Displaying 6 results from an estimated 6 matches for "datarac".
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2013 May 12
0
[LLVMdev] Predicated Vector Operations
...machine without
false sharing and cache coherency issues when trying to determine if two
operations form a data race.
>
> Of course this assumes that thread B won't access the element stored by
> thread A and vice versa.
>
If we assume that, we have the conclusion -- there is on datarace. The
entire question is whether or not the masked element is notionally "stored"
(but without changing the value afterward), or not.
>From Nadav's link, for example, it appears that AVX *does* actually do a
full store of the 256-bit vector, but it does it atomically which preclud...
2013 May 09
4
[LLVMdev] Predicated Vector Operations
...ccess the element stored by
thread A and vice versa.
> From a memory model perspective, if this does *not* form a data race,
> that makes this tremendously more complex to implement, analyze, and
> optimize... I'm somewhat hopeful that the desired semantics are for
> this to form a datarace (and thus require synchronization when
> occurring in different threads like this).
Most of the time the compiler will not know the mask value and will have
to be conservative. As Nadav has pointed out, what constitutes
"conservative" is entirely context-dependent.
But I don't...
2013 May 09
0
[LLVMdev] Predicated Vector Operations
...threads and their masked stores, does this form a data race or not?
>From a memory model perspective, if this does *not* form a data race, that
makes this tremendously more complex to implement, analyze, and optimize...
I'm somewhat hopeful that the desired semantics are for this to form a
datarace (and thus require synchronization when occurring in different
threads like this).
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2013 May 08
4
[LLVMdev] Predicated Vector Operations
On May 8, 2013, at 4:00 PM, Eric Christopher <echristo at gmail.com> wrote:
>
> Thinking that a masked store is conservatively a store of the full
> width of the store right?
It depends on the optimization. Consider this example:
masked_store(Val, Ptr , M)
X = masked_load(Ptr, M2)
If you assume that your store actually overwrites everything in that memory location then you
2013 May 09
0
[LLVMdev] Predicated Vector Operations
...gt; thread A and vice versa.
>
> > From a memory model perspective, if this does *not* form a data race,
> > that makes this tremendously more complex to implement, analyze, and
> > optimize... I'm somewhat hopeful that the desired semantics are for
> > this to form a datarace (and thus require synchronization when
> > occurring in different threads like this).
>
> Most of the time the compiler will not know the mask value and will have
> to be conservative. As Nadav has pointed out, what constitutes
> "conservative" is entirely context-depe...
2013 Nov 09
1
[LLVMdev] Proposal for safe-to-execute meta-data for heap accesses
On Nov 8, 2013, at 9:36 PM, Chandler Carruth <chandlerc at google.com> wrote:
>
> On Fri, Nov 8, 2013 at 8:44 AM, Filip Pizlo <fpizlo at apple.com> wrote:
>> Is the expectation that to utilize this metadata an optimization pass would have to inspect the body of @f and reason about its behavior given <args>?
>
> Yes.
>
>>
>> If so, then I