Add no_std polyfill for round_ties_even for f32 and f64, not just f16

Author: bushrat011899

.github/workflows/ci.yml

@@ -301,9 +301,11 @@ jobs:
 
           # check with no features
           cargo clippy --target ${{ matrix.target }} ${{ matrix.extra-flags }} -p wgpu-types --no-default-features
+          cargo clippy --target ${{ matrix.target }} ${{ matrix.extra-flags }} -p naga --no-default-features
 
           # Check with all features except "std".
           cargo clippy --target ${{ matrix.target }} ${{ matrix.extra-flags }} -p wgpu-types --no-default-features --features strict_asserts,fragile-send-sync-non-atomic-wasm,serde,counters
+          cargo clippy --target ${{ matrix.target }} ${{ matrix.extra-flags }} -p naga --no-default-features --features dot-out,compact
 
       # Building for native platforms with standard tests.
       - name: Check native

CHANGELOG.md

@@ -42,6 +42,10 @@ Bottom level categories:
 
 ### New Features
 
+#### Naga
+
+- Added `no_std` support with default features disabled. By @Bushrat011899 in [#7585](https://github.com/gfx-rs/wgpu/pull/7585).
+
 #### General
 
 - Add support for rendering to slices of 3D texture views and single layered 2D-Array texture views (this requires `VK_KHR_maintenance1` which should be widely available on newer drivers). By @teoxoy in [#7596](https://github.com/gfx-rs/wgpu/pull/7596)

naga/src/back/mod.rs

@@ -46,6 +46,13 @@ pub type NeedBakeExpressions = crate::FastHashSet<crate::Handle<crate::Expressio
 ///
 /// [`Expression`]: crate::Expression
 /// [`Handle`]: crate::Handle
+#[cfg_attr(
+    not(any(glsl_out, hlsl_out, msl_out, wgsl_out)),
+    allow(
+        dead_code,
+        reason = "shared helpers can be dead if none of the enabled backends need it"
+    )
+)]
 struct Baked(crate::Handle<crate::Expression>);
 
 impl core::fmt::Display for Baked {

naga/src/proc/constant_evaluator.rs

@@ -1171,34 +1171,46 @@ impl<'a> ConstantEvaluator<'a> {
                 component_wise_float!(self, span, [arg], |e| { Ok([e.floor()]) })
             }
             crate::MathFunction::Round => {
-                component_wise_float(self, span, [arg], |e| match e {
-                    Float::Abstract([e]) => Ok(Float::Abstract([e.round_ties_even()])),
-                    Float::F32([e]) => Ok(Float::F32([e.round_ties_even()])),
-                    Float::F16([e]) => {
-                        // TODO: `round_ties_even` is not available on `half::f16` yet.
-                        //
-                        // This polyfill is shamelessly [~~stolen from~~ inspired by `ndarray-image`][polyfill source],
-                        // which has licensing compatible with ours. See also
-                        // <https://github.com/rust-lang/rust/issues/96710>.
-                        //
-                        // [polyfill source]: https://github.com/imeka/ndarray-ndimage/blob/8b14b4d6ecfbc96a8a052f802e342a7049c68d8f/src/lib.rs#L98
-                        fn round_ties_even(x: f64) -> f64 {
-                            let i = x as i64;
-                            let f = (x - i as f64).abs();
-                            if f == 0.5 {
-                                if i & 1 == 1 {
-                                    // -1.5, 1.5, 3.5, ...
-                                    (x.abs() + 0.5).copysign(x)
-                                } else {
-                                    (x.abs() - 0.5).copysign(x)
-                                }
-                            } else {
-                                x.round()
-                            }
-                        }
+                /// Rounds to the nearest integer, with ties biasing towards an even result.
+                ///
+                /// # TODO
+                ///
+                /// - `round_ties_even` is not available on `half::f16` yet.
+                /// - It is also not available on `no_std`
+                ///
+                /// This polyfill is shamelessly [~~stolen from~~ inspired by `ndarray-image`][polyfill source],
+                /// which has licensing compatible with ours. See also
+                /// <https://github.com/rust-lang/rust/issues/96710>.
+                ///
+                /// [polyfill source]: https://github.com/imeka/ndarray-ndimage/blob/8b14b4d6ecfbc96a8a052f802e342a7049c68d8f/src/lib.rs#L98
+                fn round_ties_even<T: num_traits::float::FloatCore>(x: T) -> T {
+                    let half = (T::one() + T::one()).recip();
+
+                    if x.fract().abs() != half {
+                        x.round()
+                    } else {
+                        let i = x.abs().trunc();
 
-                        Ok(Float::F16([(f16::from_f64(round_ties_even(f64::from(e))))]))
+                        let value = if (i * half).fract() == half {
+                            // -1.5, 1.5, 3.5, ...
+                            x.abs() + half
+                        } else {
+                            // -0.5, 0.5, 2.5, ...
+                            x.abs() - half
+                        };
+
+                        if x.signum() != value.signum() {
+                            -value
+                        } else {
+                            value
+                        }
                     }
+                }
+
+                component_wise_float(self, span, [arg], |e| match e {
+                    Float::Abstract([e]) => Ok(Float::Abstract([round_ties_even(e)])),
+                    Float::F32([e]) => Ok(Float::F32([round_ties_even(e)])),
+                    Float::F16([e]) => Ok(Float::F16([round_ties_even(e)])),
                 })
             }
             crate::MathFunction::Fract => {