feat(const_eval): impl. fma

CHANGELOG.md

@@ -75,6 +75,7 @@ Bottom level categories:
         - `exp`
         - `exp2`
         - `floor`
+        - `fma`
 - Eager release of GPU resources comes from device.trackers. By @bradwerth in [#5075](https://github.com/gfx-rs/wgpu/pull/5075)
 - `wgpu-types`'s `trace` and `replay` features have been replaced by the `serde` feature. By @KirmesBude in [#5149](https://github.com/gfx-rs/wgpu/pull/5149)
 - `wgpu-core`'s `serial-pass` feature has been removed. Use `serde` instead. By @KirmesBude in [#5149](https://github.com/gfx-rs/wgpu/pull/5149)

naga/src/proc/constant_evaluator.rs

@@ -916,6 +916,14 @@ impl<'a> ConstantEvaluator<'a> {
             crate::MathFunction::Floor => {
                 component_wise_float!(self, span, [arg], |e| { Ok([e.floor()]) })
             }
+            crate::MathFunction::Fma => {
+                component_wise_float!(
+                    self,
+                    span,
+                    [arg, arg1.unwrap(), arg2.unwrap()],
+                    |e1, e2, e3| { Ok([e1.mul_add(e2, e3)]) }
+                )
+            }
             crate::MathFunction::Round => {
                 // TODO: Use `f{32,64}.round_ties_even()` when available on stable. This polyfill
                 // is shamelessly [~~stolen from~~ inspired by `ndarray-image`][polyfill source],