[flang-commits] [flang] 4741835 - [flang] Add the helper class for building fir.do_loop operations. A fir.do_loop models the semantics of a Fortran DO loop construct. One can use this operation to explicitly capture a DO loop for passing into the high-level optimizer.

[Eric Schweitz via flang-commits]

Author: Eric Schweitz
Date: 2020-06-12T17:28:00-07:00
New Revision: 4741835e031b559f2effcad70f59e35c32c1eece

URL: https://github.com/llvm/llvm-project/commit/4741835e031b559f2effcad70f59e35c32c1eece
DIFF: https://github.com/llvm/llvm-project/commit/4741835e031b559f2effcad70f59e35c32c1eece.diff

LOG: [flang] Add the helper class for building fir.do_loop operations. A fir.do_loop models the semantics of a Fortran DO loop construct. One can use this operation to explicitly capture a DO loop for passing into the high-level optimizer.

Differential revision: https://reviews.llvm.org/D81692

Added: 
    flang/include/flang/Lower/DoLoopHelper.h
    flang/lib/Lower/DoLoopHelper.cpp

Modified: 
    flang/lib/Lower/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/flang/include/flang/Lower/DoLoopHelper.h b/flang/include/flang/Lower/DoLoopHelper.h
new file mode 100644
index 000000000000..12901e9eb7a6
--- /dev/null
+++ b/flang/include/flang/Lower/DoLoopHelper.h
@@ -0,0 +1,45 @@
+//===-- Lower/DoLoopHelper.h -- gen fir.do_loop ops -------------*- 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 FORTRAN_LOWER_DOLOOPHELPER_H
+#define FORTRAN_LOWER_DOLOOPHELPER_H
+
+#include "flang/Lower/FIRBuilder.h"
+
+namespace Fortran::lower {
+
+/// Helper to build fir.do_loop Ops.
+class DoLoopHelper {
+public:
+  explicit DoLoopHelper(FirOpBuilder &builder, mlir::Location loc)
+      : builder(builder), loc(loc) {}
+  DoLoopHelper(const DoLoopHelper &) = delete;
+
+  /// Type of a callback to generate the loop body.
+  using BodyGenerator = std::function<void(FirOpBuilder &, mlir::Value)>;
+
+  /// Build loop [\p lb, \p ub] with step \p step.
+  /// If \p step is an empty value, 1 is used for the step.
+  void createLoop(mlir::Value lb, mlir::Value ub, mlir::Value step,
+                  const BodyGenerator &bodyGenerator);
+
+  /// Build loop [\p lb,  \p ub] with step 1.
+  void createLoop(mlir::Value lb, mlir::Value ub,
+                  const BodyGenerator &bodyGenerator);
+
+  /// Build loop [0, \p count) with step 1.
+  void createLoop(mlir::Value count, const BodyGenerator &bodyGenerator);
+
+private:
+  FirOpBuilder &builder;
+  mlir::Location loc;
+};
+
+} // namespace Fortran::lower
+
+#endif // FORTRAN_LOWER_DOLOOPHELPER_H

diff  --git a/flang/lib/Lower/CMakeLists.txt b/flang/lib/Lower/CMakeLists.txt
index 321fb65fbe4f..8bdac3ca3eac 100644
--- a/flang/lib/Lower/CMakeLists.txt
+++ b/flang/lib/Lower/CMakeLists.txt
@@ -1,11 +1,18 @@
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-error -Wno-unused-parameter")
 
 add_flang_library(FortranLower
-  ConvertType.cpp
   ComplexExpr.cpp
+  ConvertType.cpp
+  DoLoopHelper.cpp
   OpenMP.cpp
   PFTBuilder.cpp
 
+  DEPENDS
+  FIROpsIncGen
+  MLIROpAsmInterfaceIncGen
+  MLIRControlFlowInterfaces
+  MLIRLinalgStructuredOpsInterfaceIncGen
+
   LINK_COMPONENTS
   Support
 )

diff  --git a/flang/lib/Lower/DoLoopHelper.cpp b/flang/lib/Lower/DoLoopHelper.cpp
new file mode 100644
index 000000000000..35ef7434daaa
--- /dev/null
+++ b/flang/lib/Lower/DoLoopHelper.cpp
@@ -0,0 +1,44 @@
+//===-- DoLoopHelper.cpp --------------------------------------------------===//
+//
+// 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 "flang/Lower/DoLoopHelper.h"
+
+//===----------------------------------------------------------------------===//
+// DoLoopHelper implementation
+//===----------------------------------------------------------------------===//
+
+void Fortran::lower::DoLoopHelper::createLoop(
+    mlir::Value lb, mlir::Value ub, mlir::Value step,
+    const BodyGenerator &bodyGenerator) {
+  auto lbi = builder.convertToIndexType(loc, lb);
+  auto ubi = builder.convertToIndexType(loc, ub);
+  assert(step && "step must be an actual Value");
+  auto inc = builder.convertToIndexType(loc, step);
+  auto loop = builder.create<fir::LoopOp>(loc, lbi, ubi, inc);
+  auto insertPt = builder.saveInsertionPoint();
+  builder.setInsertionPointToStart(loop.getBody());
+  auto index = loop.getInductionVar();
+  bodyGenerator(builder, index);
+  builder.restoreInsertionPoint(insertPt);
+}
+
+void Fortran::lower::DoLoopHelper::createLoop(
+    mlir::Value lb, mlir::Value ub, const BodyGenerator &bodyGenerator) {
+  createLoop(lb, ub,
+             builder.createIntegerConstant(loc, builder.getIndexType(), 1),
+             bodyGenerator);
+}
+
+void Fortran::lower::DoLoopHelper::createLoop(
+    mlir::Value count, const BodyGenerator &bodyGenerator) {
+  auto indexType = builder.getIndexType();
+  auto zero = builder.createIntegerConstant(loc, indexType, 0);
+  auto one = builder.createIntegerConstant(loc, count.getType(), 1);
+  auto up = builder.create<mlir::SubIOp>(loc, count, one);
+  createLoop(zero, up, one, bodyGenerator);
+}