expand/recog/match question

Ian Lance Taylor iant@google.com
Tue Aug 27 08:39:00 GMT 2013


On Mon, Aug 26, 2013 at 7:51 PM, Hendrik Greving
<hendrik.greving.intel@gmail.com> wrote:
>
> GCC 4.8.1 generates a movsi like this when compiling newlib with my backend:
>
> gdb) call debug_rtx(operand0)
> (reg:SI 356)
> (gdb) call debug_rtx(operand1)
> (const:SI (plus:SI (symbol_ref:SI ("_ctype_locale_buf") <var_decl
> 0x2aaaab15d558 _ctype_locale_buf>)
>         (const_int 32 [0x20])))
>
> Any idea why the compiler tries to store such a weird construct? Is it
> weird actually, or normal? I am trying to figure out if I either
> allowed too much at some point (predicates?) or too little (do I need
> to handle this with instructions?)?

This seems normal enough to me.  It's basically
    move reg356, $_ctype_locale_buf+32
Here _ctype_locale_buf+32 is an immediate value which is known at link
time.

You will get this kind of thing from code like
    p = &_ctype_locale_buf[32];
if _ctype_locale_buf is a char array.

Ian



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