Add "algebraic" versions of the fast-math intrinsics

Author: saethlin

core/src/intrinsics.rs

@@ -1882,6 +1882,46 @@ extern "rust-intrinsic" {
     #[rustc_nounwind]
     pub fn frem_fast<T: Copy>(a: T, b: T) -> T;
 
+    /// Float addition that allows optimizations based on algebraic rules.
+    ///
+    /// This intrinsic does not have a stable counterpart.
+    #[rustc_nounwind]
+    #[rustc_safe_intrinsic]
+    #[cfg(not(bootstrap))]
+    pub fn fadd_algebraic<T: Copy>(a: T, b: T) -> T;
+
+    /// Float subtraction that allows optimizations based on algebraic rules.
+    ///
+    /// This intrinsic does not have a stable counterpart.
+    #[rustc_nounwind]
+    #[rustc_safe_intrinsic]
+    #[cfg(not(bootstrap))]
+    pub fn fsub_algebraic<T: Copy>(a: T, b: T) -> T;
+
+    /// Float multiplication that allows optimizations based on algebraic rules.
+    ///
+    /// This intrinsic does not have a stable counterpart.
+    #[rustc_nounwind]
+    #[rustc_safe_intrinsic]
+    #[cfg(not(bootstrap))]
+    pub fn fmul_algebraic<T: Copy>(a: T, b: T) -> T;
+
+    /// Float division that allows optimizations based on algebraic rules.
+    ///
+    /// This intrinsic does not have a stable counterpart.
+    #[rustc_nounwind]
+    #[rustc_safe_intrinsic]
+    #[cfg(not(bootstrap))]
+    pub fn fdiv_algebraic<T: Copy>(a: T, b: T) -> T;
+
+    /// Float remainder that allows optimizations based on algebraic rules.
+    ///
+    /// This intrinsic does not have a stable counterpart.
+    #[rustc_nounwind]
+    #[rustc_safe_intrinsic]
+    #[cfg(not(bootstrap))]
+    pub fn frem_algebraic<T: Copy>(a: T, b: T) -> T;
+
     /// Convert with LLVM’s fptoui/fptosi, which may return undef for values out of range
     /// (<https://github.com/rust-lang/rust/issues/10184>)
     ///