Re: [PATCH v2 3/3] Add ffsl(), ffsll(), fls(), flsl(), flsll()

[Sebastian Huber <sebastian dot huber at embedded-brains dot de>]

On 27/07/17 09:06, Sebastian Huber wrote:

> On 27/07/17 08:52, Kito Cheng wrote:
>
> > I only hit this bug on RV64, you can try -march=rv64ima -mabi=lp64
> > with riscv32-elf-gcc if you don't want to rebuild.
>
> Yes, I get the same. Is this a GCC bug?

No, its a feature:

/* Call this to initialize the contents of the optabs
   appropriately for the current target machine.  */

void
init_optabs (void)
{
[...]
  /* The ffs function operates on `int'.  Fall back on it if we do not
     have a libgcc2 function for that width.  */
  if (INT_TYPE_SIZE < BITS_PER_WORD)
    set_optab_libfunc (ffs_optab, mode_for_size (INT_TYPE_SIZE, 
MODE_INT, 0),
               "ffs");

I guess we have to use some conditional compilation in ffs() to work 
around this GCC feature.

--
Sebastian Huber, embedded brains GmbH

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