rustc: Add support for some more x86 SIMD ops

This commit adds compiler support for two basic operations needed for binding
SIMD on x86 platforms:

* First, a `nontemporal_store` intrinsic was added for the `_mm_stream_ps`, seen
  in rust-lang-nursery/stdsimd#114. This was relatively straightforward and is
  quite similar to the volatile store intrinsic.

* Next, and much more intrusively, a new type to the backend was added. The
  `x86_mmx` type is used in LLVM for a 64-bit vector register and is used in
  various intrinsics like `_mm_abs_pi8` as seen in rust-lang-nursery/stdsimd#74.
  This new type was added as a new layout option as well as having support added
  to the trans backend. The type is enabled with the `#[repr(x86_mmx)]`
  attribute which is intended to just be an implementation detail of SIMD in
  Rust.

I'm not 100% certain about how the `x86_mmx` type was added, so any extra eyes
or thoughts on that would be greatly appreciated!

1 files changed, 5 insertions, 0 deletions

diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index 0136273ebc9..f1e51e995c2 100644
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -1387,4 +1387,9 @@ extern "rust-intrinsic" {
     /// # } }
     /// ```
     pub fn align_offset(ptr: *const (), align: usize) -> usize;
+
+    /// Emits a `!nontemporal` store according to LLVM (see their docs).
+    /// Probably will never become stable.
+    #[cfg(not(stage0))]
+    pub fn nontemporal_store<T>(ptr: *mut T, val: T);
 }