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

…bilee

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/intrinsic/simd.rs

@@ -772,6 +772,7 @@ pub fn generic_simd_intrinsic<'a, 'gcc, 'tcx>(
             sym::simd_flog => "log",
             sym::simd_floor => "floor",
             sym::simd_fma => "fma",
+            sym::simd_relaxed_fma => "fma", // FIXME: this should relax to non-fused multiply-add when necessary
             sym::simd_fpowi => "__builtin_powi",
             sym::simd_fpow => "pow",
             sym::simd_fsin => "sin",