[Mlir-commits] [mlir] [MLIR][MPI] Add LLVM lowering patterns for some MPI operations (PR #95524)

[Markus Böck]

================
@@ -0,0 +1,230 @@
+//===- MPIToLLVM.cpp - MPI to LLVM dialect 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/MPIToLLVM/MPIToLLVM.h"
+
+#include "mlir/Conversion/LLVMCommon/Pattern.h"
+#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
+#include "mlir/Dialect/MPI/IR/MPI.h"
+#include "mlir/Pass/Pass.h"
+
+#include <mlir/Conversion/ConvertToLLVM/ToLLVMInterface.h>
+
+using namespace mlir;
+
+namespace {
+
+struct InitOpLowering : ConvertOpToLLVMPattern<mpi::InitOp> {
+  using ConvertOpToLLVMPattern::ConvertOpToLLVMPattern;
+
+  LogicalResult
+  matchAndRewrite(mpi::InitOp op, OpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override;
+};
+
+struct CommRankOpLowering : ConvertOpToLLVMPattern<mpi::CommRankOp> {
+  using ConvertOpToLLVMPattern::ConvertOpToLLVMPattern;
+
+  LogicalResult
+  matchAndRewrite(mpi::CommRankOp op, OpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override;
+};
+
+struct FinalizeOpLowering : ConvertOpToLLVMPattern<mpi::FinalizeOp> {
+  using ConvertOpToLLVMPattern::ConvertOpToLLVMPattern;
+
+  LogicalResult
+  matchAndRewrite(mpi::FinalizeOp op, OpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override;
+};
+
+// TODO: this was copied from GPUOpsLowering.cpp:288
+// is this okay, or should this be moved to some common file?
+LLVM::LLVMFuncOp getOrDefineFunction(ModuleOp &moduleOp, const Location loc,
+                                     ConversionPatternRewriter &rewriter,
+                                     StringRef name,
+                                     LLVM::LLVMFunctionType type) {
+  LLVM::LLVMFuncOp ret;
+  if (!(ret = moduleOp.lookupSymbol<LLVM::LLVMFuncOp>(name))) {
+    ConversionPatternRewriter::InsertionGuard guard(rewriter);
+    rewriter.setInsertionPointToStart(moduleOp.getBody());
+    ret = rewriter.create<LLVM::LLVMFuncOp>(loc, name, type,
+                                            LLVM::Linkage::External);
+  }
+  return ret;
+}
+
+// TODO: this is pretty close to getOrDefineFunction, can probably be factored
+LLVM::GlobalOp getOrDefineExternalStruct(ModuleOp &moduleOp, const Location loc,
+                                         ConversionPatternRewriter &rewriter,
+                                         StringRef name,
+                                         LLVM::LLVMStructType type) {
+  LLVM::GlobalOp ret;
+  if (!(ret = moduleOp.lookupSymbol<LLVM::GlobalOp>(name))) {
+    ConversionPatternRewriter::InsertionGuard guard(rewriter);
+    rewriter.setInsertionPointToStart(moduleOp.getBody());
+    ret = rewriter.create<LLVM::GlobalOp>(
+        loc, type, /*isConstant=*/false, LLVM::Linkage::External, name,
+        /*value=*/Attribute(), /*alignment=*/0, 0);
+  }
+  return ret;
+}
+
+} // namespace
+
+//===----------------------------------------------------------------------===//
+// InitOpLowering
+//===----------------------------------------------------------------------===//
+
+LogicalResult
+InitOpLowering::matchAndRewrite(mpi::InitOp op, OpAdaptor adaptor,
+                                ConversionPatternRewriter &rewriter) const {
+  // get loc
+  auto loc = op.getLoc();
+
+  // ptrType `!llvm.ptr`
+  Type ptrType = LLVM::LLVMPointerType::get(rewriter.getContext());
+
+  // instantiate nullptr `%nullptr = llvm.mlir.zero : !llvm.ptr`
+  auto nullPtrOp = rewriter.create<LLVM::ZeroOp>(loc, ptrType);
+  Value llvmnull = nullPtrOp.getRes();
+
+  // grab a reference to the global module op:
+  auto moduleOp = op->getParentOfType<ModuleOp>();
+
+  // LLVM Function type representing `i32 MPI_Init(ptr, ptr)`
