sv: fix always_comb auto nosync for nested and function blocks

[yosys.git] / frontends / ast / simplify.cc

diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 565025d3a063d710f851b021f4cbcddf2086b487..bd3e09c4b9cc09633d3193bf38f348b38a93303e 100644 (file)
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -744,6 +744,16 @@ static void mark_auto_nosync(AstNode *block, const AstNode *wire)
                        false);
 }
 
+// block names can be prefixed with an explicit scope during elaboration
+static bool is_autonamed_block(const std::string &str) {
+       size_t last_dot = str.rfind('.');
+       // unprefixed names: autonamed if the first char is a dollar sign
+       if (last_dot == std::string::npos)
+               return str.at(0) == '$'; // e.g., `$fordecl_block$1`
+       // prefixed names: autonamed if the final chunk begins with a dollar sign
+       return str.rfind(".$") == last_dot; // e.g., `\foo.bar.$fordecl_block$1`
+}
+
 // check a procedural block for auto-nosync markings, remove them, and add
 // nosync to local variables as necessary
 static void check_auto_nosync(AstNode *node)
@@ -2355,7 +2365,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 
                // if this is an autonamed block is in an always_comb
                if (current_always && current_always->attributes.count(ID::always_comb)
-                               && str.at(0) == '$')
+                               && is_autonamed_block(str))
                        // track local variables in this block so we can consider adding
                        // nosync once the block has been fully elaborated
                        for (AstNode *child : children)