[all-commits] [llvm/llvm-project] 45ea4d: [TableGen] Unify the priority of variables

[Wang Pengcheng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 45ea4d6256186b7869cd46907e88d8d2b1ea3df0
      https://github.com/llvm/llvm-project/commit/45ea4d6256186b7869cd46907e88d8d2b1ea3df0
  Author: wangpc <pc.wang at linux.alibaba.com>
  Date:   2023-05-24 (Wed, 24 May 2023)

  Changed paths:
    M llvm/docs/TableGen/ProgRef.rst
    M llvm/lib/TableGen/TGParser.cpp
    M llvm/lib/TableGen/TGParser.h
    M llvm/test/TableGen/defvar.td

  Log Message:
  -----------
  [TableGen] Unify the priority of variables

In D148197, we have made `defvar` statement able to refer to class
template arguments. However, the priority of class/multiclass
template argument is higher than variables defined by `defvar`, which
is a little counterintuitive.

In this patch, we unify the priority of variables. Each pair of
braces introduces a new scope, which may contain some additional
variables like template arguments, loop iterators, etc. We can
define local variables inside this scope via `defvar` and these
variables are of higher priority than additional variables. This
means that `defvar` will shadow additional variables with the same
name. The scope can be nested, and we use the innermost variable.

This make variables defined by `defvar` prior to class/multiclass
template arguments, loop iterators, etc. The shadow rules now are:

* `V` in a record body shadows a global `V`.

* `V` in a record body shadows template argument `V`.

* `V` in template arguments shadows a global `V`.

* `V` in a `foreach` statement list shadows any `V` in surrounding record or global scopes.

Reviewed By: tra

Differential Revision: https://reviews.llvm.org/D149016