[flang] Add runtime interface for NUM_IMAGES

[craig.rasmussen]

Summary

NUM_IMAGES takes optional arguments TEAM and TEAM_NUMBER.

This patch provides an interface for only the optional TEAM_NUMBER dummy argument. It is likely that a different function will be required to support TEAM arguments.

[craig.rasmussen]

flang/runtime/coarray.h

21 ↗

(On Diff #371727)

I think the default (team_number = 0) should work here because when forming a new team (11.6.9 FORM TEAM statement) the team_number has to be greater than 0. In 9.6 paragraph 3 the team number has to be from a FORM TEAM statement or be the initial team. In 16.9.189 TEAM_NUMBER paragraph 5 it states that the initial team shall have the value -1.

So team_number==0 isn't a valid team number and can represent NUM_IMAGES called with no actual arguments.

[PeteSteinfeld]

flang/runtime/coarray.h

1 ↗

(On Diff #371727)

Note that patch https://reviews.llvm.org/D109107 rearranged the location of the runtime header files. So the correct location for coarray.h is now .../flang/include/flang/Runtime.

15 ↗

(On Diff #371727)

With the new file organization, the #include statement for entry-names.h is

#include "flang/Runtime/entry-names.h"

21 ↗

(On Diff #371727)

The interface looks OK to me for two of the three forms of NUM_IMAGES. We'll probably want a second interface for the NUM_IMAGES(TEAM) version. Also, your comment about using a team number of 0 to indicate the current team should go into a comment in the code rather than in the Phabricator review.

[craig.rasmussen]

Changed location of header file to flang/include/flang/Runtime/coarray.h.

[craig.rasmussen]

Added comments explaining why team_number=0 is a good default value when NUM_IMAGES is called without an actual argument for TEAM_NUMBER.

[PeteSteinfeld]

So far, so good.

As I commented earlier, I suspect that we'll need an additional interface to cover all forms of NUM_IMAGES().

[klausler]

flang/runtime/coarray.h

21 ↗

(On Diff #371727)

I think the default (team_number = 0) should work here because when forming a new team (11.6.9 FORM TEAM statement) the team_number has to be greater than 0. In 9.6 paragraph 3 the team number has to be from a FORM TEAM statement or be the initial team. In 16.9.189 TEAM_NUMBER paragraph 5 it states that the initial team shall have the value -1.

So team_number==0 isn't a valid team number and can represent NUM_IMAGES called with no actual arguments.

Or you could have two entry points, one with a team number and one without, and avoid exposing this kind of trick in the API. It could still be used as a hidden part of a common implementation.

[craig.rasmussen]

Peter Klausler wrote:

Or you could have two entry points, one with a team number and one without, and avoid exposing this kind of trick in the API. It could still be used as a hidden part of a common implementation.

I can revisit this when I add a TEAM type dummy (probably after you complete the type magic in the front end). For now this allows me to implement NUM_IMAGES for a single image. Possible function names: NumImages, NumImagesTeam NumImagesTeamNum.

As you say, the implementation can do whatever it wants.

-craig

From: Peter Klausler via Phabricator <[e-mail]>
Date: Monday, September 13, 2021 at 3:06 PM
To: Rasmussen, Craig E. <[e-mail]>, [e-mail] <[e-mail]>, [e-mail] <[e-mail]>, [e-mail] <[e-mail]>
Cc: [e-mail] <[e-mail]>
Subject: [PATCH] D109547: [flang] Add runtime interface for NUM_IMAGES
klausler added inline comments.

Comment at: flang/runtime/coarray.h:21
+// 16.9.145 NUM_IMAGES
+int RTNAME(NumImages)(int team_number = 0,

+ const char *sourceFile = nullptr, int sourceLine = 0);

craig.rasmussen wrote:

I think the default (team_number = 0) should work here because when forming a new team (11.6.9 FORM TEAM statement) the team_number has to be greater than 0. In 9.6 paragraph 3 the team number has to be from a FORM TEAM statement or be the initial team. In 16.9.189 TEAM_NUMBER paragraph 5 it states that the initial team shall have the value -1.

