Reapply "[NFC][bugpoint] Namespace cleanup in bugpoint" (#168961) (#169055)

This reverts commit b83e458fe5.

Also undo the use of namespace qualifier for `ReducePassList` as that
seems to cause build failures.

llvm/tools/bugpoint/BugDriver.h

@@ -16,6 +16,7 @@
 #define LLVM_TOOLS_BUGPOINT_BUGDRIVER_H
 
 #include "llvm/IR/ValueMap.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Transforms/Utils/ValueMapper.h"
@@ -41,6 +42,10 @@ extern bool DisableSimplifyCFG;
 ///
 extern bool BugpointIsInterrupted;
 
+/// Command line options used across files.
+extern cl::list<std::string> InputArgv;
+extern cl::opt<std::string> OutputPrefix;
+
 class BugDriver {
   LLVMContext &Context;
   const char *ToolName;            // argv[0] of bugpoint

llvm/tools/bugpoint/ExecutionDriver.cpp

@@ -13,7 +13,6 @@
 
 #include "BugDriver.h"
 #include "ToolRunner.h"
-#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/FileUtilities.h"
 #include "llvm/Support/Program.h"
@@ -102,15 +101,13 @@ static cl::opt<std::string> CustomExecCommand(
 
 // Anything specified after the --args option are taken as arguments to the
 // program being debugged.
-namespace llvm {
-cl::list<std::string> InputArgv("args", cl::Positional,
-                                cl::desc("<program arguments>..."),
-                                cl::PositionalEatsArgs);
+cl::list<std::string> llvm::InputArgv("args", cl::Positional,
+                                      cl::desc("<program arguments>..."),
+                                      cl::PositionalEatsArgs);
 
-cl::opt<std::string>
-    OutputPrefix("output-prefix", cl::init("bugpoint"),
-                 cl::desc("Prefix to use for outputs (default: 'bugpoint')"));
-} // namespace llvm
+cl::opt<std::string> llvm::OutputPrefix(
+    "output-prefix", cl::init("bugpoint"),
+    cl::desc("Prefix to use for outputs (default: 'bugpoint')"));
 
 static cl::list<std::string> ToolArgv("tool-args", cl::Positional,
                                       cl::desc("<tool arguments>..."),

llvm/tools/bugpoint/ExtractFunction.cpp

@@ -36,9 +36,6 @@ using namespace llvm;
 #define DEBUG_TYPE "bugpoint"
 
 bool llvm::DisableSimplifyCFG = false;
-namespace llvm {
-extern cl::opt<std::string> OutputPrefix;
-} // namespace llvm
 
 static cl::opt<bool>
     NoDCE("disable-dce",

llvm/tools/bugpoint/Miscompilation.cpp

@@ -28,11 +28,6 @@
 
 using namespace llvm;
 
-namespace llvm {
-extern cl::opt<std::string> OutputPrefix;
-extern cl::list<std::string> InputArgv;
-} // end namespace llvm
-
 static cl::opt<bool> DisableLoopExtraction(
     "disable-loop-extraction",
     cl::desc("Don't extract loops when searching for miscompilations"),

llvm/tools/bugpoint/OptimizerDriver.cpp

@@ -34,10 +34,6 @@ using namespace llvm;
 
 #define DEBUG_TYPE "bugpoint"
 
-namespace llvm {
-extern cl::opt<std::string> OutputPrefix;
-}
-
 static cl::opt<std::string>
     OptCmd("opt-command", cl::init(""),
            cl::desc("Path to opt. (default: search path "