For projects depending on LLVM, I find it very useful to combine a
release-no-asserts build of LLVM with a debug+asserts build of the dependent
project. The motivation is that when developing a dependent project, you are
debugging that project itself, not LLVM. In my usecase, a significant part of
the runtime is spent in LLVM optimization passes, so I would like to build LLVM
without assertions to get the best performance from this combination.
Currently, `lib/Support/Debug.cpp` changes the set of symbols it provides
depending on NDEBUG, while `include/llvm/Support/Debug.h` requires extra
symbols when NDEBUG is not defined. Thus, it is not possible to enable
assertions in an external project that uses facilities of `Debug.h`.
This patch changes `Debug.cpp` and `Valgrind.cpp` to always define the symbols
that other code may depend on when #including LLVM headers without NDEBUG.
http://reviews.llvm.org/D7662
llvm-svn: 229819
That causes references to them to be weak references which can collapse
to null if no definition is provided. We call these functions
unconditionally, so a definition *must* be provided. Make the
definitions provided in the .cpp file weak by re-declaring them as weak
just prior to defining them. This should keep compilers which cannot
attach the weak attribute to the definition happy while actually
resolving the symbols correctly during the link.
You might ask yourself upon reading this commit log: how did *any* of
this work before? Well, fun story. It turns out we have some code in
Support (BumpPtrAllocator) which both uses virtual dispatch and has
out-of-line vtables used by that virtual dispatch. If you move the
virtual dispatch into its header in *just* the right way, the optimizer
gets to devirtualize, and remove all references to the vtable. Then the
sad part: the references to this one vtable were the only strong symbol
uses in the support library for llvm-tblgen AFAICT. At least, after
doing something just like this, these symbols stopped getting their weak
definition and random calls to them would segfault instead.
Yay software.
llvm-svn: 205137
These annotations are disabled entirely when either ENABLE_THREADS is off, or
building a release build. When enabled, they add calls to functions with no
statements to ManagedStatic's getters.
Use these annotations to inform tsan that the race used inside ManagedStatic
initialization is actually benign. Thanks to Kostya Serebryany for helping
write this patch!
llvm-svn: 144567
