Hi,
On Thu, 31 Mar 2011, Jeff Law wrote:
> Without trip count estimates the speculative read can introduce a
> performance regression.
Like any other transformation. So what are you trying to say? That
therefore introducing a mode in GCC disallowing any speculative reads
(even if they happe
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On 03/31/11 07:26, Richard Guenther wrote:
> On Thu, Mar 31, 2011 at 3:08 PM, Jeff Law wrote:
> On 03/24/11 17:57, Andrew MacLeod wrote:
My fault for not being specific about it... I tend to just use data race
as a catch all for all these ty
On Thu, Mar 31, 2011 at 3:08 PM, Jeff Law wrote:
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> On 03/24/11 17:57, Andrew MacLeod wrote:
>> My fault for not being specific about it... I tend to just use data race
>> as a catch all for all these types of things when talking about them
>> wit
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On 03/24/11 17:57, Andrew MacLeod wrote:
> My fault for not being specific about it... I tend to just use data race
> as a catch all for all these types of things when talking about them
> with Aldy.
>
> the testcase should have for (x=0; x< limi
On 03/25/11 10:39, Richard Guenther wrote:
On Fri, Mar 25, 2011 at 4:33 PM, Jakub Jelinek wrote:
On Fri, Mar 25, 2011 at 09:30:22AM -0600, Jeff Law wrote:
I'm not going to chime in on this specific problem; however, it is worth
noting that many of the issues raised by the C++0x memory model al
On Fri, Mar 25, 2011 at 4:33 PM, Jakub Jelinek wrote:
> On Fri, Mar 25, 2011 at 09:30:22AM -0600, Jeff Law wrote:
>> I'm not going to chime in on this specific problem; however, it is worth
>> noting that many of the issues raised by the C++0x memory model also
>> affect the linux kernel.
>
> But
On Fri, Mar 25, 2011 at 09:30:22AM -0600, Jeff Law wrote:
> I'm not going to chime in on this specific problem; however, it is worth
> noting that many of the issues raised by the C++0x memory model also
> affect the linux kernel.
But what they are seeing are certainly store data races, not load r
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On 03/25/11 09:20, Michael Matz wrote:
> Even if there was such (IMO useless) hardware, or somebody would waste his
> time in writing such (equally useless) virtual machine that can detect
> fabricated problems somebody invented for some standard th
Hi,
On Fri, 25 Mar 2011, Aldy Hernandez wrote:
> > But speculative loads are never a problem. So I'd like to avoid
> > cluttering GCC code with stuff to avoid them. I honestly don't care
> > about diagnostic tools that fail to see if a value read is used or
> > not.
>
> Frankly, I agree. T
But hoisting global in this case doesn't result in a data race, since the
loop always accesses global and contains no synchronisation code. If it
were only accessed conditionally, as in the examples under "Avoiding
Speculation" on that page, then there would be a race in hoisting it, but
not fo
On Fri, Mar 25, 2011 at 12:57 AM, Andrew MacLeod wrote:
>> On Thu, 24 Mar 2011, Aldy Hernandez wrote:
>>
>>> This work is independent of the C++ memory model. It is just to prevent
>>> the
>>> optimizers from introducing new data races due to code movement. This
>>> initial
>>> pass is just to ma
On Thu, 24 Mar 2011, Aldy Hernandez wrote:
This work is independent of the C++ memory model. It is just to prevent the
optimizers from introducing new data races due to code movement. This initial
pass is just to make the optimizations data race safe so that if you have a
program which is prove
On Thu, 24 Mar 2011, Aldy Hernandez wrote:
> This work is independent of the C++ memory model. It is just to prevent the
> optimizers from introducing new data races due to code movement. This initial
> pass is just to make the optimizations data race safe so that if you have a
> program which is
On 03/24/11 14:58, Richard Henderson wrote:
On 03/24/2011 10:33 AM, Aldy Hernandez wrote:
In the example below we usually hoist "global" into a register or
temporary to avoid reading from it at each step. This would cause a
race if another thread had modified "global" in between iterations.
On 03/24/2011 10:33 AM, Aldy Hernandez wrote:
> In the example below we usually hoist "global" into a register or
> temporary to avoid reading from it at each step. This would cause a
> race if another thread had modified "global" in between iterations.
>
> for (x=0; x< 5; x++)
> sum[x
This is my first stab at disallowing load data races that happen when we
cache the value of a global. I would appreciate input before
committing, especially on the RTL bits, cause it's been quite a while
since I typed d-e-b-u-g-_-r-t-x. :-)
In the example below we usually hoist "global" into
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