http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53024
Bug #: 53024 Summary: Power of 2 requirement on vector_size not documented Classification: Unclassified Product: gcc Version: 4.8.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassig...@gcc.gnu.org ReportedBy: marc.gli...@normalesup.org Hello, typedef float VEC __attribute__ ((__vector_size__ (12))); fails to compile with the message: error: number of components of the vector not a power of two This is quite clear, and I guess it makes sense. However, http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html says: "Specifying a combination that is not valid for the current architecture will cause GCC to synthesize the instructions using a narrower mode." so I was expecting gcc to handle it somehow. Could we add a sentence, anywhere in that page, that makes the requirement that the size is a power of 2 explicit? Or if the requirement can be lifted... (I don't care so much about 3 float, I can just store 4 and ignore the last, but I do care about 12 double and don't want to store 16 until we get 512bit vectors)