feat: implement dup(2), dup2(2)

[lunaix-os.git] / lunaix-os / includes / lunaix / spike.h

diff --git a/lunaix-os/includes/lunaix/spike.h b/lunaix-os/includes/lunaix/spike.h
index 8297f0e9af5ffc9a9308f1985093b6fea80d8825..4e17993266adbf0e96971a034c39f4517d723cad 100644 (file)
--- a/lunaix-os/includes/lunaix/spike.h
+++ b/lunaix-os/includes/lunaix/spike.h
@@ -20,6 +20,48 @@
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
 #define MAX(a, b) ((a) > (b) ? (a) : (b))
 
+/**
+ * @brief Fast log base 2 for integer, utilizing constant unfolding.
+ * Adopted from
+ * https://elixir.bootlin.com/linux/v4.4/source/include/linux/log2.h#L85
+ *
+ */
+#define ILOG2(x)                                                               \
+    __builtin_constant_p(x) ? ((x) == 0              ? 0                       \
+                               : ((x) & (1ul << 31)) ? 31                      \
+                               : ((x) & (1ul << 30)) ? 30                      \
+                               : ((x) & (1ul << 29)) ? 29                      \
+                               : ((x) & (1ul << 28)) ? 28                      \
+                               : ((x) & (1ul << 27)) ? 27                      \
+                               : ((x) & (1ul << 26)) ? 26                      \
+                               : ((x) & (1ul << 25)) ? 25                      \
+                               : ((x) & (1ul << 24)) ? 24                      \
+                               : ((x) & (1ul << 23)) ? 23                      \
+                               : ((x) & (1ul << 22)) ? 22                      \
+                               : ((x) & (1ul << 21)) ? 21                      \
+                               : ((x) & (1ul << 20)) ? 20                      \
+                               : ((x) & (1ul << 19)) ? 19                      \
+                               : ((x) & (1ul << 18)) ? 18                      \
+                               : ((x) & (1ul << 17)) ? 17                      \
+                               : ((x) & (1ul << 16)) ? 16                      \
+                               : ((x) & (1ul << 15)) ? 15                      \
+                               : ((x) & (1ul << 14)) ? 14                      \
+                               : ((x) & (1ul << 13)) ? 13                      \
+                               : ((x) & (1ul << 12)) ? 12                      \
+                               : ((x) & (1ul << 11)) ? 11                      \
+                               : ((x) & (1ul << 10)) ? 10                      \
+                               : ((x) & (1ul << 9))  ? 9                       \
+                               : ((x) & (1ul << 8))  ? 8                       \
+                               : ((x) & (1ul << 7))  ? 7                       \
+                               : ((x) & (1ul << 6))  ? 6                       \
+                               : ((x) & (1ul << 5))  ? 5                       \
+                               : ((x) & (1ul << 4))  ? 4                       \
+                               : ((x) & (1ul << 3))  ? 3                       \
+                               : ((x) & (1ul << 2))  ? 2                       \
+                               : ((x) & (1ul << 1))  ? 1                       \
+                                                     : 0)                       \
+                            : (31 - __builtin_clz(x))
+
 #define __USER__ __attribute__((section(".usrtext")))
 
 inline static void