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Re: PATCH [1/n] addr32: Properly use Pmode and word_mode
On Tue, Mar 6, 2012 at 6:40 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> >> >> We are expecting address to be 0x1001 - 1 == 0x1000. ?But, what we get
>>> >> >> is 0x1000 + 0xffffffff, not 0x1000 since 0x67 address prefix only applies to
>>> >> >> base register to zero-extend 0xffffffff to 64bit.
>>> >> >
>>> >> > I would call this a bug in the specification - I guess that
>>> >> > 0x1001(%eax) works correctly.
>>> >>
>>> >> This is how hardware works.
>>> >
>>> > Do you really need to use addr32 prefixes for the direct TLS seg refs?
>>> > Without that the addresses will be sign-extended from the 32-bit immediate
>>> > (which is used in LP64 x86_64 code too) and everything will work fine, won't
>>> > it?
>>> >
>>>
>>> 32bit immediate is OK. ?The problem is fs:(32bit register).
>>>
>>
>> Just require that the MEM uses DImode address in those patterns, even for -mx32?
>>
>
> Should SImode offset be zero-extended or sign-extended to
> DImode? The offset relative to TP can be negative. ?On the
> other hand, the upper 32bit address in x32 must be zero.
> Even if we properly extend it to DImode, it may not be faster
> than load fs:(reg) to a register first.
As I proposed earlier, just clear TARGET_TLS_DIRECT_SEG_REFS for now.
This will always load fs:0 to Pmode register and will add correctly
extended register or immediate to it. We can revisit this issue later
to specialize for fs:reg only, but I doubt it is worth any further
efforts.
Uros.
>
> --
> H.J.