__builtin_assume_aligned is not portable, breaking IBM XL

I tried the IBM XL compilers on Summit, now that PGI support has been merged.
I hit the following:

/autofs/nccs-svm1_home1/hargrove/upcxx/.nobs/art/2962a4074e7b6322fe5e6784d65e5fabfd0e55f7/upcxx/utility.hpp:77:17: error: 1540-2993 The builtin "__builtin_assume_aligned" is not supported.
    std::memcpy(__builtin_assume_aligned(dst, align),
                ^

That appears to be the only problem preventing at least rudimentary support for IBM's compilers!

I apply the following change (Yes, I know it defeats the purpose of the function):

--- a/src/utility.hpp
+++ b/src/utility.hpp
@@ -74,8 +74,8 @@ namespace detail {

   template<std::size_t align>
   inline void memcpy_aligned(void *dst, void const *src, std::size_t sz) noexcept {
-    std::memcpy(__builtin_assume_aligned(dst, align),
-                __builtin_assume_aligned(src, align), sz);
+    std::memcpy(dst,
+                src, sz);
   }

   //////////////////////////////////////////////////////////////////////////////

Then the following works on Summit!

$ module load xl/16.1.1-1
$ export CC='xlc -F/ccs/home/hargrove/xlc.cfg.gcc.6.4.0'
$ export CXX='xlC -F/ccs/home/hargrove/xlc.cfg.gcc.6.4.0'
$ UPCXX_INSTALL_NOCHECK=1 ./install inst-xlc
[... lots of unknown Pragma warnings ...]
UPC++ successfully installed

I've not attempted to build or run any tests with the XL compilers, but that's not really the point of this issue.

Comments (5)