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Optimize ceil_log2 function

This commit is contained in:
Matthew Daiter 2019-05-06 18:33:56 -05:00
parent 752553d8e9
commit bafbb9ee90
2 changed files with 5 additions and 3 deletions
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6
kernel/yosys.cc
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@ -151,14 +151,16 @@ void yosys_banner()
int ceil_log2(int x) int ceil_log2(int x)
{ {
#if defined(__GNUC__)
return x > 1 ? (8*sizeof(int)) - __builtin_clz(x-1) : 0;
#else
if (x <= 0) if (x <= 0)
return 0; return 0;
for (int i = 0; i < 32; i++) for (int i = 0; i < 32; i++)
if (((x-1) >> i) == 0) if (((x-1) >> i) == 0)
return i; return i;
log_abort(); log_abort();
#endif
} }
std::string stringf(const char *fmt, ...) std::string stringf(const char *fmt, ...)

2
kernel/yosys.h
View File

@ -244,7 +244,7 @@ extern bool memhasher_active;
inline void memhasher() { if (memhasher_active) memhasher_do(); } inline void memhasher() { if (memhasher_active) memhasher_do(); }
void yosys_banner(); void yosys_banner();
int ceil_log2(int x); int ceil_log2(int x) YS_ATTRIBUTE(const);
std::string stringf(const char *fmt, ...) YS_ATTRIBUTE(format(printf, 1, 2)); std::string stringf(const char *fmt, ...) YS_ATTRIBUTE(format(printf, 1, 2));
std::string vstringf(const char *fmt, va_list ap); std::string vstringf(const char *fmt, va_list ap);
int readsome(std::istream &f, char *s, int n); int readsome(std::istream &f, char *s, int n);