[flang] Introduce FortranVariableOpInterface for ops creating variable

[jeanPerier]

Summary

HLFIR will rely on certain operations to create SSA memory values
that correspond to a Fortran variable. They will hold bounds and type
parameters information as well as metadata (like Fortran attributes).

This patch adds an interface that for such operations so that Fortran
variable can be stored, manipulated, and queried regardless of what
created them. This is so far intended for fir.declare, hlfir.designate
and hlfir.associate operations.
It is added to FIR and not HLFIR because fir.declare needs it and it
does not itself needs any HLFIR concepts.

Unit tests for the interface methods will be added alongside
fir.declare in the next patch.

[clementval]

LGTM. There is a small type in the revision title.

[PeteSteinfeld]

Looking good! Aside from a few nits, all builds and tests correctly and looks good.

flang/include/flang/Optimizer/Dialect/FortranVariableInterface.td

10

Should read "This file defines"

22

Should this be "Interface for operations that create"?

[jeanPerier]

Fix typos in descriptions.

[jeanPerier]

Thanks for spotting the typos Pete and Valentin.

[vzakhari]

flang/include/flang/Optimizer/Dialect/FortranVariableInterface.td

112

Is it worth asserting that getExplicitTypeParams returns an empty range or a range with exactly one element, when isCharacter is true?

[jeanPerier]

flang/include/flang/Optimizer/Dialect/FortranVariableInterface.td

112

Yes, this will actually be done in the FortranVariableOpInterface verifier that I am adding in https://reviews.llvm.org/D136181 (see fir::FortranVariableOpInterface::verifyImpl) (it won't be an assertion though, but an MLIR verifier error with line location).

[DavidSpickett]

FYI this is failing on the out of tree flang bot: https://lab.llvm.org/buildbot/#/builders/175/builds/19348

For reasons I can't explain, this commit isn't listed in any of the builds but I confirmed locally (I think the buildbot config is a bit strange).

Anyway, it appears that when we build flang, this new .h.inc file is not created. There are others that are so I will see if we can just follow their lead to fix this.

In tree builds are fine.

[DavidSpickett]

Potential fix in https://reviews.llvm.org/D136250.

flang/include/flang/Optimizer/Dialect/CMakeLists.txt

 # This replicates part of the add_mlir_dialect cmake function from MLIR that
 # cannot be used her because it expects to be run inside MLIR directory which
 # is not the case for FIR.
 set(LLVM_TARGET_DEFINITIONS FIRAttr.td)
 mlir_tablegen(FIREnumAttr.h.inc -gen-enum-decls)
 mlir_tablegen(FIREnumAttr.cpp.inc -gen-enum-defs)
 mlir_tablegen(FIRAttr.h.inc --gen-attrdef-decls)
 mlir_tablegen(FIRAttr.cpp.inc -gen-attrdef-defs)
 
 set(LLVM_TARGET_DEFINITIONS FIROps.td)
 mlir_tablegen(FIROps.h.inc -gen-op-decls)
 mlir_tablegen(FIROps.cpp.inc -gen-op-defs)
 mlir_tablegen(FIROpsTypes.h.inc --gen-typedef-decls)
 mlir_tablegen(FIROpsTypes.cpp.inc --gen-typedef-defs)
+add_mlir_interface(FortranVariableInterface)
 add_public_tablegen_target(FIROpsIncGen)
 
 set(LLVM_TARGET_DEFINITIONS CanonicalizationPatterns.td)
 mlir_tablegen(CanonicalizationPatterns.inc -gen-rewriters)
 add_public_tablegen_target(CanonicalizationPatternsIncGen)
 
 add_custom_target(flang-doc)
 set(dialect_doc_filename "FIRLangRef")

flang/include/flang/Optimizer/Dialect/FortranVariableInterface.h

+//===- FortranVariableInterface.h -------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains a set of interfaces for operations defining Fortran
+// variables.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_OPTIMIZER_DIALECT_FORTRANVARIABLEINTERFACE_H
+#define FORTRAN_OPTIMIZER_DIALECT_FORTRANVARIABLEINTERFACE_H
+
+#include "flang/Optimizer/Dialect/FIRAttr.h"
+#include "flang/Optimizer/Dialect/FIRType.h"
+#include "mlir/IR/BuiltinTypes.h"
+#include "mlir/IR/OpDefinition.h"
+
+namespace fir {
+#include "flang/Optimizer/Dialect/FortranVariableInterface.h.inc"
+} // namespace fir
+
+#endif // FORTRAN_OPTIMIZER_DIALECT_FORTRANVARIABLEINTERFACE_H

