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Merge pull request #5964 from bunnei/timing-fix

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common: wall_clock: Fix integer overflow with StandardWallClock.
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bunnei 2021-02-19 19:11:05 -08:00 committed by GitHub
parent 728ee181eb 3acb265c9e
commit def03d4075
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 28 additions and 7 deletions
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20
src/common/uint128.h
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@ -98,4 +98,24 @@ namespace Common {
#endif
}
// This function divides a u128 by a u32 value and produces two u64 values:
// the result of division and the remainder
[[nodiscard]] static inline std::pair<u64, u64> Divide128On32(u128 dividend, u32 divisor) {
u64 remainder = dividend[0] % divisor;
u64 accum = dividend[0] / divisor;
if (dividend[1] == 0)
return {accum, remainder};
// We ignore dividend[1] / divisor as that overflows
const u64 first_segment = (dividend[1] % divisor) << 32;
accum += (first_segment / divisor) << 32;
const u64 second_segment = (first_segment % divisor) << 32;
accum += (second_segment / divisor);
remainder += second_segment % divisor;
if (remainder >= divisor) {
accum++;
remainder -= divisor;
}
return {accum, remainder};
}
} // namespace Common

15
src/common/wall_clock.cpp
View file

@ -20,9 +20,7 @@ using base_time_point = std::chrono::time_point<base_timer>;
class StandardWallClock final : public WallClock {
public:
explicit StandardWallClock(u64 emulated_cpu_frequency_, u64 emulated_clock_frequency_)
: WallClock(emulated_cpu_frequency_, emulated_clock_frequency_, false),
emulated_clock_factor{GetFixedPoint64Factor(emulated_clock_frequency, 1000000000)},
emulated_cpu_factor{GetFixedPoint64Factor(emulated_cpu_frequency, 1000000000)} {
: WallClock(emulated_cpu_frequency_, emulated_clock_frequency_, false) {
start_time = base_timer::now();
}
@ -45,11 +43,16 @@ public:
}
u64 GetClockCycles() override {
return MultiplyHigh(GetTimeNS().count(), emulated_clock_factor);
std::chrono::nanoseconds time_now = GetTimeNS();
const u128 temporary =
Common::Multiply64Into128(time_now.count(), emulated_clock_frequency);
return Common::Divide128On32(temporary, 1000000000).first;
}
u64 GetCPUCycles() override {
return MultiplyHigh(GetTimeNS().count(), emulated_cpu_factor);
std::chrono::nanoseconds time_now = GetTimeNS();
const u128 temporary = Common::Multiply64Into128(time_now.count(), emulated_cpu_frequency);
return Common::Divide128On32(temporary, 1000000000).first;
}
void Pause([[maybe_unused]] bool is_paused) override {
@ -58,8 +61,6 @@ public:
private:
base_time_point start_time;
const u64 emulated_clock_factor;
const u64 emulated_cpu_factor;
};
#ifdef ARCHITECTURE_x86_64