[LiveDebugValues] Install an implementation-picking LiveDebugValues pass

This patch renames the current LiveDebugValues class to "VarLocBasedLDV"
and removes the pass-registration code from it. It creates a separate
LiveDebugValues class that deals with pass registration and management,
that calls through to VarLocBasedLDV::ExtendRanges when
runOnMachineFunction is called. This is done through the "LDVImpl"
abstract class, so that a future patch can install the new
instruction-referencing LiveDebugValues implementation and have it
picked at runtime.

No functional change is intended, just shuffling responsibilities.

Differential Revision: https://reviews.llvm.org/D83046

Author: jmorse

llvm/lib/CodeGen/CMakeLists.txt

@@ -182,6 +182,7 @@ add_llvm_component_library(LLVMCodeGen
   WinEHPrepare.cpp
   XRayInstrumentation.cpp
 
+  LiveDebugValues/LiveDebugValues.cpp
   LiveDebugValues/VarLocBasedImpl.cpp
 
   ADDITIONAL_HEADER_DIRS

llvm/lib/CodeGen/LiveDebugValues/LiveDebugValues.cpp

@@ -0,0 +1,78 @@
+//===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "LiveDebugValues.h"
+
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+
+/// \file LiveDebugValues.cpp
+///
+/// The LiveDebugValues pass extends the range of variable locations
+/// (specified by DBG_VALUE instructions) from single blocks to successors
+/// and any other code locations where the variable location is valid.
+/// There are currently two implementations: the "VarLoc" implementation
+/// explicitly tracks the location of a variable, while the "InstrRef"
+/// implementation tracks the values defined by instructions through locations.
+///
+/// This file implements neither; it merely registers the pass, allows the
+/// user to pick which implementation will be used to propagate variable
+/// locations.
+
+#define DEBUG_TYPE "livedebugvalues"
+
+using namespace llvm;
+
+/// Generic LiveDebugValues pass. Calls through to VarLocBasedLDV or
+/// InstrRefBasedLDV to perform location propagation, via the LDVImpl
+/// base class.
+class LiveDebugValues : public MachineFunctionPass {
+public:
+  static char ID;
+
+  LiveDebugValues();
+  ~LiveDebugValues() { delete TheImpl; }
+
+  /// Calculate the liveness information for the given machine function.
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  MachineFunctionProperties getRequiredProperties() const override {
+    return MachineFunctionProperties().set(
+        MachineFunctionProperties::Property::NoVRegs);
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+private:
+  LDVImpl *TheImpl;
+};
+
+char LiveDebugValues::ID = 0;
+
+char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
+
+INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis", false,
+                false)
+
+/// Default construct and initialize the pass.
+LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
+  initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
+  TheImpl = llvm::makeVarLocBasedLiveDebugValues();
+}
+
+bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
+  auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
+  return TheImpl->ExtendRanges(MF, TPC);
+}

llvm/lib/CodeGen/LiveDebugValues/LiveDebugValues.h

@@ -0,0 +1,31 @@
+//===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/TargetPassConfig.h"
+
+namespace llvm {
+
+// Inline namespace for types / symbols shared between different
+// LiveDebugValues implementations.
+inline namespace SharedLiveDebugValues {
+
+// Expose a base class for LiveDebugValues interfaces to inherit from. This
+// allows the generic LiveDebugValues pass handles to call into the
+// implementation.
+class LDVImpl {
+public:
+  virtual bool ExtendRanges(MachineFunction &MF, TargetPassConfig *TPC) = 0;
+  virtual ~LDVImpl() {}
+};
+
+} // namespace SharedLiveDebugValues
+
+// Factory functions for LiveDebugValues implementations.
+extern LDVImpl *makeVarLocBasedLiveDebugValues();
+} // namespace llvm