From 92a295eb399508b7d8dd577950cd33426ca5ae91 Mon Sep 17 00:00:00 2001
From: Kiran Chandramohan <kiran.chandramohan@arm.com>
Date: Wed, 4 Mar 2020 23:36:21 +0000
Subject: [PATCH] [MLIR, OpenMP] Translation of OpenMP barrier construct to
 LLVM IR

Summary:
This patch adds support for translation of the OpenMP barrier construct to LLVM
IR. The OpenMP IRBuilder is used for this translation. In this patch the code
for translation is added to the existing LLVM dialect translation to LLVM IR.

The patch includes code changes and a testcase.

Reviewers: jdoerfert, nicolasvasilache, ftynse, rriddle, mehdi_amini

Reviewed By: ftynse, rriddle, mehdi_amini

Differential Revision: https://reviews.llvm.org/D72962
---
 mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h |  6 ++++++
 mlir/lib/Dialect/LLVMIR/CMakeLists.txt              |  4 ++--
 mlir/lib/Target/LLVMIR/ModuleTranslation.cpp        | 21 ++++++++++++++++++++-
 mlir/test/Target/openmp-llvm.mlir                   | 10 ++++++++++
 4 files changed, 38 insertions(+), 3 deletions(-)
 create mode 100644 mlir/test/Target/openmp-llvm.mlir

diff --git a/mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h b/mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h
index 84ee37a..fd6dc88 100644
--- a/mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h
+++ b/mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h
@@ -19,6 +19,7 @@
 #include "mlir/IR/Module.h"
 #include "mlir/IR/Value.h"
 
+#include "llvm/Frontend/OpenMP/OMPIRBuilder.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IRBuilder.h"
@@ -103,6 +104,11 @@ private:
   /// A converter for translating debug information.
   std::unique_ptr<detail::DebugTranslation> debugTranslation;
 
+  /// Builder for LLVM IR generation of OpenMP constructs.
+  std::unique_ptr<llvm::OpenMPIRBuilder> ompBuilder;
+  /// Precomputed pointer to OpenMP dialect.
+  const Dialect *ompDialect;
+
   /// Mappings between llvm.mlir.global definitions and corresponding globals.
   DenseMap<Operation *, llvm::GlobalValue *> globalsMapping;
 
diff --git a/mlir/lib/Dialect/LLVMIR/CMakeLists.txt b/mlir/lib/Dialect/LLVMIR/CMakeLists.txt
index b0c4eb2..8eafbd8 100644
--- a/mlir/lib/Dialect/LLVMIR/CMakeLists.txt
+++ b/mlir/lib/Dialect/LLVMIR/CMakeLists.txt
@@ -4,8 +4,8 @@ add_mlir_dialect_library(MLIRLLVMIR
   ADDITIONAL_HEADER_DIRS
   ${MLIR_MAIN_INCLUDE_DIR}/mlir/Dialect/LLVMIR
   )
-add_dependencies(MLIRLLVMIR MLIRLLVMOpsIncGen MLIRLLVMConversionsIncGen LLVMAsmParser LLVMCore LLVMSupport)
-target_link_libraries(MLIRLLVMIR LLVMAsmParser LLVMCore LLVMSupport MLIRIR)
+add_dependencies(MLIRLLVMIR MLIRLLVMOpsIncGen MLIRLLVMConversionsIncGen MLIROpenMP LLVMFrontendOpenMP LLVMAsmParser LLVMCore LLVMSupport)
+target_link_libraries(MLIRLLVMIR LLVMAsmParser LLVMCore LLVMSupport LLVMFrontendOpenMP MLIROpenMP MLIRIR)
 
 add_mlir_dialect_library(MLIRNVVMIR
   IR/NVVMDialect.cpp
diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
index 84985fc..6efc90d 100644
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -15,12 +15,14 @@
 
 #include "DebugTranslation.h"
 #include "mlir/Dialect/LLVMIR/LLVMDialect.h"
+#include "mlir/Dialect/OpenMP/OpenMPDialect.h"
 #include "mlir/IR/Attributes.h"
 #include "mlir/IR/Module.h"
 #include "mlir/IR/StandardTypes.h"
 #include "mlir/Support/LLVM.h"
 
 #include "llvm/ADT/SetVector.h"
+#include "llvm/Frontend/OpenMP/OMPIRBuilder.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
@@ -271,7 +273,9 @@ ModuleTranslation::ModuleTranslation(Operation *module,
                                      std::unique_ptr<llvm::Module> llvmModule)
     : mlirModule(module), llvmModule(std::move(llvmModule)),
       debugTranslation(
-          std::make_unique<DebugTranslation>(module, *this->llvmModule)) {
+          std::make_unique<DebugTranslation>(module, *this->llvmModule)),
+      ompDialect(
+          module->getContext()->getRegisteredDialect<omp::OpenMPDialect>()) {
   assert(satisfiesLLVMModule(mlirModule) &&
          "mlirModule should honor LLVM's module semantics.");
 }
@@ -374,6 +378,21 @@ LogicalResult ModuleTranslation::convertOperation(Operation &opInst,
     return success();
   }
 
+  if (opInst.getDialect() == ompDialect) {
+    if (!ompBuilder) {
+      ompBuilder =
+          std::move(std::make_unique<llvm::OpenMPIRBuilder>(*llvmModule));
+      ompBuilder->initialize();
+    }
+
+    if (isa<omp::BarrierOp>(opInst)) {
+      ompBuilder->CreateBarrier(builder.saveIP(), llvm::omp::OMPD_barrier);
+      return success();
+    }
+    return opInst.emitError("unsupported OpenMP operation: ")
+           << opInst.getName();
+  }
+
   return opInst.emitError("unsupported or non-LLVM operation: ")
          << opInst.getName();
 }
diff --git a/mlir/test/Target/openmp-llvm.mlir b/mlir/test/Target/openmp-llvm.mlir
new file mode 100644
index 0000000..fd9c6bc
--- /dev/null
+++ b/mlir/test/Target/openmp-llvm.mlir
@@ -0,0 +1,10 @@
+// RUN: mlir-translate -mlir-to-llvmir %s | FileCheck %s
+
+// CHECK-LABEL: define void @empty()
+// CHECK: [[OMP_THREAD:%.*]] = call i32 @__kmpc_global_thread_num(%struct.ident_t* @{{[0-9]+}})
+// CHECK-NEXT:  call void @__kmpc_barrier(%struct.ident_t* @{{[0-9]+}}, i32 [[OMP_THREAD]])
+// CHECK-NEXT:    ret void
+llvm.func @empty() {
+  omp.barrier
+  llvm.return
+}
-- 
2.7.4