[pseudo] Eliminate the type-name identifier ambiguities in the grammar.
See https://reviews.llvm.org/D130626 for motivation.
Identifier in the grammar has different categories (type-name, template-name,
namespace-name), they requires semantic information to resolve. This patch is
to eliminate the "local" ambiguities in type-name, and namespace-name, which
gives us a performance boost of the parser:
- eliminate all different type rules (class-name, enum-name, typedef-name), and
fold them into a unified type-name, this removes the #1 type-name ambiguity, and
gives us a big performance boost;
- remove the namespace-alis rules, as they're hard and uninteresting;
Note that we could eliminate more and gain more performance (like fold template-name,
type-name, namespace together), but at current stage, we'd like keep all existing
categories of the identifier (as they might assist in correlated disambiguation &
keep the representation of important concepts uniform).
| file |ambiguous nodes | forest size | glrParse performance |
|SemaCodeComplete.cpp| 11k -> 5.7K | 10.4MB -> 7.9MB | 7.1MB/s -> 9.98MB/s |
| AST.cpp | 1.3k -> 0.73K | 0.99MB -> 0.77MB | 6.7MB/s -> 8.4MB/s |
Differential Revision: https://reviews.llvm.org/D130747