[PATCH v2] Add bit operations util header

Add a utility header for simple bit operatios - bitops.h.

At present, just contains the fls() (find last set bit) function.

Signed-off-by: Jeremy Kerr <jk(at)ozlabs(dot)org>

---
v2: only use inline asm with gcc

---
src/include/utils/bitops.h | 53 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)

diff --git a/src/include/utils/bitops.h b/src/include/utils/bitops.h
new file mode 100644
index 0000000..4f2bbc9
--- /dev/null
+++ b/src/include/utils/bitops.h
@@ -0,0 +1,53 @@
+/*-------------------------------------------------------------------------
+ *
+ * bitops.h
+ * Simple bit operations.
+ *
+ * Portions Copyright (c) 2009, PostgreSQL Global Development Group
+ *
+ * $PostgreSQL$
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef BITOPS_H
+#define BITOPS_H
+
+#if defined(__GNUC__) && \
+ (defined(__ppc__) || defined(__powerpc__) || \
+ defined(__ppc64__) || defined (__powerpc64__))
+
+static inline int
+fls(unsigned int x)
+{
+ int lz;
+ asm("cntlz %0,%1" : "=r" (lz) : "r" (x));
+ return 32 - lz;
+}
+
+#else /* !(gcc && powerpc) */
+
+/* Architecture-independent implementations */
+
+/*
+ * fls: find last set bit.
+ *
+ * Returns the 1-based index of the most-significant bit in x. The MSB
+ * is bit number 32, the LSB is bit number 1. If x is zero, returns zero.
+ */
+static inline int
+fls(unsigned int x)
+{
+ int ls = 0;
+
+ while (x != 0)
+ {
+ ls++;
+ x >>= 1;
+ }
+
+ return ls;
+}
+
+#endif
+
+#endif /* BITOPS_H */