Rewrite simd128 and wasm support (#620)

* Update representation of `v128`
* Rename everything with new naming convention of underscores and no
  modules/impls
* Remove no longer necessary `wasm_simd128` feature
* Remove `#[target_feature]` attributes (use `#[cfg]` instead)
* Update `assert_instr` tests
* Update some implementations as LLVM has evolved
* Allow some more esoteric syntax in `#[assert_instr]`
* Adjust the safety of APIs where appropriate
* Remove macros in favor of hand-coded implementations
* Comment out the tests for now as there's no known runtime for these
  yet

Author: alexcrichton

ci/run.sh

@@ -60,8 +60,13 @@ case ${TARGET} in
         cargo_test "--release"
         ;;
     wasm32-unknown-unknown*)
-        # export RUSTFLAGS="${RUSTFLAGS} -C target-feature=+simd128"
-        cargo_test "--release --features=wasm_simd128"
+        # There's no node or other runtime which supports the most recent SIMD
+        # proposal, but hopefully that's coming soon! For now just test that we
+        # can codegen with no LLVM faults, and we'll remove `--no-run` at a
+        # later date.
+        export RUSTFLAGS="${RUSTFLAGS} -C target-feature=+simd128"
+        export RUSTFLAGS="${RUSTFLAGS} -Cllvm-args=-wasm-enable-unimplemented-simd"
+        cargo_test "--release --no-run"
         ;;
     *)
         ;;

coresimd/wasm32/mod.rs

@@ -1,16 +1,5 @@
 //! WASM32 intrinsics
 
-#![allow(deprecated)]
-
-#[macro_use]
-#[cfg(all(not(test), feature = "wasm_simd128"))]
-mod simd128;
-
-#[cfg(all(test, feature = "wasm_simd128"))]
-pub mod simd128;
-#[cfg(all(test, feature = "wasm_simd128"))]
-pub use self::simd128::*;
-
 #[cfg(test)]
 use stdsimd_test::assert_instr;
 #[cfg(test)]
@@ -21,6 +10,11 @@ mod atomic;
 #[cfg(any(target_feature = "atomics", dox))]
 pub use self::atomic::*;
 
+#[cfg(any(target_feature = "simd128", dox))]
+mod simd128;
+#[cfg(any(target_feature = "simd128", dox))]
+pub use self::simd128::*;
+
 mod memory;
 pub use self::memory::*;