1 // ---------------------------------------------------------------------- 2 // CycleClock 3 // A CycleClock tells you the current time in Cycles. The "time" 4 // is actually time since power-on. This is like time() but doesn't 5 // involve a system call and is much more precise. 6 // 7 // NOTE: Not all cpu/platform/kernel combinations guarantee that this 8 // clock increments at a constant rate or is synchronized across all logical 9 // cpus in a system. 10 // 11 // If you need the above guarantees, please consider using a different 12 // API. There are efforts to provide an interface which provides a millisecond 13 // granularity and implemented as a memory read. A memory read is generally 14 // cheaper than the CycleClock for many architectures. 15 // 16 // Also, in some out of order CPU implementations, the CycleClock is not 17 // serializing. So if you're trying to count at cycles granularity, your 18 // data might be inaccurate due to out of order instruction execution. 19 // ---------------------------------------------------------------------- 20 21 #ifndef BENCHMARK_CYCLECLOCK_H_ 22 #define BENCHMARK_CYCLECLOCK_H_ 23 24 #include <cstdint> 25 26 #include "benchmark/benchmark.h" 27 #include "internal_macros.h" 28 29 #if defined(BENCHMARK_OS_MACOSX) 30 #include <mach/mach_time.h> 31 #endif 32 // For MSVC, we want to use '_asm rdtsc' when possible (since it works 33 // with even ancient MSVC compilers), and when not possible the 34 // __rdtsc intrinsic, declared in <intrin.h>. Unfortunately, in some 35 // environments, <windows.h> and <intrin.h> have conflicting 36 // declarations of some other intrinsics, breaking compilation. 37 // Therefore, we simply declare __rdtsc ourselves. See also 38 // http://connect.microsoft.com/VisualStudio/feedback/details/262047 39 #if defined(COMPILER_MSVC) && !defined(_M_IX86) 40 extern "C" uint64_t __rdtsc(); 41 #pragma intrinsic(__rdtsc) 42 #endif 43 44 #if !defined(BENCHMARK_OS_WINDOWS) || defined(BENCHMARK_OS_MINGW) 45 #include <sys/time.h> 46 #include <time.h> 47 #endif 48 49 #ifdef BENCHMARK_OS_EMSCRIPTEN 50 #include <emscripten.h> 51 #endif 52 53 namespace benchmark { 54 // NOTE: only i386 and x86_64 have been well tested. 55 // PPC, sparc, alpha, and ia64 are based on 56 // http://peter.kuscsik.com/wordpress/?p=14 57 // with modifications by m3b. See also 58 // https://setisvn.ssl.berkeley.edu/svn/lib/fftw-3.0.1/kernel/cycle.h 59 namespace cycleclock { 60 // This should return the number of cycles since power-on. Thread-safe. 61 inline BENCHMARK_ALWAYS_INLINE int64_t Now() { 62 #if defined(BENCHMARK_OS_MACOSX) 63 // this goes at the top because we need ALL Macs, regardless of 64 // architecture, to return the number of "mach time units" that 65 // have passed since startup. See sysinfo.cc where 66 // InitializeSystemInfo() sets the supposed cpu clock frequency of 67 // macs to the number of mach time units per second, not actual 68 // CPU clock frequency (which can change in the face of CPU 69 // frequency scaling). Also note that when the Mac sleeps, this 70 // counter pauses; it does not continue counting, nor does it 71 // reset to zero. 72 return mach_absolute_time(); 73 #elif defined(BENCHMARK_OS_EMSCRIPTEN) 74 // this goes above x86-specific code because old versions of Emscripten 75 // define __x86_64__, although they have nothing to do with it. 76 return static_cast<int64_t>(emscripten_get_now() * 1e+6); 77 #elif defined(__i386__) 78 int64_t ret; 79 __asm__ volatile("rdtsc" : "=A"(ret)); 80 return ret; 81 #elif defined(__x86_64__) || defined(__amd64__) 82 uint64_t low, high; 83 __asm__ volatile("rdtsc" : "=a"(low), "=d"(high)); 84 return (high << 32) | low; 85 #elif defined(__powerpc__) || defined(__ppc__) 86 // This returns a time-base, which is not always precisely a cycle-count. 87 #if defined(__powerpc64__) || defined(__ppc64__) 88 int64_t tb; 89 asm volatile("mfspr %0, 268" : "=r"(tb)); 90 return tb; 91 #else 92 uint32_t tbl, tbu0, tbu1; 93 asm volatile( 94 "mftbu %0\n" 95 "mftb %1\n" 96 "mftbu %2" 97 : "=r"(tbu0), "=r"(tbl), "=r"(tbu1)); 98 tbl &= -static_cast<int32_t>(tbu0 == tbu1); 99 // high 32 bits in tbu1; low 32 bits in tbl (tbu0 is no longer needed) 100 return (static_cast<uint64_t>(tbu1) << 32) | tbl; 101 #endif 102 #elif defined(__sparc__) 103 int64_t tick; 104 asm(".byte 0x83, 0x41, 0x00, 0x00"); 105 asm("mov %%g1, %0" : "=r"(tick)); 106 return tick; 107 #elif defined(__ia64__) 108 int64_t itc; 109 asm("mov %0 = ar.itc" : "=r"(itc)); 110 return itc; 111 #elif defined(COMPILER_MSVC) && defined(_M_IX86) 112 // Older MSVC compilers (like 7.x) don't seem to support the 113 // __rdtsc intrinsic properly, so I prefer to use _asm instead 114 // when I know it will work. Otherwise, I'll use __rdtsc and hope 115 // the code is being compiled with a non-ancient compiler. 