diff options
Diffstat (limited to 'libs/pbd/fpu.cc')
| -rw-r--r-- | libs/pbd/fpu.cc | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/libs/pbd/fpu.cc b/libs/pbd/fpu.cc index 1018414d9b..7efc63715b 100644 --- a/libs/pbd/fpu.cc +++ b/libs/pbd/fpu.cc @@ -69,6 +69,16 @@ FPU::FPU () char* fxbuf = 0; + /* DAZ wasn't available in the first version of SSE. Since + setting a reserved bit in MXCSR causes a general protection + fault, we need to be able to check the availability of this + feature without causing problems. To do this, one needs to + set up a 512-byte area of memory to save the SSE state to, + using fxsave, and then one needs to inspect bytes 28 through + 31 for the MXCSR_MASK value. If bit 6 is set, DAZ is + supported, otherwise, it isn't. + */ + #ifdef NO_POSIX_MEMALIGN if ((fxbuf = (char *) malloc(512)) == 0) #else |