[libclc] [libclc] Improve performance and precision of reciprocal functions (PR #203805)

[Matt Arsenault via cfe-commits]

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@@ -0,0 +1,16 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// On AMDGPU the "fast" reciprocal is the hardware v_rcp_f32 approximation,
+_CLC_OVERLOAD _CLC_DEF __CLC_GENTYPE __clc_recip_fast(__CLC_GENTYPE x) {
+#if defined(__CLC_SCALAR) && __CLC_FPSIZE == 32
+  return __builtin_amdgcn_rcpf(x);
----------------
arsenm wrote:

I thought I was trying to avoid using this. Don't you get the raw instruction with afn + reciprocal pattern with all denormal modes?

https://github.com/llvm/llvm-project/pull/203805