[clang] [llvm] [hlsl][dxil][spirv] Add `fma` function (PR #185304)

[Farzon Lotfi via llvm-commits]

================
@@ -1940,6 +1891,22 @@ float3 pow(float3, float3);
 _HLSL_BUILTIN_ALIAS(__builtin_elementwise_pow)
 float4 pow(float4, float4);
 
+//===----------------------------------------------------------------------===//
+// fused multiply-add builtins
+//===----------------------------------------------------------------------===//
+
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_fma)
----------------
farzonl wrote:

```suggestion
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_fma)
```

https://github.com/llvm/llvm-project/pull/185304