The `experimental_simd` build target builds
CanvasKit using the Emscripten `-msimd128` flag, to build CanvasKit
with SIMD instructions in the compiled WASM. This build of
CanvasKit works in Chrome Canary 86.0.4186.0
with chrome://flags#enable-webassembly-simd enabled.
Also add WebAssembly-specific intrinsics to SkVx.h to enable
support for almost all native SIMD operations in CanvasKit WebAssmebly.
Also add a Skia/modules/canvaskit/wasm_tools/SIMD folder which contains
build_simd_test.sh for testing whether WASM SIMD intrinsics operations
are actually being used by skvx, and for testing correctness of
WASM SIMD operations. Also contains simd_float_test.cpp and
simd_int_test.cpp which serve as documentation for which operations are
correctly turned into WASM SIMD operations by emscripten.
Bug: skia:10453
Change-Id: Icd312b4d189e8d8667d3ffe12a72bfa6febaab2f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/299705
Reviewed-by: Mike Klein <mtklein@google.com>
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