Support WebAssembly Relaxed SIMD

This makes use of the [WebAssembly Relaxed SIMD](https://github.com/WebAssembly/relaxed-simd) instructions, trade off consistent results across architectures for certain edge cases to gain better performance. These differing edge case behaviors already exist in the native equivalents that are used in the SIMD implementation, so this does not regress any correctness.
linebender · Sep 5, 2024 · 5f6ccfc · 5f6ccfc
1 parent 6b4e8c7
commit 5f6ccfc
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Showing 6 changed files with 35 additions and 12 deletions.
diff --git a/.cargo/config.toml b/.cargo/config.toml
@@ -1,2 +1,2 @@
-[target.wasm32-wasi]
+[target.wasm32-wasip1]
 runner = "wasmtime run --dir ."
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
@@ -66,23 +66,28 @@ jobs:
       uses: dtolnay/rust-toolchain@master
       with:
         toolchain: stable
-        target: wasm32-wasi
+        target: wasm32-wasip1
 
     - name: Install wasmtime
       run: |
         curl https://wasmtime.dev/install.sh -sSf | bash
         echo "$HOME/.wasmtime/bin" >> $GITHUB_PATH
 
     - name: Build with minimal features (no_std)
-      run: cargo build --target wasm32-wasi --verbose --no-default-features --features no-std-float
+      run: cargo build --target wasm32-wasip1 --verbose --no-default-features --features no-std-float
 
     - name: Run tests without SIMD
-      run: cargo test --target wasm32-wasi --verbose --no-default-features --features png-format
+      run: cargo test --target wasm32-wasip1 --verbose --no-default-features --features png-format
 
     - name: Run tests with SIMD128
       env:
         RUSTFLAGS: -Ctarget-feature=+simd128,+bulk-memory,+nontrapping-fptoint,+sign-ext
-      run: cargo test --target wasm32-wasi
+      run: cargo test --target wasm32-wasip1
+
+    - name: Run tests with Relaxed SIMD
+      env:
+        RUSTFLAGS: -Ctarget-feature=+simd128,+relaxed-simd,+bulk-memory,+nontrapping-fptoint,+sign-ext
+      run: cargo test --target wasm32-wasip1
 
   aarch64:
     runs-on: ubuntu-20.04

diff --git a/Cargo.toml b/Cargo.toml
@@ -31,8 +31,8 @@ default = ["std", "simd", "png-format"]
 std = ["tiny-skia-path/std"]
 no-std-float = ["tiny-skia-path/no-std-float"]
 
-# Enables SIMD instructions on x86 (from SSE up to AVX2), WebAssembly (SIMD128)
-# and AArch64 (Neon).
+# Enables SIMD instructions on x86 (from SSE up to AVX2), WebAssembly (SIMD128,
+# Relaxed SIMD) and AArch64 (Neon).
 # Has no effect on other targets. Present mainly for testing.
 simd = []
 

