[MLIR] Graph pass to lower standardDialect to llvm module (#3810)

* Re-organize files. Create MLIR backend classes

* WIP

* Refactored. Code compiles

* Moved context to Runtime class to outlive compilation and execution

* style-apply

* Base Runtime class. Few other modifications

* Minor fixes

* Fixed Runtime::run() to take type-erased pointer

* renamed core compiler

* rename backend compiler

* rename runtime compiler

* PR feedback

* Fix build fails

* - refactor LowerNGDialect
- addgraph pass to lower standardDialect to llvm module

* Addressed PR Comments

* i) Style fix ii) restore deleted file

src/contrib/mlir/backend/cpu/cpu_backend.cpp

@@ -188,23 +188,27 @@ void MLIRCPUBackend::lowerNgDialect()
 
     NGRAPH_CHECK(m_module, "MLIR module is not ready.");
 
-    // Lower Standard dialect to LLVM dialect.
-    mlir::LLVMTypeConverter llvmConverter(&m_context);
-    mlir::OwningRewritePatternList patterns;
-    mlir::populateLoopToStdConversionPatterns(patterns, &m_context);
-    mlir::populateStdToLLVMConversionPatterns(llvmConverter, patterns);
-
-    mlir::ConversionTarget target(m_context);
-    target.addLegalDialect<mlir::LLVM::LLVMDialect>();
-    target.addLegalOp<mlir::ModuleOp, mlir::ModuleTerminatorOp>();
-    target.addDynamicallyLegalOp<mlir::FuncOp>(
-        [&](mlir::FuncOp op) { return llvmConverter.isSignatureLegal(op.getType()); });
-
-    auto result =
-        mlir::applyFullConversion(m_module.get(), target, std::move(patterns), &llvmConverter);
-    NGRAPH_CHECK(succeeded(result), "Standard to LLVM dialect conversion failed");
-
-    dumpMlirModule("LLVM-IR Dialect Conversion", m_module.get());
+    lowerStandardDialect();
+}
+
+// Lower Standard dialect to LLVM dialect
+void MLIRCPUBackend::lowerStandardDialect()
+{
+    mlir::PassManager pm(&m_context);
+    pm.addPass(mlir::createLowerToLLVMPass());
+
+    // Apply any generic pass manager command line options.
+    mlir::applyPassManagerCLOptions(pm);
+
+    if (failed(pm.run(m_module.get())))
+    {
+        NGRAPH_CHECK(false, "MLIR pass manager failed");
+    }
+
+    if (failed(m_module->verify()))
+    {
+        NGRAPH_CHECK(false, "Incorrect module after dialect lowering");
+    }
 }
 
 // Receives affine dialect as input and applies affine and standard dialect based optimizations.

src/contrib/mlir/backend/cpu/cpu_backend.hpp

@@ -60,8 +60,13 @@ namespace ngraph
             private:
                 // Apply CPU specific optimizations at nGraph dialect level
                 void optimizeNgDialect();
-                // Lowers nGraph dialect all the way to LLVM module.
+
+                // Lowers nGraph dialect all the way to Affine dialect.
                 void lowerNgDialect();
+
+                // Lowers standard dialect all the way to LLVM dialect.
+                void lowerStandardDialect();
+
                 // Apply affine dialect optimizations
                 void optimizeAffineDialect();