[NewPM][CodeGen] Introduce CodeGenPassBuilder to help build codegen pipeline

Following up on D67687.
Please refer to the RFC here http://lists.llvm.org/pipermail/llvm-dev/2020-July/143309.html

`CodeGenPassBuilder` is the NPM counterpart of `TargetPassConfig` with below differences.
- Debugging features (MIR print/verify, disable pass, start/stop-before/after, etc.) living in `TargetPassConfig` are moved to use PassInstrument as much as possible. (Implementation also lives in `TargetPassConfig.cpp`)
- `TargetPassConfig` is a polymorphic base (virtual inheritance) to build the target-dependent pipeline whereas `CodeGenPassBuilder` is the CRTP base/helper to implement the target-dependent pipeline. The motivation is flexibility for targets to customize the pipeline, inlining opportunity, and fits the overall NPM value semantics design.
- `TargetPassConfig` is a legacy immutable pass to declare hooks for targets to customize some target-independent codegen layer behavior. This is partially ported to TargetMachine::options. The rest, such as `createMachineScheduler/createPostMachineScheduler`, are left out for now. They should be implemented in LLVMTargetMachine in the future.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D83608

Author: Yuanfang Chen

llvm/include/llvm/CodeGen/CGPassBuilderOption.h

@@ -0,0 +1,110 @@
+//===- CGPassBuilderOption.h - Options for pass builder ---------*- 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 declares the options influencing building of codegen pipeline.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_CGPASSBUILDEROPTION_H
+#define LLVM_CODEGEN_CGPASSBUILDEROPTION_H
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Target/TargetOptions.h"
+#include <vector>
+
+namespace llvm {
+class TargetMachine;
+
+enum class RunOutliner { TargetDefault, AlwaysOutline, NeverOutline };
+enum class RegAllocType { Default, Basic, Fast, Greedy, PBQP };
+enum class CFLAAType { None, Steensgaard, Andersen, Both };
+
+// Not one-on-one but mostly corresponding to commandline options in
+// TargetPassConfig.cpp
+struct CGPassBuilderOption {
+  // Enable optimized register allocation compilation path
+  Optional<bool> OptimizeRegAlloc;
+
+  // Enable interprocedural register allocation to reduce load/store at
+  // procedure calls
+  Optional<bool> EnableIPRA;
+
+  // Enable debug logging of pass pipeline
+  bool DebugPM = false;
+
+  // Disable machine function verification
+  bool DisableVerify = false;
+
+  // Fold null checks into faulting memory operations
+  bool EnableImplicitNullChecksPass = false;
+
+  // Collect probability-driven block placement stats
+  bool EnableMachineBlockPlacementStatsPass = false;
+
+  // Run MachineScheduler post regalloc (independent of preRA sched)
+  bool EnablePostMachineSchedulerPass = false;
+
+  // Run live interval analysis earlier in the pipeline
+  bool EnableLiveIntervalsPass = false;
+
+  // Disable Loop Strength Reduction Pass
+  bool DisableLoopStrengthReducePass = false;
+
+  // Disable Codegen Prepare
+  bool DisableCodeGenPreparePass = false;
+
+  // Disable MergeICmps Pass
+  bool DisableMergeICmpsPass = false;
+
+  // Disable Partial Libcall Inlining Pass
+  bool DisablePartiallyInlineLibCallsPass = false;
+
+  // Disable ConstantHoisting Pass
+  bool DisableConstantHoistingPass = false;
+
+  // Print LLVM IR produced by the loop-reduce pass
+  bool PrintAfterLSR = false;
+
+  // Print LLVM IR input to isel pass
+  bool PrintISelInput = false;
+
+  // Dump garbage collector data
+  bool PrintGCInfo = false;
+
+  // Enable codegen in SCC order.
+  bool RequiresCodeGenSCCOrder = false;
+
+  // Enable the machine outliner
+  RunOutliner EnableMachineOutliner = RunOutliner::TargetDefault;
+
+  // Register allocator to use
+  RegAllocType RegAlloc = RegAllocType::Default;
+
+  // Experimental option to use CFL-AA in codegen
+  CFLAAType UseCFLAA = CFLAAType::None;
+
+  // Enable abort calls when "global" instruction selection fails to
+  // lower/select an instruction
+  Optional<GlobalISelAbortMode> EnableGlobalISelAbort;
+
+  // Verify generated machine code"
+  Optional<bool> VerifyMachineCode;
+
+  // Enable the "fast" instruction selector
+  Optional<bool> EnableFastISelOption;
+
+  // Enable the "global" instruction selector
+  Optional<bool> EnableGlobalISelOption;
+};
+
+CGPassBuilderOption getCGPassBuilderOption();
+
+} // namespace llvm
+
+#endif // LLVM_CODEGEN_CGPASSBUILDEROPTION_H