[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, aeubanks

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

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPassBuilder.cpp b/llvm/lib/CodeGen/CodeGenPassBuilder.cpp
new file mode 100644
index 0000000..7f37f20
--- /dev/null
+++ b/llvm/lib/CodeGen/CodeGenPassBuilder.cpp
@@ -0,0 +1,25 @@
+//===--- CodeGenPassBuilder.cpp --------------------------------------- ---===//
+//
+// 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 defines interfaces to access the target independent code
+// generation passes provided by the LLVM backend.
+//
+//===---------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/CodeGenPassBuilder.h"
+
+using namespace llvm;
+
+namespace llvm {
+#define DUMMY_MACHINE_MODULE_PASS(NAME, PASS_NAME, CONSTRUCTOR)                \
+  AnalysisKey PASS_NAME::Key;
+#include "llvm/CodeGen/MachinePassRegistry.def"
+#define DUMMY_MACHINE_FUNCTION_PASS(NAME, PASS_NAME, CONSTRUCTOR)              \
+  AnalysisKey PASS_NAME::Key;
+#include "llvm/CodeGen/MachinePassRegistry.def"
+} // namespace llvm