[cfe-commits] r152608 - in /cfe/trunk: include/clang/AST/DeclBase.h lib/AST/DeclBase.cpp lib/Sema/SemaDecl.cpp lib/Sema/SemaDeclCXX.cpp lib/Sema/SemaDeclObjC.cpp lib/Sema/SemaLookup.cpp lib/Sema/SemaObjCProperty.cpp lib/Sema/SemaTemplate.cpp lib/Sema/SemaTemplateInstantiateDecl.cpp test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p11.cpp test/Modules/namespaces.cpp test/SemaCXX/PR10447.cpp

[John McCall]

On Mar 12, 2012, at 8:12 PM, Richard Smith wrote:
> Author: rsmith
> Date: Mon Mar 12 22:12:56 2012
> New Revision: 152608
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=152608&view=rev
> Log:
> Fix PR10447: lazily building name lookup tables for DeclContexts was broken.
> The deferred lookup table building step couldn't accurately tell which Decls
> should be included in the lookup table, and consequently built different tables
> in some cases.
> 
> Fix this by removing lazy building of DeclContext name lookup tables. In
> practice, the laziness was frequently not worthwhile in C++, because we
> performed lookup into most DeclContexts. In C, it had a bit more value,
> since there is no qualified lookup.
> 
> In the place of lazy lookup table building, we simply don't build lookup tables
> for function DeclContexts at all. Such name lookup tables are not useful, since
> they don't capture the scoping information required to correctly perform name
> lookup in a function scope.
> 
> The resulting performance delta is within the noise on my testing, but appears
> to be a very slight win for C++ and a very slight loss for C. The C performance
> can probably be recovered (if it is a measurable problem) by avoiding building
> the lookup table for the translation unit.

It seems that buildLookup is actually used by LLDB's external AST
source.  I don't really remember the details of why.  Richard, would you
mind working with Sean Callanan on this?

John.