So team_number==0 isn't a valid team number and can represent NUM_IMAGES called with no actual arguments.
I think the default (team_number = 0) should work here because when forming a new team (11.6.9 FORM TEAM statement) the team_number has to be greater than 0. In 9.6 paragraph 3 the team number has to be from a FORM TEAM statement or be the initial team. In 16.9.189 TEAM_NUMBER paragraph 5 it states that the initial team shall have the value -1.

So team_number==0 isn't a valid team number and can represent NUM_IMAGES called with no actual arguments.

Or you could have two entry points, one with a team number and one without, and avoid exposing this kind of trick in the API. It could still be used as a hidden part of a common implementation.

CHANGES SINCE LAST ACTION

https://urldefense.us/v3/__https://reviews.llvm.org/D109547/new/__;!!G2kpM7uM-TzIFchu!neIxNJ4lJsWyAIvx6heTGuRQA6DGC8sGAzRI639eyb5fm7Gj4uXoj6rpMY6Nj4XCIU8K$<https://urldefense.us/v3/__https:/reviews.llvm.org/D109547/new/__;!!G2kpM7uM-TzIFchu!neIxNJ4lJsWyAIvx6heTGuRQA6DGC8sGAzRI639eyb5fm7Gj4uXoj6rpMY6Nj4XCIU8K$>

https://urldefense.us/v3/__https://reviews.llvm.org/D109547__;!!G2kpM7uM-TzIFchu!neIxNJ4lJsWyAIvx6heTGuRQA6DGC8sGAzRI639eyb5fm7Gj4uXoj6rpMY6Nj3z2uaZ1$https://urldefense.us/v3/__https:/reviews.llvm.org/D109547__;!!G2kpM7uM-TzIFchu!neIxNJ4lJsWyAIvx6heTGuRQA6DGC8sGAzRI639eyb5fm7Gj4uXoj6rpMY6Nj3z2uaZ1$

[craig.rasmussen]

Inlined call to Fortran::semantics::IsCoarray (one line change) to fix link error.

Also minor cleanup suggested by clang-format.

[craig.rasmussen]

Hopefully this will open the issue and is the correct way to correct a push that was reverted.

Note comment on line 97 of flang/include/flang/Evaluate/tools.h. This fixes link error for shared libraries.

flang/include/flang/Evaluate/tools.h

97 ↗

(On Diff #373090)

This line inlined from semantics::IsCoarray. This was only change needed to fix link error.

[PeteSteinfeld]

I did shared and non-shared builds, and both were successful.

flang/include/flang/Runtime/coarray.h

+//===-- include/flang/Runtime/coarray.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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_RUNTIME_COARRAY_H_
+#define FORTRAN_RUNTIME_COARRAY_H_
+
+// Defines API between compiled code and the coarray
+// support functions in the runtime library.
+
+#include "flang/Runtime/entry-names.h"
+
+namespace Fortran::runtime {
+
+extern "C" {
+// 16.9.145 NUM_IMAGES
+// The default value team_number=0 is not a valid team number and thus chosen
+// when NUM_IMAGES is called with no actual arguments, see:
+//   1. 9.6 paragraph 3: TEAM_NUMBER shall be from a FORM TEAM statement or
+//      the initial team.
+//   2. 16.9.189 TEAM_NUMBER paragraph 5: initial team shall have the value -1.
+//   3. 11.6.9 FORM TEAM statement: TEAM_NUMBER shall be greater than 0.
+int RTNAME(NumImages)(
+    int team_number = 0, const char *sourceFile = nullptr, int sourceLine = 0);
+}
+} // namespace Fortran::runtime
+
+#endif // FORTRAN_RUNTIME_COARRAY_H_