[llvm] [LLVM] Change Intrinsic::ID to encode target and intrinsic index (PR #113576)

[Reid Kleckner via llvm-commits]

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@@ -0,0 +1,59 @@
+//===- llvm/Support/IntrinsicID.h - Intrinsic ID encoding -------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains functions to support intrinsic ID encoding. The
+// Intrinsic::ID enum value is constructed using a target prefix index in bits
+// 23-16 (8-bit) and an intrinsic index (index within the list of intrinsics for
+// tha target) in lower 16 bits. To support Intrinsic::ID 0 being not used, the
+// intrinsic index is encoded as Index + 1 for all targets.
+//
+// This file defines functions that encapsulate this encoding.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_INTRINSIC_ID_H
+#define LLVM_SUPPORT_INTRINSIC_ID_H
+
+#include "llvm/Support/FormatVariadic.h"
+#include <limits>
+#include <optional>
+#include <utility>
+
+namespace llvm::Intrinsic {
+typedef unsigned ID;
+
+inline ID EncodeIntrinsicID(unsigned TargetIndex, unsigned IntrinsicIndex) {
+  assert(IntrinsicIndex < std::numeric_limits<uint16_t>::max());
+  assert(TargetIndex <= std::numeric_limits<uint8_t>::max());
+  return (TargetIndex << 16) | (IntrinsicIndex + 1);
+}
+
+inline std::pair<unsigned, unsigned> DecodeIntrinsicID(ID id) {
+  unsigned IntrinsicIndex = id & 0xFFFF;
+  unsigned TargetIndex = id >> 16;
+  assert(IntrinsicIndex != 0);
+  return {TargetIndex, IntrinsicIndex - 1};
+}
+
+inline std::optional<std::pair<unsigned, unsigned>>
+DecodeIntrinsicIDNoFail(ID id) {
+  unsigned IntrinsicIndex = id & 0xFFFF;
+  unsigned TargetIndex = id >> 16;
+  if (IntrinsicIndex == 0)
+    return std::nullopt;
+  return std::make_pair(TargetIndex, IntrinsicIndex - 1);
+}
+
+inline void PrintIntrinsicIDEncoding(raw_ostream &OS, unsigned TargetIndex,
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rnk wrote:

This appears to only be needed in TableGen. Can we move it there to cut the FormatVariadic.h dep?

https://github.com/llvm/llvm-project/pull/113576