flang/include/flang/Optimizer/Dialect/FortranVariableInterface.td

+//===- FortranVariableInterface.td -------------------------*- tablegen -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines an interface for operations defining Fortran variables.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRANVARIABLEINTERFACE
+#define FORTRANVARIABLEINTERFACE
+
+include "mlir/IR/OpBase.td"
+
+
+def FortranVariableOpInterface : OpInterface<"FortranVariableOpInterface"> {
+  let description = [{
+    Interface for operations that create Fortran like variables in order to
+    query about all their Fortran properties.
+  }];
+
+  let methods = [
+    InterfaceMethod<
+      /*desc=*/"Get the address produced by the definition",
+      /*retTy=*/"mlir::Value",
+      /*methodName=*/"getBase",
+      /*args=*/(ins),
+      /*methodBody=*/[{}],
+      /*defaultImplementation=*/[{
+        ConcreteOp op = mlir::cast<ConcreteOp>(this->getOperation());
+        return op.getResult();
+      }]
+    >,
+    InterfaceMethod<
+      /*desc=*/"Get Fortran attributes",
+      /*retTy=*/"llvm::Optional<fir::FortranVariableFlagsEnum>",
+      /*methodName=*/"getFortranAttrs",
+      /*args=*/(ins),
+      /*methodBody=*/[{}],
+      /*defaultImplementation=*/[{
+        ConcreteOp op = mlir::cast<ConcreteOp>(this->getOperation());
+        return op.getFortran_attrs();
+      }]
+    >,
+    InterfaceMethod<
+      /*desc=*/"Get the shape of the variable",
+      /*retTy=*/"llvm::Optional<mlir::Value>",
+      /*methodName=*/"getShape",
+      /*args=*/(ins),
+      /*methodBody=*/[{}],
+      /*defaultImplementation=*/[{
+        ConcreteOp op = mlir::cast<ConcreteOp>(this->getOperation());
+        return op.getShape();
+      }]
+    >,
+    InterfaceMethod<
+      /*desc=*/"Get explicit type parameters of the variable",
+      /*retTy=*/"mlir::OperandRange",
+      /*methodName=*/"getExplicitTypeParams",
+      /*args=*/(ins),
+      /*methodBody=*/[{}],
+      /*defaultImplementation=*/[{
+        ConcreteOp op = mlir::cast<ConcreteOp>(this->getOperation());
+        return op.getTypeparams();
+      }]
+    >,
+  ];
+
+  let extraClassDeclaration = [{
+
+    /// Get the sequence type or scalar value type corresponding to this
+    /// variable.
+    mlir::Type getElementOrSequenceType() {
+      return fir::unwrapPassByRefType(getBase().getType());
+    }
+
+    /// Get the scalar value type corresponding to this variable.
+    mlir::Type getElementType() {
+      return fir::unwrapSequenceType(getElementOrSequenceType());
+    }
+
+    /// Is the variable an array ?
+    bool isArray() {
+      return getElementOrSequenceType().isa<fir::SequenceType>();
+    }
+
+    /// Is this variable a Fortran pointer ?
+    bool isPointer() {
+      auto attrs = getFortranAttrs();
+      return attrs && bitEnumContainsAny(*attrs,
+                        fir::FortranVariableFlagsEnum::pointer);
+    }
+
+    /// Is this variable a Fortran allocatable ?
+    bool isAllocatable() {
+      auto attrs = getFortranAttrs();
+      return attrs && bitEnumContainsAny(*attrs,
+                        fir::FortranVariableFlagsEnum::allocatable);
+    }
+
+    /// Is this a Fortran character variable ?
+    bool isCharacter() {
+      return getElementType().isa<fir::CharacterType>();
+    }
+
+    /// Is this a Fortran character variable with an explicit length ?
+    bool hasExplicitCharLen() {
+      return isCharacter() && !getExplicitTypeParams().empty();
+    }
+
+    /// Return the length of explicit length character variable.
+    mlir::Value getExplicitCharLen() {
+      assert(hasExplicitCharLen() && "must be an explicit length character");
+      return getExplicitTypeParams()[0];
+    }
+
+  }];
+
+}
+
+#endif  // FORTRANVARIABLEINTERFACE

flang/lib/Optimizer/Dialect/CMakeLists.txt

 add_flang_library(FIRDialect
   FIRAttr.cpp
   FIRDialect.cpp
   FIROps.cpp
   FIRType.cpp
+  FortranVariableInterface.cpp
   Inliner.cpp
 
   DEPENDS
   CanonicalizationPatternsIncGen
   FIRSupport
   FIROpsIncGen
 
   LINK_LIBS

flang/lib/Optimizer/Dialect/FortranVariableInterface.cpp

+//===-- FortranVariableInterface.cpp.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
+//
+//===----------------------------------------------------------------------===//
+//
+// Coding style: https://mlir.llvm.org/getting_started/DeveloperGuide/
+//
+//===----------------------------------------------------------------------===//
+
+#include "flang/Optimizer/Dialect/FortranVariableInterface.h"
+
+namespace fir {
+#include "flang/Optimizer/Dialect/FortranVariableInterface.cpp.inc"
+}