[ImportVerilog] Add assign and pre/post increment/decrement expressions #6859
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maerhart
approved these changes
Mar 21, 2024
| @@ -53,6 +53,13 @@ struct ExprVisitor { | |||
| return {}; | |||
| } | |||
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| // Handle references to the left-hand side of a parent assignment. | |||
| Value visit(const slang::ast::LValueReferenceExpression &expr) { | |||
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Do continuous assignments use a different system for lvalues or can they not be nested?
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They don't allow for the += syntax. += is always a blocking assignment within a procedural block.
Add support for pre and post increment and decrement expressions, like `x++` and `--x`, as well as assign expressions, like `a += 5`. Slang represents these assignments as `Assign(a, Add(LValueRef, 5))` in the AST. The `LValueRef` node contextually refers to the parent assignment's left-hand side. To deal with this, also add a corresponding lvalue stack to the conversion context. Assignments push and pop their lvalues onto and off of this stack. These expressions require a mechanism in the IR to express _when_ a variable is read. To capture this, add a new `moore.read_lvalue` op. It currently looks like an identity operation with a `MemRead` side effect. Further down the road, we may want to introduce a proper reference type for variables, ports, nets, and other things, and have `read_lvalue` and the various assigns operate on that type instead. This sets the foundation for that. Co-authored-by: Hailong Sun <hailong.sun@terapines.com> Co-authored-by: ShiZuoye <albertethon@163.com> Co-authored-by: hunterzju <hunter_ht@zju.edu.cn> Co-authored-by: Anqi Yu <anqi.yu@terapines.com>
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Add support for pre and post increment and decrement expressions, like
x++and--x, as well as assign expressions, likea += 5. Slang represents these assignments asAssign(a, Add(LValueRef, 5))in the AST. TheLValueRefnode contextually refers to the parent assignment's left-hand side. To deal with this, also add a corresponding lvalue stack to the conversion context. Assignments push and pop their lvalues onto and off of this stack.These expressions require a mechanism in the IR to express when a variable is read. To capture this, add a new
moore.read_lvalueop. It currently looks like an identity operation with aMemReadside effect. Further down the road, we may want to introduce a proper reference type for variables, ports, nets, and other things, and haveread_lvalueand the various assigns operate on that type instead. This sets the foundation for that.