Re: IVOPT improvement patch

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Jul 29, 2010 at 6:04 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> It looks strange:
>
> + ? ? ?width = (GET_MODE_BITSIZE (address_mode) < ?HOST_BITS_PER_WIDE_INT - 1)
> + ? ? ? ? ?? GET_MODE_BITSIZE (address_mode) : HOST_BITS_PER_WIDE_INT - 1;
> ? ? ? addr = gen_rtx_fmt_ee (PLUS, address_mode, reg1, NULL_RTX);
> - ? ? ?for (i = start; i <= 1 << 20; i <<= 1)
> + ? ? ?for (i = 1; i < width; i++)
> ? ? ? ?{
> - ? ? ? ? XEXP (addr, 1) = gen_int_mode (i, address_mode);
> + ? ? ? ? ?HOST_WIDE_INT offset = (1ll << i);
> + ? ? ? ? XEXP (addr, 1) = gen_int_mode (offset, address_mode);
> ? ? ? ? ?if (!memory_address_addr_space_p (mem_mode, addr, as))
> ? ? ? ? ? ?break;
> ? ? ? ?}
>
> HOST_WIDE_INT may be long or long long. "1ll" isn't always correct.
> I think width can be >= 31. Depending on HOST_WIDE_INT,
>
> HOST_WIDE_INT offset = -(1ll << i);
>
> may have different values. The whole function looks odd to me.
>
>

Here is a different approach to check address overflow.


-- 
H.J.
--
2010-07-29  H.J. Lu  <hongjiu.lu@intel.com>

	PR bootstrap/45119
	* tree-ssa-loop-ivopts.c (get_address_cost): Re-apply revision
	162652.  Check address overflow.

Attachment: gcc-pr45119-2.patch
Description: Text document