wasm2c: add SIMD support (#2119)

This change incorporates [simd-everywhere](https://github.com/simd-everywhere/simde) into the wasm2c output, which maps wasm SIMD C intrinsics to any supported target architecture.

Author: wrv

.github/workflows/build.yml

@@ -85,6 +85,7 @@ jobs:
     env:
       USE_NINJA: "1"
       CC: "clang"
+      WASM2C_CFLAGS: "-march=x86-64-v2" # currently required for SIMDe to pass some tests on x86-64
     strategy:
       matrix:
         sanitizer: [asan, ubsan]
@@ -106,7 +107,7 @@ jobs:
     env:
       USE_NINJA: "1"
       CC: "clang" # used by the wasm2c tests
-      WASM2C_CFLAGS: "-fsanitize=address -DWASM_RT_MEMCHECK_SIGNAL_HANDLER=0"
+      WASM2C_CFLAGS: "-march=x86-64-v2 -fsanitize=address -DWASM_RT_MEMCHECK_SIGNAL_HANDLER=0"
     steps:
     - uses: actions/setup-python@v1
       with:

.gitmodules

@@ -16,3 +16,6 @@
 [submodule "third_party/picosha2"]
 	path = third_party/picosha2
 	url = https://github.com/okdshin/PicoSHA2
+[submodule "third_party/simde"]
+	path = third_party/simde
+	url = https://github.com/simd-everywhere/simde

README.md

@@ -51,7 +51,7 @@ Wabt has been compiled to JavaScript via emscripten. Some of the functionality i
 | [mutable globals][]   | `--disable-mutable-globals` | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
 | [nontrapping float-to-int conversions][] | `--disable-saturating-float-to-int` | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
 | [sign extension][]    | `--disable-sign-extension`  | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
-| [simd][]              | `--disable-simd`            | ✓ | ✓ | ✓ | ✓ | ✓ |   |
+| [simd][]              | `--disable-simd`            | ✓ | ✓ | ✓ | ✓ | ✓ | 🚧 |
 | [threads][]           | `--enable-threads`          |   | ✓ | ✓ | ✓ | ✓ |   |
 | [multi-value][]       | `--disable-multi-value`     | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
 | [tail-call][]         | `--enable-tail-call`        |   | ✓ | ✓ | ✓ | ✓ |   |