[mlir][ptr] Add conversion to LLVM for all existing ptr ops (llvm#156053)

This patch adds conversion to LLVM for all existing pointer ops. This is
a stop gap measure to allow users to use the `ptr` dialect now. In the
future some of these conversions will be removed, and added as
translations, for example `ptradd`.

Example:
```mlir
func.func @test_memref_ptradd_indexing(%arg0: memref<10x?x30xf32, #ptr.generic_space>, %arg1: index) -> !ptr.ptr<#ptr.generic_space> {
  %0 = ptr.to_ptr %arg0 : memref<10x?x30xf32, #ptr.generic_space> -> <#ptr.generic_space>
  %1 = ptr.type_offset f32 : index
  %2 = arith.muli %1, %arg1 : index
  %3 = ptr.ptr_add %0, %2 : <#ptr.generic_space>, index
  return %3 : !ptr.ptr<#ptr.generic_space>
}
// mlir-opt --convert-to-llvm --canonicalize --cse
llvm.func @test_memref_ptradd_indexing(%arg0: !llvm.ptr, %arg1: !llvm.ptr, %arg2: i64, %arg3: i64, %arg4: i64, %arg5: i64, %arg6: i64, %arg7: i64, %arg8: i64, %arg9: i64) -> !llvm.ptr {
  %0 = llvm.mlir.zero : !llvm.ptr
  %1 = llvm.getelementptr %0[1] : (!llvm.ptr) -> !llvm.ptr, f32
  %2 = llvm.ptrtoint %1 : !llvm.ptr to i64
  %3 = llvm.mul %2, %arg9 : i64
  %4 = llvm.getelementptr %arg1[%3] : (!llvm.ptr, i64) -> !llvm.ptr, i8
  llvm.return %4 : !llvm.ptr
}
```

Author: fabianmcg

mlir/include/mlir/Conversion/PtrToLLVM/PtrToLLVM.h

@@ -0,0 +1,27 @@
+//===- PtrToLLVM.h - Ptr to LLVM dialect conversion -------------*- 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_PTRTOLLVM_PTRTOLLVM_H
+#define MLIR_CONVERSION_PTRTOLLVM_PTRTOLLVM_H
+
+#include <memory>
+
+namespace mlir {
+class DialectRegistry;
+class LLVMTypeConverter;
+class RewritePatternSet;
+namespace ptr {
+/// Populate the convert to LLVM patterns for the `ptr` dialect.
+void populatePtrToLLVMConversionPatterns(LLVMTypeConverter &converter,
+                                         RewritePatternSet &patterns);
+/// Register the convert to LLVM interface for the `ptr` dialect.
+void registerConvertPtrToLLVMInterface(DialectRegistry &registry);
+} // namespace ptr
+} // namespace mlir
+
+#endif // MLIR_CONVERSION_PTRTOLLVM_PTRTOLLVM_H

mlir/lib/Conversion/CMakeLists.txt

@@ -50,6 +50,7 @@ add_subdirectory(NVVMToLLVM)
 add_subdirectory(OpenACCToSCF)
 add_subdirectory(OpenMPToLLVM)
 add_subdirectory(PDLToPDLInterp)
+add_subdirectory(PtrToLLVM)
 add_subdirectory(ReconcileUnrealizedCasts)
 add_subdirectory(SCFToControlFlow)
 add_subdirectory(SCFToEmitC)

mlir/lib/Conversion/PtrToLLVM/CMakeLists.txt

@@ -0,0 +1,17 @@
+add_mlir_conversion_library(MLIRPtrToLLVM
+  PtrToLLVM.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${MLIR_MAIN_INCLUDE_DIR}/mlir/Conversion/PtrToLLVM
+
+  DEPENDS
+  MLIRConversionPassIncGen
+
+  LINK_COMPONENTS
+  Core
+
+  LINK_LIBS PUBLIC
+  MLIRPtrDialect
+  MLIRLLVMCommonConversion
+  MLIRLLVMDialect
+  )