[SLP] Vectorize for all-constant entries.
This should fix libc++'s iostream initialization SIGBUSing on amd64,
whenever the global cout symbol is not aligned to 16 bytes.
Some further explanation: libc++'s iostream.cpp contains the definitions
of std::cout, std::cerr and so on. These global objects are effectively
declared with an alignment of 8 bytes. When an executable is linked
against libc++.so, it can sometimes get a copy of the global object,
which is then at the same alignment.
However, with clang 3.7.0, the initialization of these global objects
will incorrectly use SSE instructions (e.g. movdqa), whenever the
optimization level is high enough, and SSE is enabled, such as on amd64.
When any of these objects is not aligned to 16 bytes, this will result
in a SIGBUS during iostream initialization. In contrast, clang 3.6.x
and earlier took the 8 byte alignment into consideration, and avoided
SSE for those particular operations.
After bisecting of upstream changes, I found that the above revision
caused the change of this behavior, so I am reverting it now as a
workaround, while a discussion and test case is being prepared for
upstream.
this has many visibility problems fixed, which should help with
compiling certain ports that exercise C++11 mode (i.e. Firefox).
Also, belatedly add the LICENSE.TXT and accompanying CREDITS.TXT files,
which are referred to in all the source files.
MFC after: 1 month
MK_LIBCPLUSPLUS=yes to enable). This is a work-in-progress. It works for
me, but is not guaranteed to work for anyone else and may eat your dog.
To build C++ using libc++, add -stdlib=libc++ to your CXX and LD flags.
Bug reports welcome, bug fixes even more welcome...
Approved by: dim (mentor)
