branches/innodb+ rb://257

When a transaction joins we check if there are any other transactions
waiting on its locks. If there aren't any waiting then no deadlock can
occur.  This patch however has additional changes.

 1. Count leading zeros
 2. Count trailing zeros

There are two version of both these utility functions. One is hand
coded and the other will use the GCC builtin when available. The
changes to configure have yet to be made.

Simplify the next record lock fetch in the deadlock check code.

Pass the heap number as a parameter to the deadlock check code.

Written by: Sunny

include/ut0ut.h

@@ -217,6 +217,22 @@ store the given number of bits.
 @return		number of bytes (octets) needed to represent b */
 #define UT_BITS_IN_BYTES(b) (((b) + 7) / 8)
 
+/*************************************************************//**
+Calculates the leading zeros in a 32 bint unsigned integer
+@return	number of leading zeros or ULINT_UNDEFINED if n == 0 */
+UNIV_INLINE
+ulint
+ut_nlz(
+/*===*/
+	ib_uint32_t	n);	/*!< in: number */
+/*************************************************************//**
+Calculates the trailing zeros in a 32 bint unsigned integer
+@return	number of trailing zeros or ULINT_UNDEFINED if n == 0 */
+UNIV_INLINE
+ulint
+ut_ntz(
+/*===*/
+	ib_uint32_t	n);	/*!< in: number */
 /**********************************************************//**
 Returns system time. We do not specify the format of the time returned:
 the only way to manipulate it is to use the function ut_difftime.

include/ut0ut.ic

@@ -160,3 +160,68 @@ ut_2_exp(
 {
 	return((ulint) 1 << n);
 }
+
+/*************************************************************//**
+@return the number of 1s in a 32 bit uint. */
+UNIV_INLINE
+int
+ut_popcount(
+/*========*/
+	ib_uint32_t	n)
+{
+	n = n - ((n >> 1) & 0x55555555);
+	n = (n & 0x33333333) + ((n >> 2) & 0x33333333);
+	n = (n + (n >> 4)) & 0x0F0F0F0F;
+	n = n + (n << 8);
+	n = n + (n << 16);
+
+	return(n >> 24);
+}
+
+/*************************************************************//**
+Calculates the leading zeros in a 32 bint unsigned integer
+@return	number of leading zeros or ULINT_UNDEFINED if n == 0 */
+UNIV_INLINE
+ulint
+ut_nlz(
+/*===*/
+	ib_uint32_t	n)	/*!< in: number */
+{
+#ifdef HAVE_GCC_CLZ
+	return(__builtin_clz(n));
+#else
+	n |= n >> 1;
+	n |= n >> 2;
+	n |= n >> 4;
+	n |= n >> 8;
+	n |= n >>16;
+
+	return(ut_popcount(~n));
+#endif /* HAVE_GCC_CLZ */
+}
+
+/*************************************************************//**
+Calculates the trailing zeros in a 32 bint unsigned integer
+@return	number of trailing zeros or ULINT_UNDEFINED if n == 0 */
+UNIV_INLINE
+ulint
+ut_ntz(
+/*===*/
+	ib_uint32_t	n)	/*!< in: number */
+{
+#ifdef HAVE_GCC_CTZ
+	return(__builtin_ctzl(n));
+#else
+	ib_uint32_t	y, bz, b4, b3, b2, b1, b0;
+
+	y = n & -n;			/* Isolate rightmost 1-bit. */
+	bz = y ? 0 : 1;			/* 1 if y = 0. */
+	b4 = (y & 0x0000FFFF) ? 0 : 16;
+	b3 = (y & 0x00FF00FF) ? 0 : 8;
+	b2 = (y & 0x0F0F0F0F) ? 0 : 4;
+	b1 = (y & 0x33333333) ? 0 : 2;
+	b0 = (y & 0x55555555) ? 0 : 1;
+
+	return(bz + b4 + b3 + b2 + b1 + b0);
+#endif /* HAVE_GCC_CTZ */
+}