[compiler-rt] r246454 - builtins: implement __emutls_get_address

[Joerg Sonnenberger via llvm-commits]

On Fri, Sep 04, 2015 at 08:00:34AM -0700, H.J. Lu via llvm-commits wrote:
> > +/* Emulated TLS objects are always allocated at run-time. */
> > +static inline void* emutls_allocate_object(__emutls_control* control) {
> > +    /* Use standard C types, check with gcc's emutls.o. */
> > +    typedef unsigned int gcc_word __attribute__((mode(word)));
> > +    typedef unsigned int gcc_pointer __attribute__((mode(pointer)));
> > +    COMPILE_TIME_ASSERT(sizeof(size_t) == sizeof(gcc_word));
> 
> What is this assert for?  It is false for x32 where size_t is 4 bytes and
> gcc_word 8 bytes.

To ensure that the struct layout is ABI compatible. So what layout does
GCC use?

Joerg