On 02/26/2014 04:43 PM, Segher Boessenkool wrote:
> "+r"(p) as well, you're modifying %2.
Yes, yes, OK. :-)
Andrew.
FWIW:
> __asm__("\t0:\n"
> "\tstr wzr, [%2, #4]!\n"
> "\tsub %1, %1, #1\n"
> "\tcbnz %1, 0b\n"
> : "=m"(*p), "+r"(len) : "r"(p));
"+r"(p) as well, you're modifying %2.
Cheers,
Segher
Michael Matz writes:
> On Wed, 26 Feb 2014, Richard Biener wrote:
>> > "\tstr wzr, [%2, #4]!\n"
>> > "\tsub %1, %1, #1\n"
>> > "\tcbnz %1, 0b\n"
>> > : "=m"(*p), "+r"(len) : "r"(p));
>> >
>> > I presume this is wrong because *p only refers to p[0]. Is it
>>
Hi,
On Wed, 26 Feb 2014, Richard Biener wrote:
> > "\tstr wzr, [%2, #4]!\n"
> > "\tsub %1, %1, #1\n"
> > "\tcbnz %1, 0b\n"
> > : "=m"(*p), "+r"(len) : "r"(p));
> >
> > I presume this is wrong because *p only refers to p[0]. Is it
> > possible to tell GCC t
On 02/26/2014 12:24 PM, Richard Biener wrote:
> An additional question that immediately pops up here is that
> of TBAA - may we use the alias-set of the memory reference
> to disambiguate other loads/stores against the asm?
I would certainly hope so: I don't think the rule here should be any
diffe
On Wed, Feb 26, 2014 at 12:10 PM, Andrew Haley wrote:
> On 02/26/2014 10:51 AM, Richard Biener wrote:
>> But yes, technically you write p[0] here but as "m" merely builds
>> an address to the memory I'd say that we have to treat any "m"
>> operand as possibly reading from / writing to / clobbering
On 02/26/2014 10:51 AM, Richard Biener wrote:
> But yes, technically you write p[0] here but as "m" merely builds
> an address to the memory I'd say that we have to treat any "m"
> operand as possibly reading from / writing to / clobbering the
> whole object that can be refered to using that addres
On Wed, Feb 26, 2014 at 11:32 AM, Andrew Haley wrote:
> Say you have a pointer:
>
> int *p;
>
> and an inline asm that writes to a block of memory
>
> __asm__("\t0:\n"
> "\tstr wzr, [%2, #4]!\n"
> "\tsub %1, %1, #1\n"
> "\tcbnz %1, 0b\n"
> : "=m"(*p), "+r"
Say you have a pointer:
int *p;
and an inline asm that writes to a block of memory
__asm__("\t0:\n"
"\tstr wzr, [%2, #4]!\n"
"\tsub %1, %1, #1\n"
"\tcbnz %1, 0b\n"
: "=m"(*p), "+r"(len) : "r"(p));
I presume this is wrong because *p only refers to p[0].
