rmaz created this revision.
rmaz requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
This diff will de-duplicate methods read from AST files before
inserting them in to a global method pool list. When reading
ObjCMethodDecl from AST files we can end up with a significant
amount of duplication when modules contain redeclarations of
system framework methods. For instance a common pattern is to
redeclare `-(instancetype)init` with `NS_UNAVAILABLE`, which
results in the entire ObjCMethodList for `init` being serialized
in each module with this redeclaration.
Measuring this against our codebase for files that use `-fmodules`
shows an overall 19% compile time improvement, and in some cases
as much as 79% for files with a lot of modular dependencies.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D109632
Files:
clang/lib/Serialization/ASTReader.cpp
Index: clang/lib/Serialization/ASTReader.cpp
===================================================================
--- clang/lib/Serialization/ASTReader.cpp
+++ clang/lib/Serialization/ASTReader.cpp
@@ -8181,8 +8181,18 @@
/// Add the given set of methods to the method list.
static void addMethodsToPool(Sema &S, ArrayRef<ObjCMethodDecl *> Methods,
ObjCMethodList &List) {
- for (unsigned I = 0, N = Methods.size(); I != N; ++I) {
- S.addMethodToGlobalList(&List, Methods[I]);
+ // Methods from visited modules can contain a lot of duplicates
+ // when redeclaring methods from system frameworks, for example
+ // when marking -(instancetype)init as NS_UNAVAILABLE.
+ llvm::DenseSet<ObjCMethodDecl *> seen;
+ for (auto *L = &List; L; L = L->getNext()) {
+ seen.insert(L->getMethod());
+ }
+
+ for (auto *M : Methods) {
+ if (seen.insert(M).second) {
+ S.addMethodToGlobalList(&List, M);
+ }
}
}
Index: clang/lib/Serialization/ASTReader.cpp
===================================================================
--- clang/lib/Serialization/ASTReader.cpp
+++ clang/lib/Serialization/ASTReader.cpp
@@ -8181,8 +8181,18 @@
/// Add the given set of methods to the method list.
static void addMethodsToPool(Sema &S, ArrayRef<ObjCMethodDecl *> Methods,
ObjCMethodList &List) {
- for (unsigned I = 0, N = Methods.size(); I != N; ++I) {
- S.addMethodToGlobalList(&List, Methods[I]);
+ // Methods from visited modules can contain a lot of duplicates
+ // when redeclaring methods from system frameworks, for example
+ // when marking -(instancetype)init as NS_UNAVAILABLE.
+ llvm::DenseSet<ObjCMethodDecl *> seen;
+ for (auto *L = &List; L; L = L->getNext()) {
+ seen.insert(L->getMethod());
+ }
+
+ for (auto *M : Methods) {
+ if (seen.insert(M).second) {
+ S.addMethodToGlobalList(&List, M);
+ }
}
}
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