Re: [HACKERS] [PATCH v2] Add bit operations util header
* Jeremy Kerr: +#if defined(__GNUC__) \ + (defined(__ppc__) || defined(__powerpc__) || \ + defined(__ppc64__) || defined (__powerpc64__)) If you require GCC anyway, you can use __builtin_clz instead. (It's been available since GCC 4.1 at least.) -- Florian Weimerfwei...@bfk.de BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99 -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] [PATCH v2] Add bit operations util header
Florian, +#if defined(__GNUC__) \ + (defined(__ppc__) || defined(__powerpc__) || \ +defined(__ppc64__) || defined (__powerpc64__)) If you require GCC anyway, you can use __builtin_clz instead. (It's been available since GCC 4.1 at least.) Because now we have to test the compiler *and* the version as well? But I do agree that using the builtins makes for much better code; I'm looking at a future change that does this. Cheers, Jeremy -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] [PATCH v2] Add bit operations util header
* Jeremy Kerr: Florian, +#if defined(__GNUC__) \ + (defined(__ppc__) || defined(__powerpc__) || \ + defined(__ppc64__) || defined (__powerpc64__)) If you require GCC anyway, you can use __builtin_clz instead. (It's been available since GCC 4.1 at least.) Because now we have to test the compiler *and* the version as well? This builtin is not architecture-specific, so you'd save the architecture check. -- Florian Weimerfwei...@bfk.de BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99 -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] [PATCH v2] Add bit operations util header
Florian Weimer fwei...@bfk.de writes: * Jeremy Kerr: Because now we have to test the compiler *and* the version as well? This builtin is not architecture-specific, so you'd save the architecture check. The appropriate way to handle it would be a configure probe to see if the function is available, thus avoiding any wired-in knowledge about compiler or compiler version *or* architecture. The other thing I didn't like about the patch was the assumption that it's okay to have a static inline function in a header. You can get away with that in gcc but *not* in other compilers. Look at the existing coding patterns for, eg, list_head; then go thou and do likewise. Or, since there's currently no need for the code outside aset.c, forget about putting it in a header and just plop it into aset.c. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] [PATCH v2] Add bit operations util header
Hi Tom, The other thing I didn't like about the patch was the assumption that it's okay to have a static inline function in a header. You can get away with that in gcc but *not* in other compilers. Gee, you user-space guys have it tough! :D Point taken, will rework. Look at the existing coding patterns for, eg, list_head; then go thou and do likewise. Or, since there's currently no need for the code outside aset.c, forget about putting it in a header and just plop it into aset.c. OK, I'll add a configure check and conditionally use the builtin if it's available. I have some other patches that could be improved by using other builtins, so it would be a good opportunity to figure out a nice pattern for doing this. Cheers, Jeremy -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
[HACKERS] [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 j...@ozlabs.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 000..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 */
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
