42 lines
946 B
C
42 lines
946 B
C
#include "printf.h"
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typedef unsigned long long uint64_t;
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typedef unsigned long uint32_t;
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#define MTIME_BASE 0x0200BFF8
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uint64_t read_mtime_atomic() {
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uint32_t upper1, lower, upper2;
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do {
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upper1 = *(uint32_t*)(MTIME_BASE + 4);
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lower = *(uint32_t*)(MTIME_BASE);
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upper2 = *(uint32_t*)(MTIME_BASE + 4);
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} while (upper1 != upper2); // Repeat if upper changed during the process
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return ((uint64_t)upper1 << 32) | lower;
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}
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uint32_t timediff_ms(uint64_t start, uint64_t end) {
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uint64_t total = end-start;
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// Clock rate is currently 1MHz
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return (uint32_t)total / 1000;
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}
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int fib(int n) {
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if (n == 0 || n == 1)
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return 1;
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return fib(n-1) + fib(n-2);
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}
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int main() {
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int n = 24;
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uint64_t start = read_mtime_atomic();
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int res = fib(n);
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uint64_t end = read_mtime_atomic();
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uint32_t total_msec = timediff_ms(start, end);
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printf("fib(%d) = %d\n", n, res);
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printf("time: %dms\n", total_msec);
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return 0;
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}
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