+  auto initFuncType =
+      LLVM::LLVMFunctionType::get(rewriter.getI32Type(), {ptrType, ptrType});
+  // get or create function declaration:
+  LLVM::LLVMFuncOp initDecl =
+      getOrDefineFunction(moduleOp, loc, rewriter, "MPI_Init", initFuncType);
+
+  // replace init with function call
+  rewriter.replaceOpWithNewOp<LLVM::CallOp>(op, initDecl,
+                                            ValueRange{llvmnull, llvmnull});
+
+  return success();
+}
+
+//===----------------------------------------------------------------------===//
+// FinalizeOpLowering
+//===----------------------------------------------------------------------===//
+
+LogicalResult
+FinalizeOpLowering::matchAndRewrite(mpi::FinalizeOp op, OpAdaptor adaptor,
+                                    ConversionPatternRewriter &rewriter) const {
+  // get loc
+  auto loc = op.getLoc();
+
+  // grab a reference to the global module op:
+  auto moduleOp = op->getParentOfType<ModuleOp>();
+
+  // LLVM Function type representing `i32 MPI_Finalize()`
+  auto initFuncType = LLVM::LLVMFunctionType::get(rewriter.getI32Type(), {});
+  // get or create function declaration:
+  LLVM::LLVMFuncOp initDecl = getOrDefineFunction(moduleOp, loc, rewriter,
+                                                  "MPI_Finalize", initFuncType);
+
+  // replace init with function call
+  rewriter.replaceOpWithNewOp<LLVM::CallOp>(op, initDecl, ValueRange{});
+
+  return success();
+}
+
+//===----------------------------------------------------------------------===//
+// CommRankLowering
+//===----------------------------------------------------------------------===//
+
+LogicalResult
+CommRankOpLowering::matchAndRewrite(mpi::CommRankOp op, OpAdaptor adaptor,
+                                    ConversionPatternRewriter &rewriter) const {
+  // get some helper vars
+  auto loc = op.getLoc();
+  auto context = rewriter.getContext();
+  auto i32 = rewriter.getI32Type();
+
+  // ptrType `!llvm.ptr`
+  Type ptrType = LLVM::LLVMPointerType::get(context);
+
+  // get external opaque struct pointer type
+  auto commStructT = LLVM::LLVMStructType::getOpaque("MPI_ABI_Comm", context);
+
+  // grab a reference to the global module op:
+  auto moduleOp = op->getParentOfType<ModuleOp>();
+
+  // make sure global op definition exists
+  getOrDefineExternalStruct(moduleOp, loc, rewriter, "MPI_COMM_WORLD",
+                            commStructT);
+
+  // get address of @MPI_COMM_WORLD
+  auto one = rewriter.create<LLVM::ConstantOp>(loc, i32, 1);
+  auto rankptr = rewriter.create<LLVM::AllocaOp>(loc, ptrType, i32, one);
+  auto commWorld = rewriter.create<LLVM::AddressOfOp>(
+      loc, ptrType, SymbolRefAttr::get(context, "MPI_COMM_WORLD"));
+
+  // LLVM Function type representing `i32 MPI_Comm_rank(ptr, ptr)`
+  auto rankFuncType = LLVM::LLVMFunctionType::get(i32, {ptrType, ptrType});
+  // get or create function declaration:
+  LLVM::LLVMFuncOp initDecl = getOrDefineFunction(
+      moduleOp, loc, rewriter, "MPI_Comm_rank", rankFuncType);
+
+  // replace init with function call
+  auto callOp = rewriter.create<LLVM::CallOp>(
+      loc, initDecl, ValueRange{commWorld.getRes(), rankptr.getRes()});
+
+  // load the rank into a register
+  auto loadedRank =
+      rewriter.create<LLVM::LoadOp>(loc, i32, rankptr.getResult());
+
+  // if retval is checked, replace uses of retval with the results from the call
+  // op
+  SmallVector<Value> replacements;
+  if (op.getRetval()) {
+    replacements.push_back(callOp.getResult());
+  }
----------------
zero9178 wrote:

```suggestion
  if (op.getRetval()) 
    replacements.push_back(callOp.getResult());
  
```

https://github.com/llvm/llvm-project/pull/95524