Rollup merge of rust-lang#133395 - calebzulawski:simd_relaxed_fma, r=…

…workingjubilee

Add simd_relaxed_fma intrinsic

Adds compiler support for rust-lang/portable-simd#387 (comment)

r? `@workingjubilee`

cc `@RalfJung` is this kind of nondeterminism a problem for miri/opsem?

src/intrinsics/simd.rs

@@ -415,7 +415,8 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
             });
         }
 
-        sym::simd_fma => {
+        // FIXME: simd_relaxed_fma doesn't relax to non-fused multiply-add
+        sym::simd_fma | sym::simd_relaxed_fma => {
             intrinsic_args!(fx, args => (a, b, c); intrinsic);
 
             if !a.layout().ty.is_simd() {