unpacked_dimensions = 0;
}

// Split access into unpacked and packed parts.
AstNode *unpacked_range = nullptr;
AstNode *packed_range = nullptr;
Expand Down Expand Up @@ -2241,6 +2209,8 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
}
}

id2ast->unpacked_dimensions = tmp_unpacked_dimensions;

for (auto &it : children)
delete it;
children.clear();
Expand Down Expand Up @@ -2990,7 +2960,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
if (!children[0]->id2ast->range_valid)
goto skip_dynamic_range_lvalue_expansion;

AST::AstNode *member_node = children[0]->get_struct_member();
AstNode *member_node = children[0]->get_struct_member();
int wire_width = member_node ?
member_node->range_left - member_node->range_right + 1 :
children[0]->id2ast->range_left - children[0]->id2ast->range_right + 1;
Expand Down
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