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Accept (and ignore) SystemVerilog unique/priority if.

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Add support to the "read_verilog -sv" parser to validate the
"unique", "unique0", and "priority" keywords in contexts where
they're legal according to 1800-2012 12.4.2.

This affects only the grammar accepted; the behaviour of conditionals
is not changed.  (But accepting this syntax will provide scope for
possible optimisations as future work.)

Three test cases ("unique_if", "unique_if_else", and
"unique_if_else_begin") verify that the keywords are accepted where
legal and rejected where illegal, as described in the final paragraph
of 12.4.2.
This commit is contained in:
Gary Wong 2025-05-22 19:12:35 -06:00
parent 6c67b29bbb
commit 9770ece187
6 changed files with 66 additions and 2 deletions
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28
frontends/verilog/verilog_parser.y
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@ -426,7 +426,7 @@ static const AstNode *addAsgnBinopStmt(dict<IdString, AstNode*> *attr, AstNode *
%type <boolean> opt_property always_comb_or_latch always_or_always_ff
%type <boolean> opt_signedness_default_signed opt_signedness_default_unsigned
%type <integer> integer_atom_type integer_vector_type
%type <al> attr case_attr
%type <al> attr if_attr case_attr
%type <ast> struct_union
%type <ast_node_type> asgn_binop inc_or_dec_op
%type <ast> genvar_identifier
@ -2871,7 +2871,7 @@ behavioral_stmt:
ast_stack.pop_back();
ast_stack.pop_back();
} |
attr TOK_IF '(' expr ')' {
if_attr TOK_IF '(' expr ')' {
AstNode *node = new AstNode(AST_CASE);
AstNode *block = new AstNode(AST_BLOCK);
AstNode *cond = new AstNode(AST_COND, AstNode::mkconst_int(1, false, 1), block);
@ -2901,6 +2901,29 @@ behavioral_stmt:
ast_stack.pop_back();
};
if_attr:
attr {
$$ = $1;
} |
attr TOK_UNIQUE0 {
AstNode *context = ast_stack.back();
if( context && context->type == AST_BLOCK && context->get_bool_attribute(ID::promoted_if) )
frontend_verilog_yyerror("unique0 keyword cannot be used for 'else if' branch.");
$$ = $1; // accept unique0 keyword, but ignore it for now
} |
attr TOK_PRIORITY {
AstNode *context = ast_stack.back();
if( context && context->type == AST_BLOCK && context->get_bool_attribute(ID::promoted_if) )
frontend_verilog_yyerror("priority keyword cannot be used for 'else if' branch.");
$$ = $1; // accept priority keyword, but ignore it for now
} |
attr TOK_UNIQUE {
AstNode *context = ast_stack.back();
if( context && context->type == AST_BLOCK && context->get_bool_attribute(ID::promoted_if) )
frontend_verilog_yyerror("unique keyword cannot be used for 'else if' branch.");
$$ = $1; // accept unique keyword, but ignore it for now
};
case_attr:
attr {
$$ = $1;
@ -2948,6 +2971,7 @@ behavioral_stmt_list:
optional_else:
TOK_ELSE {
AstNode *block = new AstNode(AST_BLOCK);
block->attributes[ID::promoted_if] = AstNode::mkconst_int(1, false );
AstNode *cond = new AstNode(AST_COND, new AstNode(AST_DEFAULT), block);
SET_AST_NODE_LOC(cond, @1, @1);