Phil Endecott wrote:
Hi David,
David Daney wrote:
Phil Endecott wrote:
This raises another issue, which is whether there is any way for
code to determine which of the atomic builtins are provided, i.e.
I'd like to write:
#if HAS__sync_lock_test_and_set
.. locking code using __sync_lock_test_and_set
#elseif HAS__sync_something_else
.. locking code using builtins that expand to LDREX and STREX
#else
#warn "no atomic ops, falling back to pthread mutex"
...
#endif
The proper symbol to test would be something like:
__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 or
__GCC_HAVE_SYNC_LOCK_TEST_AND_SET_4 they are automatically set by
GCC when the builtin functions are available.
Really? I don't see anything like that in the output of
gcc -dM -E - < /dev/null|grep -i sync
or
grep -R HAVE_SYNC /usr/include/
on my x86 system, which does have a selection of atomic builtins.
$ /home/daney/gccsvn/mips64-trunk/gcc/xgcc
-B/home/daney/gccsvn/mips64-trunk/gcc/ --version
xgcc (GCC) 4.3.0 20070911 (experimental) [trunk revision 128398]
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ /home/daney/gccsvn/mips64-trunk/gcc/xgcc
-B/home/daney/gccsvn/mips64-trunk/gcc/ -E -dM st.c | grep SYNC
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1
Hmm.
