[NFC][LLVM][CodeGen] Create header file for MIRFSDiscriminator options (llvm#163438)

Extract extern variable declaration into a header per
https://discourse.llvm.org/t/rfc-cs-changes-for-standalone-variables/88581

Author: jurahul

llvm/include/llvm/CodeGen/MIRFSDiscriminatorOptions.h

@@ -0,0 +1,22 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Command line options for MIR Flow Sensitive discriminators.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_MIRFSDISCRIMINATOR_OPTIONS_H
+#define LLVM_CODEGEN_MIRFSDISCRIMINATOR_OPTIONS_H
+
+#include "llvm/Support/CommandLine.h"
+
+namespace llvm {
+extern cl::opt<bool> ImprovedFSDiscriminator;
+} // namespace llvm
+
+#endif // LLVM_CODEGEN_MIRFSDISCRIMINATOR_OPTIONS_H

llvm/lib/CodeGen/MIRFSDiscriminator.cpp

@@ -15,6 +15,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
+#include "llvm/CodeGen/MIRFSDiscriminatorOptions.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/Function.h"
@@ -35,13 +36,10 @@ using namespace sampleprofutil;
 
 // TODO(xur): Remove this option and related code once we make true as the
 // default.
-namespace llvm {
-cl::opt<bool> ImprovedFSDiscriminator(
+cl::opt<bool> llvm::ImprovedFSDiscriminator(
     "improved-fs-discriminator", cl::Hidden, cl::init(false),
     cl::desc("New FS discriminators encoding (incompatible with the original "
              "encoding)"));
-} // namespace llvm
-
 char MIRAddFSDiscriminators::ID = 0;
 
 INITIALIZE_PASS(MIRAddFSDiscriminators, DEBUG_TYPE,

llvm/lib/CodeGen/MIRSampleProfile.cpp

@@ -15,6 +15,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
+#include "llvm/CodeGen/MIRFSDiscriminatorOptions.h"
 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
 #include "llvm/CodeGen/MachineDominators.h"
@@ -62,9 +63,6 @@ static cl::opt<bool> ViewBFIAfter("fs-viewbfi-after", cl::Hidden,
                                   cl::init(false),
                                   cl::desc("View BFI after MIR loader"));
 
-namespace llvm {
-extern cl::opt<bool> ImprovedFSDiscriminator;
-}
 char MIRProfileLoaderPass::ID = 0;
 
 INITIALIZE_PASS_BEGIN(MIRProfileLoaderPass, DEBUG_TYPE,