[compiler-rt] r246454 - builtins: implement __emutls_get_address

[H.J. Lu via llvm-commits]

On Fri, Sep 4, 2015 at 8:15 AM, Joerg Sonnenberger via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> 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?
>

Why not use

typedef unsigned int gcc_word __attribute__((mode(word)));
typedef unsigned int gcc_pointer __attribute__((mode(pointer)));
typedef struct __emutls_control {
    gcc_word size;  /* size of the object in bytes */
    gcc_word align;  /* alignment of the object in bytes */
    union {
        gcc_pointer index;  /* data[index-1] is the object address */
        void* address;  /* object address, when in single thread env */
    } object;
    void* value;  /* null or non-zero initial value for the object */
} __emutls_control;

then?

-- 
H.J.