The Intel whitepaer[1] recommends using the RDSEED over RDRAND whenever
present. libstdc++ from GCC 10 will also use it in std::random_device.
[ChangeLog][QtCore][QRandomGenerator] The system() random generator will
now use the RDSEED instruction on x86 processors whenever available as
the first source of random data. It will fall back to RDRAND and then to
the system functions, in that order.
[1] https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide
Change-Id: I907a43cd9a714da288a2fffd15bab176e54e1975
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
GCC for 64-bit Windows has a bug that it fails to properly re-align the
stack pointer for use with 256-bit memory addresses (AVX). Therefore,
there's about a 50/50 chance that any function using AVX will have an
improperly-aligned stack. In release mode, stack accesses should be
rare, but in debug mode they happen frequently. Either way, this is a
ticking time bomb, so we disable.
Clang is not affected.
32-bit MinGW is not affected.
64-bit in other OSes with GCC are not affected.
Fixes: QTBUG-73539
Change-Id: Id061f35c088044b69a15fffd1580967808f31671
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Since the x86_simd/main.cpp file already has all the source for each and
every test anyway, just reuse it.
Change-Id: I938b024e38bf4aac9154fffd14f779f450827fb9
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
This has two main benefits:
1) introduces a qmake CONFIG we can use in .pro/.pri/.prf files
2) removes the need to keep an up-to-date list of which compilers
support the feature
The test is implemented as trying to compile every single SIMD test we
currently have, but without passing the -mXXX option. The reason for
trying all of them is that some people may have modified their mkspecs
to add -mXXX options or -march=XXX, which could enable the particular
feature we tried, resulting in a false positive outcome.
Change-Id: I938b024e38bf4aac9154fffd14f7784dc8d1f020
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
