I put a drive-by comment on the bug, but here's my understanding:
gcc 4.4 now has -fstrict-aliasing on by default, whereas it was off by
default in 4.2.
gcc's behaviour, while annoying, is actually correct in this case: the C++
spec says that pointers to different types may not alias, and gcc
On Wed, Jan 13, 2010 at 9:12 AM, Stephen White senorbla...@chromium.org wrote:
2) Most of the supposed performance advantage of strict aliasing rules is
probably taken care of by memory disambiguation in modern (ie., Core2 and
later) CPUs.
I kind of doubt that. Disallowing aliasing lets the
Dan Kegel wrote:
On Wed, Jan 13, 2010 at 9:12 AM, Stephen White senorbla...@chromium.org
wrote:
2) Most of the supposed performance advantage of strict aliasing rules is
probably taken care of by memory disambiguation in modern (ie., Core2 and
later) CPUs.
I kind of doubt that.
On Wed, Jan 13, 2010 at 9:22 AM, Mark Mentovai m...@chromium.org wrote:
Dan Kegel wrote:
On Wed, Jan 13, 2010 at 9:12 AM, Stephen White senorbla...@chromium.org
wrote:
2) Most of the supposed performance advantage of strict aliasing rules is
probably taken care of by memory disambiguation
On Wed, Jan 13, 2010 at 9:42 AM, Evan Martin e...@chromium.org wrote:
With that in mind I think we should explicitly use
-fno-strict-aliasing until someone is willing to take the time to run
buildbots, track down regressions, etc.
+1 for -fno-strict-aliasing until someone fixes most/all of
the
On Wed, Jan 13, 2010 at 9:42 AM, Evan Martin e...@chromium.org wrote:
With that in mind I think we should explicitly use
-fno-strict-aliasing until someone is willing to take the time to run
buildbots, track down regressions, etc. for the other configuration.
I tend to agree. Many
On Wed, Jan 13, 2010 at 7:42 PM, Evan Martin e...@chromium.org wrote:
[snip]
With that in mind I think we should explicitly use
-fno-strict-aliasing until someone is willing to take the time to run
buildbots, track down regressions, etc. for the other configuration.
I have a patch to do this
On Wed, Jan 13, 2010 at 12:19 PM, Dan Kegel d...@kegel.com wrote:
On Wed, Jan 13, 2010 at 9:12 AM, Stephen White senorbla...@chromium.org
wrote:
2) Most of the supposed performance advantage of strict aliasing rules
is
probably taken care of by memory disambiguation in modern (ie., Core2
On Wed, Jan 13, 2010 at 10:06 AM, Stephen White senorbla...@chromium.orgwrote:
On Wed, Jan 13, 2010 at 12:19 PM, Dan Kegel d...@kegel.com wrote:
On Wed, Jan 13, 2010 at 9:12 AM, Stephen White senorbla...@chromium.org
wrote:
2) Most of the supposed performance advantage of strict aliasing
On Wed, Jan 13, 2010 at 9:42 AM, Evan Martin e...@chromium.org wrote:
At the code level I think it's not too hard for us to be aliasing
correct (people like Craig have already fixed all of the places where
we were wrong, and we have tools like bit_cast in basictypes.h to
make it not too
On Wed, Jan 13, 2010 at 8:34 PM, Antoine Labour pi...@google.com wrote:
On Wed, Jan 13, 2010 at 10:06 AM, Stephen White senorbla...@chromium.org
wrote:
On Wed, Jan 13, 2010 at 12:19 PM, Dan Kegel d...@kegel.com wrote:
On Wed, Jan 13, 2010 at 9:12 AM, Stephen White senorbla...@chromium.org
On Wed, Jan 13, 2010 at 10:53 AM, Craig Schlenter craig.schlen...@gmail.com
wrote:
On Wed, Jan 13, 2010 at 8:34 PM, Antoine Labour pi...@google.com wrote:
On Wed, Jan 13, 2010 at 10:06 AM, Stephen White
senorbla...@chromium.org
wrote:
On Wed, Jan 13, 2010 at 12:19 PM, Dan Kegel
On Wed, Jan 13, 2010 at 10:53 AM, Craig Schlenter craig.schlen...@gmail.com
wrote:
I'm one try-server run away from possibly turning -fno-strict-aliasing on
for
all linux/bsd gcc: http://codereview.chromium.org/519034
From a process standpoint, given that there is some disagreement here
is
I don't think that a firing squad will materialize over this change,
but if one does, I'll quell them for you.
