Rely on libm for a no_std alternative to round_ties_even

Update comments around `no_std` CI task

Author: bushrat011899

.github/workflows/ci.yml

@@ -292,7 +292,7 @@ jobs:
           cargo clippy --target ${{ matrix.target }} ${{ matrix.extra-flags }} -p wgpu-hal --all-features
           cargo clippy --target ${{ matrix.target }} ${{ matrix.extra-flags }} -p wgpu --all-features
 
-      # Building for no_std platforms where every feature is enabled except "std".
+      # Building for no_std platforms.
       - name: Check `no_std`
         if: matrix.kind == 'no_std'
         shell: bash
@@ -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".
+          # Check with all compatible features
           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)

Cargo.lock

@@ -91,6 +91,7 @@ hashbrown.workspace = true
 half = { workspace = true, default-features = false, features = ["num-traits"] }
 rustc-hash.workspace = true
 indexmap.workspace = true
+libm = { version = "0.2", default-features = false }
 log.workspace = true
 # `half` requires 0.2.16 for `FromBytes` and `ToBytes`.
 num-traits = { version = "0.2.16", default-features = false }

naga/Cargo.toml

@@ -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/back/mod.rs

@@ -1172,8 +1172,8 @@ impl<'a> ConstantEvaluator<'a> {
             }
             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::Abstract([e]) => Ok(Float::Abstract([libm::rint(e)])),
+                    Float::F32([e]) => Ok(Float::F32([libm::rintf(e)])),
                     Float::F16([e]) => {
                         // TODO: `round_ties_even` is not available on `half::f16` yet.
                         //