hokein created this revision.
hokein added reviewers: sammccall, usaxena95.
Herald added a project: All.
hokein requested review of this revision.
Herald added a subscriber: alextsao1999.
Herald added a project: clang-tools-extra.
See https://reviews.llvm.org/D130626 for details;
A prototype to eliminate "local" identifier ambiguties in the grammar:
- use a unified type-name instead, and remove all different type rules (
class-name/enum-name/typedef-name), this eliminates the top#1 type-name
ambiguity;
- use a generic identifier for nested-name-specifier, and don't distinguish
with the type-name and namespace-name cases;
- remove template-name rule, it is mainly used for the template argument
deduction in simple-type-specifier, it has the same syntax with type-name,
merged with type-name case;
After this patch, remaining ambiguities are real ambiguities in C++:
Some numbers with this patch:
| file | ambiguous nodes | forest size | glrParse
performance |
| SemaCodeComplete.cpp | 1.1w -> 2k | 10.4MB -> 7.12MB | 7.1MB/s -> 11MB/s
|
| AST.cpp | 1.3k -> 286 | 0.99MB -> 0.68MB | 6.7MB/s ->
9.9MB/s |
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D130747
Files:
clang-tools-extra/pseudo/lib/cxx/CXX.cpp
clang-tools-extra/pseudo/lib/cxx/cxx.bnf
Index: clang-tools-extra/pseudo/lib/cxx/cxx.bnf
===================================================================
--- clang-tools-extra/pseudo/lib/cxx/cxx.bnf
+++ clang-tools-extra/pseudo/lib/cxx/cxx.bnf
@@ -34,15 +34,15 @@
_ := declaration-seq
# gram.key
-typedef-name := IDENTIFIER
-typedef-name := simple-template-id
+#typedef-name := IDENTIFIER
+#typedef-name := simple-template-id
namespace-name := IDENTIFIER
-namespace-name := namespace-alias
-namespace-alias := IDENTIFIER
-class-name := IDENTIFIER
-class-name := simple-template-id
-enum-name := IDENTIFIER
-template-name := IDENTIFIER
+#namespace-name := namespace-alias
+#namespace-alias := IDENTIFIER
+#class-name := IDENTIFIER
+#class-name := simple-template-id
+#enum-name := IDENTIFIER
+#template-name := IDENTIFIER
# gram.basic
#! Custom modifications to eliminate optional declaration-seq
@@ -69,8 +69,10 @@
unqualified-id := template-id
qualified-id := nested-name-specifier TEMPLATE_opt unqualified-id
nested-name-specifier := :: [guard]
-nested-name-specifier := type-name ::
-nested-name-specifier := namespace-name ::
+#nested-name-specifier := type-name ::
+#nested-name-specifier := namespace-name ::
+nested-name-specifier := IDENTIFIER ::
+nested-name-specifier := simple-template-id ::
nested-name-specifier := decltype-specifier ::
nested-name-specifier := nested-name-specifier IDENTIFIER ::
nested-name-specifier := nested-name-specifier TEMPLATE_opt simple-template-id ::
@@ -374,7 +376,7 @@
simple-type-specifier := nested-name-specifier TEMPLATE simple-template-id
simple-type-specifier := decltype-specifier
simple-type-specifier := placeholder-type-specifier
-simple-type-specifier := nested-name-specifier_opt template-name
+#simple-type-specifier := nested-name-specifier_opt template-name
simple-type-specifier := builtin-type
builtin-type := CHAR
builtin-type := CHAR8_T
@@ -390,9 +392,12 @@
builtin-type := FLOAT
builtin-type := DOUBLE
builtin-type := VOID
-type-name := class-name
-type-name := enum-name
-type-name := typedef-name
+#type-name := class-name
+#type-name := enum-name
+#type-name := typedef-name
+type-name := IDENTIFIER
+type-name := simple-template-id
+
elaborated-type-specifier := class-key nested-name-specifier_opt IDENTIFIER
elaborated-type-specifier := class-key simple-template-id
elaborated-type-specifier := class-key nested-name-specifier TEMPLATE_opt simple-template-id
@@ -550,7 +555,8 @@
class-specifier := class-head { member-specification_opt [recover=Brackets] }
class-head := class-key class-head-name class-virt-specifier_opt base-clause_opt
class-head := class-key base-clause_opt
-class-head-name := nested-name-specifier_opt class-name
+class-head-name := nested-name-specifier_opt IDENTIFIER
+class-head-name := nested-name-specifier_opt simple-template-id
class-virt-specifier := contextual-final
class-key := CLASS
class-key := STRUCT
@@ -674,7 +680,7 @@
type-parameter-key := TYPENAME
type-constraint := nested-name-specifier_opt concept-name
type-constraint := nested-name-specifier_opt concept-name < template-argument-list_opt >
-simple-template-id := template-name < template-argument-list_opt >
+simple-template-id := IDENTIFIER < template-argument-list_opt >
template-id := simple-template-id
template-id := operator-function-id < template-argument-list_opt >
template-id := literal-operator-id < template-argument-list_opt >
@@ -684,7 +690,7 @@
template-argument := type-id
template-argument := id-expression
constraint-expression := logical-or-expression
-deduction-guide := explicit-specifier_opt template-name ( parameter-declaration-list_opt ) -> simple-template-id ;
+deduction-guide := explicit-specifier_opt IDENTIFIER ( parameter-declaration-list_opt ) -> simple-template-id ;
concept-definition := CONCEPT concept-name = constraint-expression ;
concept-name := IDENTIFIER
typename-specifier := TYPENAME nested-name-specifier IDENTIFIER
Index: clang-tools-extra/pseudo/lib/cxx/CXX.cpp
===================================================================
--- clang-tools-extra/pseudo/lib/cxx/CXX.cpp
+++ clang-tools-extra/pseudo/lib/cxx/CXX.cpp
@@ -235,10 +235,8 @@
// simple-type-specifier
case rule::simple_type_specifier::type_name:
- case rule::simple_type_specifier::template_name:
case rule::simple_type_specifier::builtin_type:
case rule::simple_type_specifier::nested_name_specifier__TEMPLATE__simple_template_id:
- case rule::simple_type_specifier::nested_name_specifier__template_name:
case rule::simple_type_specifier::nested_name_specifier__type_name:
case rule::simple_type_specifier::decltype_specifier:
case rule::simple_type_specifier::placeholder_type_specifier:
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