[flang][OpenMP] Remove experimental warning #144915

tblah · 2025-06-19T15:30:40Z

RFC: https://discourse.llvm.org/t/rfc-removing-the-openmp-experimental-warning-for-llvm-21/86455

There are a handful of open issues still to resolve before this can go out of draft. See the linked issue.

bhandarkar-pranav

LGTM. I have a nit, but too minor to warrant an update to this PR. Only address it if you are planning to push an update to this PR on account of someone else's review with beefier changes requested.

bhandarkar-pranav · 2025-06-19T15:56:04Z

flang/test/Driver/fopenmp.f90

@@ -74,6 +74,6 @@
 ! CHECK-LD-ANYMD: "{{.*}}ld{{(.exe)?}}"
 ! CHECK-LD-ANYMD: "-l{{(omp|gomp|iomp5md)}}"
 !
-! RUN: %flang -fopenmp -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-EXPERIMENTAL
+! RUN: %flang -fopenmp -fopenmp-version=40 -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-EXPERIMENTAL


NIT: sed 's/EXPERIMENTAL/INCOMPLETE/g'

NimishMishra

LGTM. Thanks a lot

kparzysz

LGTM

llvmbot · 2025-06-25T12:45:49Z

@llvm/pr-subscribers-clang-driver

@llvm/pr-subscribers-clang

Author: Tom Eccles (tblah)

Changes

RFC: https://discourse.llvm.org/t/rfc-removing-the-openmp-experimental-warning-for-llvm-21/86455

Fixes: #110008

There are a handful of open issues still to resolve before this can go out of draft. See the linked issue.

Full diff: https://github.com/llvm/llvm-project/pull/144915.diff

3 Files Affected:

(modified) clang/include/clang/Basic/DiagnosticDriverKinds.td (+2-2)
(modified) clang/lib/Driver/ToolChains/Flang.cpp (+16-3)
(modified) flang/test/Driver/fopenmp.f90 (+2-2)

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 29f6480ba935c..68f87ebb1b39f 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -143,8 +143,8 @@ def warn_drv_unsupported_option_for_processor : Warning<
 def warn_drv_unsupported_openmp_library : Warning<
   "the library '%0=%1' is not supported, OpenMP will not be enabled">,
   InGroup<OptionIgnored>;
-def warn_openmp_experimental : Warning<
-  "OpenMP support in flang is still experimental">,
+def warn_openmp_incomplete : Warning<
+  "OpenMP support for version %0 in flang is still incomplete">,
   InGroup<ExperimentalOption>;
 
 def err_drv_invalid_thread_model_for_target : Error<
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 47d0e345086b2..04613457cb20a 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -11,6 +11,7 @@
 
 #include "clang/Basic/CodeGenOptions.h"
 #include "clang/Driver/CommonArgs.h"
+#include "clang/Driver/OptionUtils.h"
 #include "clang/Driver/Options.h"
 #include "llvm/Frontend/Debug/Options.h"
 #include "llvm/Support/Path.h"
@@ -772,6 +773,13 @@ static void renderRemarksOptions(const ArgList &Args, ArgStringList &CmdArgs,
   }
 }
 
+static std::string OpenMPVersionToString(int Version) {
+  int Major = Version / 10;
+  int Minor = Version % 10;
+
+  return llvm::Twine{Major}.concat(".").concat(llvm::Twine{Minor}).str();
+}
+
 void Flang::ConstructJob(Compilation &C, const JobAction &JA,
                          const InputInfo &Output, const InputInfoList &Inputs,
                          const ArgList &Args, const char *LinkingOutput) const {
@@ -906,9 +914,14 @@ void Flang::ConstructJob(Compilation &C, const JobAction &JA,
 
       if (Args.hasArg(options::OPT_fopenmp_force_usm))
         CmdArgs.push_back("-fopenmp-force-usm");
-      // TODO: OpenMP support isn't "done" yet, so for now we warn that it
-      // is experimental.
-      D.Diag(diag::warn_openmp_experimental);
+
+      // TODO: OpenMP support for newer versions of the standard is incomplete.
+      if (int Version =
+              getLastArgIntValue(Args, options::OPT_fopenmp_version_EQ, 0)) {
+        if (Version >= 40)
+          D.Diag(diag::warn_openmp_incomplete)
+              << OpenMPVersionToString(Version);
+      }
 
       // FIXME: Clang supports a whole bunch more flags here.
       break;
diff --git a/flang/test/Driver/fopenmp.f90 b/flang/test/Driver/fopenmp.f90
index b3c3547800bdb..3a150aa657953 100644
--- a/flang/test/Driver/fopenmp.f90
+++ b/flang/test/Driver/fopenmp.f90
@@ -74,6 +74,6 @@
 ! CHECK-LD-ANYMD: "{{.*}}ld{{(.exe)?}}"
 ! CHECK-LD-ANYMD: "-l{{(omp|gomp|iomp5md)}}"
 !
-! RUN: %flang -fopenmp -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-EXPERIMENTAL
+! RUN: %flang -fopenmp -fopenmp-version=40 -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-INCOMPLETE
 !
-! CHECK-EXPERIMENTAL: flang{{.*}}: warning: OpenMP support in flang is still experimental
+! CHECK-INCOMPLETE: flang{{.*}}: warning: OpenMP support for version 4.0 in flang is still incomplete

llvmbot · 2025-06-25T12:45:50Z

@llvm/pr-subscribers-flang-driver

Author: Tom Eccles (tblah)

Changes

RFC: https://discourse.llvm.org/t/rfc-removing-the-openmp-experimental-warning-for-llvm-21/86455

Fixes: #110008

There are a handful of open issues still to resolve before this can go out of draft. See the linked issue.