diff --git a/src/wide/f32x4_t.rs b/src/wide/f32x4_t.rs
@@ -90,6 +90,8 @@ impl f32x4 {
         cfg_if::cfg_if! {
             if #[cfg(all(feature = "simd", target_feature = "sse2"))] {
                 Self(unsafe { _mm_max_ps(self.0, rhs.0) })
+            } else if #[cfg(all(feature = "simd", target_feature = "relaxed-simd"))] {
+                Self(f32x4_relaxed_max(self.0, rhs.0))
             } else if #[cfg(all(feature = "simd", target_feature = "simd128"))] {
                 Self(f32x4_pmax(self.0, rhs.0))
             } else if #[cfg(all(feature = "simd", target_arch = "aarch64", target_feature = "neon"))] {
@@ -111,6 +113,8 @@ impl f32x4 {
         cfg_if::cfg_if! {
             if #[cfg(all(feature = "simd", target_feature = "sse2"))] {
                 Self(unsafe { _mm_min_ps(self.0, rhs.0) })
+            }  else if #[cfg(all(feature = "simd", target_feature = "relaxed-simd"))] {
+                Self(f32x4_relaxed_min(self.0, rhs.0))
             } else if #[cfg(all(feature = "simd", target_feature = "simd128"))] {
                 Self(f32x4_pmin(self.0, rhs.0))
             } else if #[cfg(all(feature = "simd", target_arch = "aarch64", target_feature = "neon"))] {
@@ -245,6 +249,8 @@ impl f32x4 {
         cfg_if::cfg_if! {
             if #[cfg(all(feature = "simd", target_feature = "sse4.1"))] {
                 Self(unsafe { _mm_blendv_ps(f.0, t.0, self.0) })
+            } else if #[cfg(all(feature = "simd", target_feature = "relaxed-simd"))] {
+                Self(i32x4_relaxed_laneselect(t.0, f.0, self.0))
             } else if #[cfg(all(feature = "simd", target_feature = "simd128"))] {
                 Self(v128_bitselect(t.0, f.0, self.0))
             } else if #[cfg(all(feature = "simd", target_arch = "aarch64", target_feature = "neon"))] {
@@ -302,6 +308,8 @@ impl f32x4 {
         cfg_if::cfg_if! {
             if #[cfg(all(feature = "simd", target_feature = "sse2"))] {
                 i32x4(unsafe { _mm_cvtps_epi32(self.0) })
+            } else if #[cfg(all(feature = "simd", target_feature = "relaxed-simd"))] {
+                i32x4(i32x4_relaxed_trunc_f32x4(self.round().0))
             } else if #[cfg(all(feature = "simd", target_feature = "simd128"))] {
                 i32x4(i32x4_trunc_sat_f32x4(self.round().0))
             } else if #[cfg(all(feature = "simd", target_arch = "aarch64", target_feature = "neon"))] {
@@ -325,6 +333,8 @@ impl f32x4 {
         cfg_if::cfg_if! {
             if #[cfg(all(feature = "simd", target_feature = "sse2"))] {
                 i32x4(unsafe { _mm_cvttps_epi32(self.0) })
+            } else if #[cfg(all(feature = "simd", target_feature = "relaxed-simd"))] {
+                i32x4(i32x4_relaxed_trunc_f32x4(self.0))
             } else if #[cfg(all(feature = "simd", target_feature = "simd128"))] {
                 i32x4(i32x4_trunc_sat_f32x4(self.0))
             } else if #[cfg(all(feature = "simd", target_arch = "aarch64", target_feature = "neon"))] {

diff --git a/src/wide/f32x8_t.rs b/src/wide/f32x8_t.rs
@@ -43,11 +43,17 @@ impl f32x8 {
     }
 
     pub fn floor(self) -> Self {
-        let roundtrip: f32x8 = cast(self.trunc_int().to_f32x8());
-        roundtrip
-            - roundtrip
-                .cmp_gt(self)
-                .blend(f32x8::splat(1.0), f32x8::default())
+        cfg_if::cfg_if! {
+            if #[cfg(all(feature = "simd", target_feature = "simd128"))] {
+                Self(self.0.floor(), self.1.floor())
+            } else {
+                let roundtrip: f32x8 = cast(self.trunc_int().to_f32x8());
+                roundtrip
+                    - roundtrip
+                        .cmp_gt(self)
+                        .blend(f32x8::splat(1.0), f32x8::default())
+            }
+        }
     }
 
     pub fn fract(self) -> Self {

diff --git a/src/wide/i32x4_t.rs b/src/wide/i32x4_t.rs
@@ -56,6 +56,8 @@ impl i32x4 {
         cfg_if::cfg_if! {
             if #[cfg(all(feature = "simd", target_feature = "sse4.1"))] {
                 Self(unsafe { _mm_blendv_epi8(f.0, t.0, self.0) })
+            } else if #[cfg(all(feature = "simd", target_feature = "relaxed-simd"))] {
+                Self(i32x4_relaxed_laneselect(t.0, f.0, self.0))
             } else if #[cfg(all(feature = "simd", target_feature = "simd128"))] {
                 Self(v128_bitselect(t.0, f.0, self.0))
             } else if #[cfg(all(feature = "simd", target_arch = "aarch64", target_feature = "neon"))] {