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Introduce VN_AS for downcasting to known AstNode subtype.

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VN_AS should be used over VN_CAST in code where the author knows up
front (i.e.: statically) what the true type of the node is. This has
multiple benefits over VN_CAST:
- In the debug build: Asserts node type is as expected
- In the optimized build: It is faster as no superfluous type test
- And (I would argue most importantly) it documents intent in the code

No current instances of VN_CAST changed in this patch
This commit is contained in:
Geza Lore 2021-10-16 19:29:38 +01:00
parent 749a66b7a2
commit ac622f9db8
1 changed files with 26 additions and 6 deletions
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32
src/V3Ast.h
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@ -60,15 +60,21 @@ using MTaskIdSet = std::set<int>; // Set of mtaskIds for Var sorting
if (VL_UNCOVERABLE(reasonp)) return reasonp; \
} while (false)
// (V)erilator (N)ode is: True if AstNode is of a a given AstType
// (V)erilator (N)ode is: Returns true iff AstNode is of the given AstNode subtype, and not
// nullptr.
#define VN_IS(nodep, nodetypename) (AstNode::privateIs<Ast##nodetypename>(nodep))
// (V)erilator (N)ode cast: Cast to given type if can; effectively
// dynamic_cast<nodetypename>(nodep)
// (V)erilator (N)ode cast: More efficient but otherwise same as dynamic_cast, use this instead.
// Cast to given type if node is of such type, otherwise returns nullptr.
#define VN_CAST(nodep, nodetypename) (AstNode::privateCast<Ast##nodetypename>(nodep))
#define VN_CAST_CONST(nodep, nodetypename) (AstNode::privateConstCast<Ast##nodetypename>(nodep))
#define VN_CAST_CONST(nodep, nodetypename) (AstNode::privateCastConst<Ast##nodetypename>(nodep))
// (V)erilator (N)ode deleted: Reference to deleted child (for assertions only)
// (V)erilator (N)ode as: Assert node is of given type then cast to that type. Node can be nullptr.
// Use this to downcast instead of VN_CAST when you know the true type of the node.
#define VN_AS(nodep, nodetypename) (AstNode::privateAs<Ast##nodetypename>(nodep))
#define VN_AS_CONST(nodep, nodetypename) (AstNode::privateAsConst<Ast##nodetypename>(nodep))
// (V)erilator (N)ode deleted: Pointer to deleted AstNode (for assertions only)
#define VN_DELETED(nodep) VL_UNLIKELY((vluint64_t)(nodep) == 0x1)
//######################################################################
@ -1851,9 +1857,23 @@ public:
return privateIs<T>(nodep) ? reinterpret_cast<T*>(nodep) : nullptr;
}
// For use via the VN_CAST_CONST macro only
template <typename T> inline static const T* privateConstCast(const AstNode* nodep) {
template <typename T> inline static const T* privateCastConst(const AstNode* nodep) {
return privateIs<T>(nodep) ? reinterpret_cast<const T*>(nodep) : nullptr;
}
// For use via the VN_AS macro only
template <typename T> inline static T* privateAs(AstNode* nodep) {
UASSERT_OBJ(!nodep || privateTypeTest<T>(nodep), nodep,
"AstNode is not of expected type, but instead has type '" << nodep->typeName()
<< "'");
return reinterpret_cast<T*>(nodep);
}
// For use via the VN_AS_CONST macro only
template <typename T> inline static const T* privateAsConst(const AstNode* nodep) {
UASSERT_OBJ(!nodep || privateTypeTest<T>(nodep), nodep,
"AstNode is not of expected type, but instead has type '" << nodep->typeName()
<< "'");
return reinterpret_cast<const T*>(nodep);
}
};
// Specialisations of privateIs/privateCast