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Added "int ceil_log2(int)" function

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This commit is contained in:
Clifford Wolf 2016-02-13 16:52:16 +01:00
parent a75f94ec4a
commit 0d7fd2585e
5 changed files with 58 additions and 10 deletions
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25
kernel/yosys.cc
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@ -124,6 +124,31 @@ void yosys_banner()
log("\n");
}
int ceil_log2(int x)
{
if (x <= 0)
return 0;
int y = (x & (x - 1));
y = (y | -y) >> 31;
x |= (x >> 1);
x |= (x >> 2);
x |= (x >> 4);
x |= (x >> 8);
x |= (x >> 16);
x >>= 1;
x -= ((x >> 1) & 0x55555555);
x = (((x >> 2) & 0x33333333) + (x & 0x33333333));
x = (((x >> 4) + x) & 0x0f0f0f0f);
x += (x >> 8);
x += (x >> 16);
x = x & 0x0000003f;
return x - y;
}
std::string stringf(const char *fmt, ...)
{
std::string string;