[llvm] [SandboxVectorizer] Use sbvec-passes flag to create a pipeline of Region passes after BottomUpVec. (PR #111223)

[via llvm-commits]

================
@@ -10,10 +10,69 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/SandboxIR/Function.h"
 #include "llvm/SandboxIR/Instruction.h"
-
-using namespace llvm::sandboxir;
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Transforms/Vectorize/SandboxVectorizer/Passes/NullPass.h"
 
 namespace llvm::sandboxir {
+
+static cl::opt<bool>
+    PrintPassPipeline("sbvec-print-pass-pipeline", cl::init(false), cl::Hidden,
+                      cl::desc("Prints the pass pipeline and returns."));
+
+/// A magic string for the default pass pipeline.
+static const char *DefaultPipelineMagicStr = "*";
+
+static cl::opt<std::string> UserDefinedPassPipeline(
+    "sbvec-passes", cl::init(DefaultPipelineMagicStr), cl::Hidden,
+    cl::desc("Comma-separated list of vectorizer passes. If not set "
+             "we run the predefined pipeline."));
+
+static std::unique_ptr<RegionPass> createRegionPass(StringRef Name) {
+#define REGION_PASS(NAME, CREATE_PASS)                                         \
+  if (Name == NAME)                                                            \
+    return std::make_unique<decltype(CREATE_PASS)>(CREATE_PASS);
+#include "PassRegistry.def"
+  return nullptr;
+}
+
+/// Adds to `RPM` a sequence of region passes described by `Pipeline`.
+static void parseAndCreatePassPipeline(RegionPassManager &RPM,
----------------
vporpo wrote:

I meant making `parseAndCreatePassPipeline` a member function of `PassManager` such that we call:
```
RPM.parseAndCreatePassPipeline(UserDefinedPassPipeline);
```
instead of:
```
parseAndCreatePassPipeline(RPM, UserDefinedPassPipeline);
```

https://github.com/llvm/llvm-project/pull/111223