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ast/simplify: Make in_lvalue/in_param into props of AST nodes

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Instead of passing around in_lvalue/in_param flags to simplify, we make
the flags into properties of the AST nodes themselves. After the tree
is first parsed, we once do

  ast->fixup_hierarchy_flags(true)

to walk the full hierarchy and set the flags to their initial correct
values. Then as long as one is using ->clone(), ->cloneInto() and the
AstNode constructor (with children passed to it) to modify the tree, the
flags will be kept in sync automatically. On the other hand if we are
modifying the children list of an existing node, we may need to call

  node->fixup_hierarchy_flags()

to do a localized fixup. That fixup will update the flags on the node's
children, and will propagate the change down the tree if necessary.

clone() doesn't always retain the flags of the subtree being cloned. It
will produce a tree with a consistent setting of the flags, but the
root doesn't have in_param/in_lvalue set unless it's intrinsic to the
type of node being cloned (e.g. AST_PARAMETER). cloneInto() will make
sure the cloned subtree has the flags consistent with the new placement
in a hierarchy.

Add asserts to make sure the old and new way of determining the flags
agree.
This commit is contained in:
Martin Povišer 2023-04-05 11:00:07 +02:00
parent 10d0e69588
commit 22b99413e8
4 changed files with 222 additions and 42 deletions
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25
frontends/ast/ast.h
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@ -221,6 +221,13 @@ namespace AST
std::string filename;
AstSrcLocType location;
// are we embedded in an lvalue, param?
// (see fixup_hierarchy_flags)
bool in_lvalue;
bool in_param;
bool in_lvalue_from_above;
bool in_param_from_above;
// creating and deleting nodes
AstNode(AstNodeType type = AST_NONE, AstNode *child1 = nullptr, AstNode *child2 = nullptr, AstNode *child3 = nullptr, AstNode *child4 = nullptr);
AstNode *clone() const;
@ -343,6 +350,24 @@ namespace AST
// to evaluate widths of dynamic ranges)
AstNode *clone_at_zero();
void set_attribute(RTLIL::IdString key, AstNode *node)
{
attributes[key] = node;
node->set_in_param_flag(true);
}
// helper to set in_lvalue/in_param flags from the hierarchy context (the actual flag
// can be overridden based on the intrinsic properties of this node, i.e. based on its type)
void set_in_lvalue_flag(bool flag, bool no_descend = false);
void set_in_param_flag(bool flag, bool no_descend = false);
// fix up the hierarchy flags (in_lvalue/in_param) of this node and its children
//
// to keep the flags in sync, fixup_hierarchy_flags(true) needs to be called once after
// parsing the AST to walk the full tree, then plain fixup_hierarchy_flags() performs
// localized fixups after modifying children/attributes of a particular node
void fixup_hierarchy_flags(bool force_descend = false);
// helper to print errors from simplify/genrtlil code
[[noreturn]] void input_error(const char *format, ...) const YS_ATTRIBUTE(format(printf, 2, 3));
};