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<chrono>: Cache QueryPerformanceFrequency() #646

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Merged
BillyONeal merged 16 commits into from
Apr 1, 2020
Merged

<chrono>: Cache QueryPerformanceFrequency() #646

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a456502
caching QueryPerformanceFrequency() #448
AlexGuteniev Mar 27, 2020
1cac892
missing static
AlexGuteniev Mar 27, 2020
8ce0267
clang format
AlexGuteniev Mar 27, 2020
244a15b
avoid __iso_volatile_store64
AlexGuteniev Mar 27, 2020
8b1c5c3
Suppress a warning that I'm thinking is false
AlexGuteniev Mar 27, 2020
abbd365
clang format
AlexGuteniev Mar 27, 2020
4250eeb
clang format
AlexGuteniev Mar 27, 2020
8ae738c
Proper place to suppress a warning I'm thinking false
AlexGuteniev Mar 27, 2020
bb746ac
clang format
AlexGuteniev Mar 27, 2020
e1fb775
Move implementation to .cpp
AlexGuteniev Mar 28, 2020
9312817
clang format
AlexGuteniev Mar 28, 2020
44448ef
remove unnecessary function
AlexGuteniev Mar 28, 2020
d6ea49b
Restore old code for _M_CEE_PURE
AlexGuteniev Mar 29, 2020
bc849c9
Merge remote-tracking branch 'origin/master' into chrono_cache_qpf
BillyONeal Mar 31, 2020
f7234f4
Remove unnecessary _M_CEE_PURE guards; xtime.cpp is compiled as nativ…
BillyONeal Mar 31, 2020
f10ced4
Use direct-init.
BillyONeal Mar 31, 2020
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13 changes: 10 additions & 3 deletions stl/src/xtime.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
// xtime functions

#include "awint.h"
#include <atomic>
#include <stdlib.h>
#include <time.h>
#include <xtimec.h>
Expand Down Expand Up @@ -87,9 +88,15 @@ _CRTIMP2_PURE long long __cdecl _Query_perf_counter() { // get current value of
}

_CRTIMP2_PURE long long __cdecl _Query_perf_frequency() { // get frequency of performance counter
LARGE_INTEGER li;
QueryPerformanceFrequency(&li); // always succeeds
return li.QuadPart;
static std::atomic<long long> freq_cached{0};
long long freq = freq_cached.load(std::memory_order_relaxed);
if (freq == 0) {
LARGE_INTEGER li;
QueryPerformanceFrequency(&li); // always succeeds
freq = li.QuadPart; // doesn't change after system boot
freq_cached.store(freq, std::memory_order_relaxed);
}
return freq;
}

_END_EXTERN_C
Expand Down