116 _asm rdtsc 117 #elif defined(COMPILER_MSVC) 118 return __rdtsc(); 119 #elif defined(BENCHMARK_OS_NACL) 120 // Native Client validator on x86/x86-64 allows RDTSC instructions, 121 // and this case is handled above. Native Client validator on ARM 122 // rejects MRC instructions (used in the ARM-specific sequence below), 123 // so we handle it here. Portable Native Client compiles to 124 // architecture-agnostic bytecode, which doesn't provide any 125 // cycle counter access mnemonics. 126 127 // Native Client does not provide any API to access cycle counter. 128 // Use clock_gettime(CLOCK_MONOTONIC, ...) instead of gettimeofday 129 // because is provides nanosecond resolution (which is noticable at 130 // least for PNaCl modules running on x86 Mac & Linux). 131 // Initialize to always return 0 if clock_gettime fails. 132 struct timespec ts = { 0, 0 }; 133 clock_gettime(CLOCK_MONOTONIC, &ts); 134 return static_cast<int64_t>(ts.tv_sec) * 1000000000 + ts.tv_nsec; 135 #elif defined(__aarch64__) 136 // System timer of ARMv8 runs at a different frequency than the CPU's. 137 // The frequency is fixed, typically in the range 1-50MHz. It can be 138 // read at CNTFRQ special register. We assume the OS has set up 139 // the virtual timer properly. 140 int64_t virtual_timer_value; 141 asm volatile("mrs %0, cntvct_el0" : "=r"(virtual_timer_value)); 142 return virtual_timer_value; 143 #elif defined(__ARM_ARCH) 144 // V6 is the earliest arch that has a standard cyclecount 145 // Native Client validator doesn't allow MRC instructions. 146 #if (__ARM_ARCH >= 6) 147 uint32_t pmccntr; 148 uint32_t pmuseren; 149 uint32_t pmcntenset; 150 // Read the user mode perf monitor counter access permissions. 151 asm volatile("mrc p15, 0, %0, c9, c14, 0" : "=r"(pmuseren)); 152 if (pmuseren & 1) { // Allows reading perfmon counters for user mode code. 153 asm volatile("mrc p15, 0, %0, c9, c12, 1" : "=r"(pmcntenset)); 154 if (pmcntenset & 0x80000000ul) { // Is it counting? 155 asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r"(pmccntr)); 156 // The counter is set up to count every 64th cycle 157 return static_cast<int64_t>(pmccntr) * 64; // Should optimize to << 6 158 } 159 } 160 #endif 161 struct timeval tv; 162 gettimeofday(&tv, nullptr); 163 return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec; 164 #elif defined(__mips__) || defined(__m68k__) 165 // mips apparently only allows rdtsc for superusers, so we fall 166 // back to gettimeofday. It's possible clock_gettime would be better. 167 struct timeval tv; 168 gettimeofday(&tv, nullptr); 169 return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec; 170 #elif defined(__s390__) // Covers both s390 and s390x. 171 // Return the CPU clock. 172 uint64_t tsc; 173 asm("stck %0" : "=Q" (tsc) : : "cc"); 174 return tsc; 175 #elif defined(__riscv) // RISC-V 176 // Use RDCYCLE (and RDCYCLEH on riscv32) 177 #if __riscv_xlen == 32 178 uint32_t cycles_lo, cycles_hi0, cycles_hi1; 179 // This asm also includes the PowerPC overflow handling strategy, as above. 180 // Implemented in assembly because Clang insisted on branching. 181 asm volatile( 182 "rdcycleh %0\n" 183 "rdcycle %1\n" 184 "rdcycleh %2\n" 185 "sub %0, %0, %2\n" 186 "seqz %0, %0\n" 187 "sub %0, zero, %0\n" 188 "and %1, %1, %0\n" 189 : "=r"(cycles_hi0), "=r"(cycles_lo), "=r"(cycles_hi1)); 190 return (static_cast<uint64_t>(cycles_hi1) << 32) | cycles_lo; 191 #else 192 uint64_t cycles; 193 asm volatile("rdcycle %0" : "=r"(cycles)); 194 return cycles; 195 #endif 196 #else 197 // The soft failover to a generic implementation is automatic only for ARM. 198 // For other platforms the developer is expected to make an attempt to create 199 // a fast implementation and use generic version if nothing better is available. 200 #error You need to define CycleTimer for your OS and CPU 201 #endif 202 } 203 } // end namespace cycleclock 204 } // end namespace benchmark 205 206 #endif // BENCHMARK_CYCLECLOCK_H_ 207