[mlir][spirv] Add a generic "convert-to-spirv" pass

This commit implements a MVP version of an MLIR lowering pipeline to SPIR-V.
The goal is to have a better test coverage of SPIR-V compilation upstream,
and enable writing simple kernels by hand. The dialects supported in this
version include arith, vector (only 1-D vectors with size 2,3,4,8 or 16),
scf, ub, index, func and math.

mlir/include/mlir/Conversion/ConvertToSPIRV/ConvertToSPIRVPass.h

@@ -0,0 +1,22 @@
+//===- ConvertToSPIRVPass.h - Conversion to SPIR-V pass ---*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_CONVERSION_CONVERTTOSPIRV_CONVERTTOSPIRVPASS_H
+#define MLIR_CONVERSION_CONVERTTOSPIRV_CONVERTTOSPIRVPASS_H
+
+#include <memory>
+
+namespace mlir {
+class Pass;
+
+#define GEN_PASS_DECL_CONVERTTOSPIRVPASS
+#include "mlir/Conversion/Passes.h.inc"
+
+} // namespace mlir
+
+#endif // MLIR_CONVERSION_CONVERTTOSPIRV_CONVERTTOSPIRVPASS_H

mlir/include/mlir/Conversion/Passes.h

@@ -30,6 +30,7 @@
 #include "mlir/Conversion/ControlFlowToSPIRV/ControlFlowToSPIRV.h"
 #include "mlir/Conversion/ControlFlowToSPIRV/ControlFlowToSPIRVPass.h"
 #include "mlir/Conversion/ConvertToLLVM/ToLLVMPass.h"
+#include "mlir/Conversion/ConvertToSPIRV/ConvertToSPIRVPass.h"
 #include "mlir/Conversion/FuncToEmitC/FuncToEmitCPass.h"
 #include "mlir/Conversion/FuncToLLVM/ConvertFuncToLLVMPass.h"
 #include "mlir/Conversion/FuncToSPIRV/FuncToSPIRVPass.h"

mlir/include/mlir/Conversion/Passes.td

@@ -31,6 +31,18 @@ def ConvertToLLVMPass : Pass<"convert-to-llvm"> {
   ];
 }
 
+//===----------------------------------------------------------------------===//
+// ToSPIRV
+//===----------------------------------------------------------------------===//
+
+def ConvertToSPIRVPass : Pass<"convert-to-spirv"> {
+  let summary = "Convert to SPIR-V";
+  let description = [{
+    This is a generic pass to convert to SPIR-V.
+  }];
+  let dependentDialects = ["spirv::SPIRVDialect"];
+}
+
 //===----------------------------------------------------------------------===//
 // AffineToStandard
 //===----------------------------------------------------------------------===//

mlir/lib/Conversion/CMakeLists.txt

@@ -19,6 +19,7 @@ add_subdirectory(ControlFlowToLLVM)
 add_subdirectory(ControlFlowToSCF)
 add_subdirectory(ControlFlowToSPIRV)
 add_subdirectory(ConvertToLLVM)
+add_subdirectory(ConvertToSPIRV)
 add_subdirectory(FuncToEmitC)
 add_subdirectory(FuncToLLVM)
 add_subdirectory(FuncToSPIRV)

mlir/lib/Conversion/ConvertToSPIRV/CMakeLists.txt

@@ -0,0 +1,22 @@
+set(LLVM_OPTIONAL_SOURCES
+  ConvertToSPIRVPass.cpp
+)
+
+add_mlir_conversion_library(MLIRConvertToSPIRVPass
+  ConvertToSPIRVPass.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${MLIR_MAIN_INCLUDE_DIR}/mlir/Conversion/ConvertToSPIRV
+
+  DEPENDS
+  MLIRConversionPassIncGen
+
+  LINK_LIBS PUBLIC
+  MLIRIR
+  MLIRPass
+  MLIRRewrite
+  MLIRSPIRVConversion
+  MLIRSPIRVDialect
+  MLIRSupport
+  MLIRTransformUtils
+  )

mlir/lib/Conversion/ConvertToSPIRV/ConvertToSPIRVPass.cpp

@@ -0,0 +1,72 @@
+//===- ConvertToSPIRVPass.cpp - MLIR SPIR-V Conversion --------------------===//
+//
+// 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 "mlir/Conversion/ConvertToSPIRV/ConvertToSPIRVPass.h"
+#include "mlir/Conversion/ArithToSPIRV/ArithToSPIRV.h"
+#include "mlir/Conversion/FuncToSPIRV/FuncToSPIRV.h"
+#include "mlir/Conversion/IndexToSPIRV/IndexToSPIRV.h"
+#include "mlir/Conversion/SCFToSPIRV/SCFToSPIRV.h"
+#include "mlir/Conversion/UBToSPIRV/UBToSPIRV.h"
+#include "mlir/Conversion/VectorToSPIRV/VectorToSPIRV.h"
+#include "mlir/Dialect/Arith/Transforms/Passes.h"
+#include "mlir/Dialect/SPIRV/IR/SPIRVAttributes.h"
+#include "mlir/Dialect/SPIRV/IR/SPIRVDialect.h"
+#include "mlir/Dialect/SPIRV/Transforms/SPIRVConversion.h"
+#include "mlir/Dialect/Vector/Transforms/VectorRewritePatterns.h"
+#include "mlir/IR/PatternMatch.h"
+#include "mlir/Pass/Pass.h"
+#include "mlir/Rewrite/FrozenRewritePatternSet.h"
+#include "mlir/Transforms/DialectConversion.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+#include <memory>
+
+#define DEBUG_TYPE "convert-to-spirv"
+
+namespace mlir {
+#define GEN_PASS_DEF_CONVERTTOSPIRVPASS
+#include "mlir/Conversion/Passes.h.inc"
+} // namespace mlir
+
+using namespace mlir;
+
+namespace {
+
+/// A pass to perform the SPIR-V conversion.
+struct ConvertToSPIRVPass final
+    : impl::ConvertToSPIRVPassBase<ConvertToSPIRVPass> {
+
+public:
+  void runOnOperation() final {
+    MLIRContext *context = &getContext();
+    Operation *op = getOperation();
+
+    spirv::TargetEnvAttr targetAttr = spirv::lookupTargetEnvOrDefault(op);
+    SPIRVTypeConverter typeConverter(targetAttr);
+
+    RewritePatternSet patterns(context);
+    ScfToSPIRVContext scfToSPIRVContext;
+
+    // Populate patterns.
+    arith::populateCeilFloorDivExpandOpsPatterns(patterns);
+    arith::populateArithToSPIRVPatterns(typeConverter, patterns);
+    populateBuiltinFuncToSPIRVPatterns(typeConverter, patterns);
+    populateFuncToSPIRVPatterns(typeConverter, patterns);
+    index::populateIndexToSPIRVPatterns(typeConverter, patterns);
+    populateVectorToSPIRVPatterns(typeConverter, patterns);
+    populateSCFToSPIRVPatterns(typeConverter, scfToSPIRVContext, patterns);
+    ub::populateUBToSPIRVConversionPatterns(typeConverter, patterns);
+
+    std::unique_ptr<ConversionTarget> target =
+        SPIRVConversionTarget::get(targetAttr);
+
+    if (failed(applyPartialConversion(op, *target, std::move(patterns))))
+      return signalPassFailure();
+  }
+};
+
+} // namespace