Hi all， Clang use a hash table to store all its identifiers. The hash table definition is: typedef llvm::StringMap<IdentifierInfo*, llvm::BumpPtrAllocator> HashTableTy; HashTableTy HashTable; Can anyone explain the mechnism of handling the name string key collision for me? Is there a IdentifierInfo objects chain or list for variable or function with the same name? Thanks very much! Yabin -- The question is how do you generate these offline annotations and how expensive and accurate they are and why they are usefil in which applications? -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20100726/73026dc0/attachment.html>
On Jul 25, 2010, at 11:27 PM, Yabin Hu wrote:> Clang use a hash table to store all its identifiers. The hash table definition is: > > typedef llvm::StringMap<IdentifierInfo*, llvm::BumpPtrAllocator> HashTableTy; > HashTableTy HashTable; > > Can anyone explain the mechnism of handling the name string key collision for me? Is there a IdentifierInfo objects chain or list for > variable or function with the same name?This hash table is just used to unique IdentifierInfos. IdentifierInfo itself holds a client-specific pointer of storage; Sema uses that pointer to hold either a NamedDecl* or an IdDeclInfo*, which we distinguish with the usual low-bit tagging trick. IdDeclInfo is basically a SmallVector<NamedDecl*,2>. There's some extra magic to make macros/PCH not require redundant hashes, but that's the basic idea. Anyway, this is all sufficient to implement unqualified lookup in C and Objective C, but our C++ implementation can only get away with relying on IdentifierInfo when looking in a function; we have to fall back on DeclContext lookups (i.e. rehashing the string in different hash tables) when looking into pretty much any other kind of scope. John.
On 07/25/2010 11:27 PM, Yabin Hu wrote:> Hi all， > > Clang use a hash table to store all its identifiers. The hash table > definition is: > > typedef llvm::StringMap<IdentifierInfo*, llvm::BumpPtrAllocator> > HashTableTy; > HashTableTy HashTable; > > Can anyone explain the mechnism of handling the name string key > collision for me? Is there a IdentifierInfo objects chain or list for > variable or function with the same name? >Queries about Clang should be sent to clang-dev, not llvm-dev. Sebastian