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#define NOP ({ int x; asm("nop" : "=r"(x)); asm("" : : "r"(x)); }) | |
NOINLINE | |
double calc_mispredict_penalty(void) { | |
i64 n = 1ull << 28; | |
u64 rnglen = (n + 63) / 64; | |
u64 *rng = malloc(rnglen * sizeof(u64)); | |
for (u64 i = 0; i < rnglen; i++) | |
rng[i] = random_u64(); | |
u64 *next = rng; | |
i64 i = n; | |
start_timer(); | |
do { | |
u64 bits = *next++; | |
#pragma unroll(64) | |
for (int k = 0; k < 64; k++) { | |
if (bits & (1ull << k)) { | |
RW(i); | |
NOP; | |
} | |
} | |
RW(i); | |
i -= 64; | |
} while (i >= 0); | |
double secs = stop_timer(); | |
double cycles = secs * cpufreq; | |
double penalty = 2.0 * cycles / n; | |
free(rng); | |
return penalty; | |
} |
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