This is extremely useful, since the most common action after a failed
compare-and-swap is to loop around, trying again with the current
value as found in memory.
Code currently written as:
do {
Type value = atomic.load();
...
} while (!atomic.testAndSetRelaxed(value, desired));
Becomes:
Type value = atomic.load();
do {
...
} while (!atomic.testAndSetRelaxed(value, desired, value));
In most CPU architectures, the value that was found in memory is known
to the compare-and-swap code, so this is more efficient than the
previous code. In architectures where the value is not known, the new
code is no worse than before.
The implementation sometimes modified an existing function, sometimes
it added a new one, depending on whether more registers were needed in
the assembly (like ARMv6-7), the code became more complex (ARMv5), the
optimizer failed (C++11), or it was just plain equivalent (MIPS).
Change-Id: I7d6d200ea9746ec8978a0c1e1969dbc3580b9285
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This simplifies the code a lot and avoids silly mistakes where a
specific integer type is missing (such as char16_t).
Change-Id: Id91dfd1919e783e0a9af7bfa093ca560a01b22d1
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Change copyrights and license headers from Nokia to Digia
Change-Id: If1cc974286d29fd01ec6c19dd4719a67f4c3f00e
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Those are regular, integer types, of 16- and 32-bit width,
respectively. C++11's std::atomic supports them, so we should too.
C++11 also supports wchar_t, but since that type's size can change, I
don't feel like support for it in Qt is pressing.
Change-Id: I945b641c91a8a98be82715f878c382dee58ac98b
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
This allows one to write code that depends on these values at
compile-time.
Change-Id: I7d78524ed9c70d4141360496d1d764dcbfa92e62
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Qt 5.0 beta requires changing the default to the 5.0 API, disabling
the deprecated code. However, tests should test (and often do) the
compatibility API too, so turn it back on.
Task-number: QTBUG-25053
Change-Id: I8129c3ef3cb58541c95a32d083850d9e7f768927
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Test that they do expand properly and don't produce errors. This is
templated code, so it doesn't get tested fully unless we instantiate
them.
Also check that the alignments are correct.
Change-Id: I2a8ee2165167f54b652b4227411e209850974b8e
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>
As in the past, to avoid rewriting various autotests that contain
line-number information, an extra blank line has been inserted at the
end of the license text to ensure that this commit does not change the
total number of lines in the license header.
Change-Id: I311e001373776812699d6efc045b5f742890c689
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>
These comments were mostly empty or inaccurate. Appropriate naming of
tests and appropriate placement of tests within the directory tree
provide more reliable indicators of what is being tested.
Change-Id: Ib6bf373d9e79917e4ab1417ee5c1264a2c2d7027
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>
This is a source incompatible change. There is concern that the
convenience of the implicit cast and assignment operators can lead to
misuse. Several commits have already been done that remove excess use
of the implicit cast, which is a *volatile* read every time it's used.
Users of the QAtomic* API should have to think about when they are
loading the value, and if they do or don't need the acquire memory
barrier on load. The code that people would write using this API is
meant to be multi-threaded, concurrent, and correct. The API should not
allow them to inadvertently, possibly unknowingly, shoot themselves
in the foot.
SC-break-rubber-stamped-by: Lars Knoll
Change-Id: I88fbc26d9db7b5ec80a58ad6271ffa13bbfd191f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Use QAtomic*::load() and ::store() instead of the deprecated
cast, assignment, and comparison operators. These will be removed
in the near future.
The tests for these particular operators have not been changed,
though, as the change to remove the operators will also remove
the respective tests.
Change-Id: I2f24d18992af0c6e0f487d707218e4e84f4bdd12
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>
qttest_p4.prf was added as a convenience for Qt's own autotests in Qt4.
It enables various crufty undocumented magic, of dubious value.
Stop using it, and explicitly enable the things from it which we want.
Change-Id: I7c1ffe9c8c294dbdc988e1582e580b1ed3f4593e
Reviewed-by: Jason McDonald <jason.mcdonald@nokia.com>