LGTM in principle (but I haven't seen the actual change).
Mark
Craig Schlenter wrote:
On Wed, Jan 13, 2010 at 9:00 PM, Peter Kasting pkast...@google.com wrote:
On Wed, Jan 13, 2010
On Wed, Jan 13, 2010 at 11:22 AM, Craig Schlenter
craig.schlen...@chromium.org wrote:
Other than the immediate gain of hiding crbug.com/28749,
Which you have a patch (actually two, but one with r+) for, right?
I think the biggest
benefit is that end users relying on 4.4 builds are likely
On Wed, Jan 13, 2010 at 11:00 AM, Peter Kasting pkast...@google.com wrote:
On Wed, Jan 13, 2010 at 10:53 AM, Craig Schlenter
craig.schlen...@gmail.com wrote:
I'm one try-server run away from possibly turning -fno-strict-aliasing on
for
all linux/bsd gcc: http://codereview.chromium.org/519034
On Wed, Jan 13, 2010 at 11:28 AM, Evan Martin e...@chromium.org wrote:
PS: I'd be willing to flip the flag just after we do the next beta
channel push and see how many more problems we get because of it.
But in general, if it doesn't buy us any performance and it does cause
hard-to-track-down
On Wed, Jan 13, 2010 at 9:28 PM, Peter Kasting pkast...@google.com wrote:
On Wed, Jan 13, 2010 at 11:22 AM, Craig Schlenter
craig.schlen...@chromium.org wrote:
Other than the immediate gain of hiding crbug.com/28749,
Which you have a patch (actually two, but one with r+) for, right?
True. I
On Wed, Jan 13, 2010 at 12:07 PM, Craig Schlenter craig.schlen...@gmail.com
wrote:
Do we have other aliasing problems? If so my opinion changes.
There are some aliasing issues still in play. Off the top of my head:
1. unit_tests has what might be an issue in stl_tree.h or a compiler issue
In this bug
http://code.google.com/p/chromium/issues/detail?id=28749
It seems we're running afoul of a more finicky compiler not liking
some tricks we're playing with objects and memory in LazyInstance.
(You can skip down to comment #30 or so to get to the meat of it --
above that point we were
On Tue, Jan 12, 2010 at 10:15 AM, Craig Schlenter
craig.schlen...@chromium.org wrote:
On Tue, Jan 12, 2010 at 7:13 PM, Evan Martin e...@chromium.org wrote:
In this bug
http://code.google.com/p/chromium/issues/detail?id=28749
It seems we're running afoul of a more finicky compiler not
On Wed, Jan 13, 2010 at 8:07 AM, Antoine Labour pi...@google.com wrote:
On Tue, Jan 12, 2010 at 10:15 AM, Craig Schlenter
craig.schlen...@chromium.org wrote:
On Tue, Jan 12, 2010 at 7:13 PM, Evan Martin e...@chromium.org wrote:
In this bug
On Tue, Jan 12, 2010 at 10:37 PM, Craig Schlenter
craig.schlen...@chromium.org wrote:
That makes the compiler toss an aliasing error immediately:
cc1plus: warnings being treated as errors
base/rand_util_posix.cc: In function ‘uint64 base::RandUint64()’:
base/rand_util_posix.cc:32: error:
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