Remove duplicate mul_add, keep only mul_sub

StdFloat already provides mul_add. This PR now only adds mul_sub.

Author: GrigoryEvko

crates/core_simd/examples/dot_product.rs

@@ -4,6 +4,7 @@
 // Add these imports to use the stdsimd library
 #![feature(portable_simd)]
 use core_simd::simd::prelude::*;
+use std_float::StdFloat;
 
 // This is your barebones dot product implementation:
 // Take 2 vectors, multiply them element wise and *then*

crates/core_simd/examples/fma.rs

@@ -2,6 +2,7 @@
 
 #![feature(portable_simd)]
 use core_simd::simd::prelude::*;
+use std_float::StdFloat;
 
 fn main() {
     let a = f32x4::from_array([1.0, 2.0, 3.0, 4.0]);

crates/core_simd/src/simd/num/float.rs

@@ -235,27 +235,6 @@ pub trait SimdFloat: Copy + Sealed {
     /// assert!(v.reduce_min().is_nan());
     /// ```
     fn reduce_min(self) -> Self::Scalar;
-
-    /// Fused multiply-add: computes `(self * a) + b` with only one rounding error.
-    ///
-    /// This produces more accurate results than separate multiply and add operations,
-    /// and can be faster on platforms with dedicated FMA instructions.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// # #![feature(portable_simd)]
-    /// # #[cfg(feature = "as_crate")] use core_simd::simd;
-    /// # #[cfg(not(feature = "as_crate"))] use core::simd;
-    /// # use simd::prelude::*;
-    /// let a = f32x4::splat(2.0);
-    /// let b = f32x4::splat(3.0);
-    /// let c = f32x4::splat(4.0);
-    /// assert_eq!(a.mul_add(b, c), f32x4::splat(10.0)); // 2*3 + 4 = 10
-    /// ```
-    #[must_use = "method returns a new vector and does not mutate the original value"]
-    fn mul_add(self, a: Self, b: Self) -> Self;
-
     /// Fused multiply-subtract: computes `(self * a) - b` with only one rounding error.
     ///
     /// This produces more accurate results than separate multiply and subtract operations,
@@ -480,12 +459,6 @@ macro_rules! impl_trait {
                 unsafe { core::intrinsics::simd::simd_reduce_min(self) }
             }
 
-            #[inline]
-            fn mul_add(self, a: Self, b: Self) -> Self {
-                // Safety: `self`, `a`, and `b` are float vectors
-                unsafe { core::intrinsics::simd::simd_fma(self, a, b) }
-            }
-
             #[inline]
             fn mul_sub(self, a: Self, b: Self) -> Self {
                 // self * a - b = self * a + (-b)

crates/core_simd/tests/fma.rs

@@ -1,6 +1,7 @@
 #![feature(portable_simd)]
 
 use core_simd::simd::prelude::*;
+use std_float::StdFloat;
 
 #[test]
 fn test_mul_add_basic() {