X-Git-Url: https://git.libre-soc.org/?a=blobdiff_plain;f=kernel%2Fyosys.cc;h=377572fc2984243a2ede59d2e35af34a7fa27b8d;hb=d26646051c4ae9740decd5d76eec6a3afd63844a;hp=20d972150a978239ae96731ef5622b47929a488a;hpb=314ff1e4ca00ef8024bbb0d2f031efd78b01f9a1;p=yosys.git

diff --git a/kernel/yosys.cc b/kernel/yosys.cc
index 20d972150..377572fc2 100644
--- a/kernel/yosys.cc
+++ b/kernel/yosys.cc
@@ -151,14 +151,16 @@ void yosys_banner()
 
 int ceil_log2(int x)
 {
+#if defined(__GNUC__)
+        return x > 1 ? (8*sizeof(int)) - __builtin_clz(x-1) : 0;
+#else
 	if (x <= 0)
 		return 0;
-
 	for (int i = 0; i < 32; i++)
 		if (((x-1) >> i) == 0)
 			return i;
-
 	log_abort();
+#endif
 }
 
 std::string stringf(const char *fmt, ...)