diff options
| author | Thiago Macieira <thiago.macieira@intel.com> | 2024-09-27 09:52:15 -0700 |
|---|---|---|
| committer | Thiago Macieira <thiago.macieira@intel.com> | 2024-10-04 10:45:21 -0700 |
| commit | 6543f50536f3547b43a27b32af59d68f28a60247 (patch) | |
| tree | 87c89d4eabbdce70dae2af2da8ea946d11f90177 /src/corelib/global/qsimd.cpp | |
| parent | f85a17abeb1e9464492eb57cbb772683d6c8093d (diff) | |
Remove dead code in checkRdrndWorks() if __RDRND__ is defined
The only place where we call qRandomCpu() in qrandom.cpp is guarded by a
check using qCpuHasFeature():
if (qHasHwrng() && (uint(qt_randomdevice_control.loadAcquire()) & SkipHWRNG) == 0)
filled += qRandomCpu(buffer, count);
static inline bool qHasHwrng()
{
return qCpuHasFeature(RDRND);
}
Since qCpuHasFeature() also checks if __RDRND__ was defined, we ignore
the result of checkRdrndWorks().
Users of CPUs without RNG must compile with an -march= flag that doesn't
enable it or must pass -mno-rdrnd to keep the runtime detection code.
Task-number: QTBUG-69423
Task-number: QTBUG-129193
Pick-to: 6.8
Change-Id: Ib7819f80041fe330d033fffda7e7c160141d7dd8
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Diffstat (limited to 'src/corelib/global/qsimd.cpp')
| -rw-r--r-- | src/corelib/global/qsimd.cpp | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/src/corelib/global/qsimd.cpp b/src/corelib/global/qsimd.cpp index b4fff814e6c..6f1e12312f9 100644 --- a/src/corelib/global/qsimd.cpp +++ b/src/corelib/global/qsimd.cpp @@ -747,6 +747,12 @@ static bool checkRdrndWorks() noexcept constexpr qsizetype TestBufferSize = 4; unsigned testBuffer[TestBufferSize] = {}; + // But if the RDRND feature was statically enabled by the compiler, we + // assume that the RNG works. That's because the calls to qRandomCpu() will + // be guarded by qCpuHasFeature(RDRND) and that will be a constant true. + if (_compilerCpuFeatures & CpuFeatureRDRND) + return true; + unsigned *end = qt_random_rdrnd(testBuffer, testBuffer + TestBufferSize); if (end < testBuffer + 3) { // Random generation didn't produce enough data for us to make a |