Full diff: https://github.com/llvm/llvm-project/pull/144915.diff

3 Files Affected:

(modified) clang/include/clang/Basic/DiagnosticDriverKinds.td (+2-2)
(modified) clang/lib/Driver/ToolChains/Flang.cpp (+16-3)
(modified) flang/test/Driver/fopenmp.f90 (+2-2)

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 29f6480ba935c..68f87ebb1b39f 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -143,8 +143,8 @@ def warn_drv_unsupported_option_for_processor : Warning<
 def warn_drv_unsupported_openmp_library : Warning<
   "the library '%0=%1' is not supported, OpenMP will not be enabled">,
   InGroup<OptionIgnored>;
-def warn_openmp_experimental : Warning<
-  "OpenMP support in flang is still experimental">,
+def warn_openmp_incomplete : Warning<
+  "OpenMP support for version %0 in flang is still incomplete">,
   InGroup<ExperimentalOption>;
 
 def err_drv_invalid_thread_model_for_target : Error<
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 47d0e345086b2..04613457cb20a 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -11,6 +11,7 @@
 
 #include "clang/Basic/CodeGenOptions.h"
 #include "clang/Driver/CommonArgs.h"
+#include "clang/Driver/OptionUtils.h"
 #include "clang/Driver/Options.h"
 #include "llvm/Frontend/Debug/Options.h"
 #include "llvm/Support/Path.h"
@@ -772,6 +773,13 @@ static void renderRemarksOptions(const ArgList &Args, ArgStringList &CmdArgs,
   }
 }
 
+static std::string OpenMPVersionToString(int Version) {
+  int Major = Version / 10;
+  int Minor = Version % 10;
+
+  return llvm::Twine{Major}.concat(".").concat(llvm::Twine{Minor}).str();
+}
+
 void Flang::ConstructJob(Compilation &C, const JobAction &JA,
                          const InputInfo &Output, const InputInfoList &Inputs,
                          const ArgList &Args, const char *LinkingOutput) const {
@@ -906,9 +914,14 @@ void Flang::ConstructJob(Compilation &C, const JobAction &JA,
 
       if (Args.hasArg(options::OPT_fopenmp_force_usm))
         CmdArgs.push_back("-fopenmp-force-usm");
-      // TODO: OpenMP support isn't "done" yet, so for now we warn that it
-      // is experimental.
-      D.Diag(diag::warn_openmp_experimental);
+
+      // TODO: OpenMP support for newer versions of the standard is incomplete.
+      if (int Version =
+              getLastArgIntValue(Args, options::OPT_fopenmp_version_EQ, 0)) {
+        if (Version >= 40)
+          D.Diag(diag::warn_openmp_incomplete)
+              << OpenMPVersionToString(Version);
+      }
 
       // FIXME: Clang supports a whole bunch more flags here.
       break;
diff --git a/flang/test/Driver/fopenmp.f90 b/flang/test/Driver/fopenmp.f90
index b3c3547800bdb..3a150aa657953 100644
--- a/flang/test/Driver/fopenmp.f90
+++ b/flang/test/Driver/fopenmp.f90
@@ -74,6 +74,6 @@
 ! CHECK-LD-ANYMD: "{{.*}}ld{{(.exe)?}}"
 ! CHECK-LD-ANYMD: "-l{{(omp|gomp|iomp5md)}}"
 !
-! RUN: %flang -fopenmp -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-EXPERIMENTAL
+! RUN: %flang -fopenmp -fopenmp-version=40 -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-INCOMPLETE
 !
-! CHECK-EXPERIMENTAL: flang{{.*}}: warning: OpenMP support in flang is still experimental
+! CHECK-INCOMPLETE: flang{{.*}}: warning: OpenMP support for version 4.0 in flang is still incomplete

tblah · 2025-06-25T13:00:30Z

I've taken this out of draft.

The only remaining item in #110008 is some improved semantic checks for Loop transformation constructs. The parsing of these constructs works already and a TODO is emitted, but semantic checks should be updated to allow loop transformation constructs in place of Fortran do loops e.g.

!$omp parallel do
!$omp unroll
do i = 1, N
...

@Stylie777 is already working on this, but his work could conflict with #143715 and #144785 he will likely base his patch upon that other work and post after they are merged.

I would like to go ahead and merge this now because the loop transformation constructs are an OpenMP 5.1 feature and they do not lead to a compiler crash, only a misleading semantic error.

Is everyone okay with this being merged?

NimishMishra · 2025-06-25T13:02:16Z

I would like to go ahead and merge this now because the loop transformation constructs are an OpenMP 5.1 feature and they do not lead to a compiler crash, only a misleading semantic error.

I am okay with it.

tarunprabhu

Thanks Tom. I'm fine with merging this.

RFC: https://discourse.llvm.org/t/rfc-removing-the-openmp-experimental-warning-for-llvm-21/86455 Fixes: llvm#110008

tblah · 2025-06-26T10:33:44Z

ebd2980 moves the warning to the frontend driver so it can use the checks added in #145725

RFC: https://discourse.llvm.org/t/rfc-removing-the-openmp-experimental-warning-for-llvm-21/86455 Fixes: llvm#110008

tblah requested review from kiranchandramohan, jdoerfert, NimishMishra, kparzysz and bhandarkar-pranav June 19, 2025 15:30

bhandarkar-pranav approved these changes Jun 19, 2025

View reviewed changes

NimishMishra approved these changes Jun 20, 2025

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kparzysz approved these changes Jun 20, 2025

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tblah changed the title ~~DRAFT: [flang][OpenMP] Remove experimental warning~~ [flang][OpenMP] Remove experimental warning Jun 25, 2025

tblah marked this pull request as ready for review June 25, 2025 12:45

llvmbot added clang Clang issues not falling into any other category clang:driver 'clang' and 'clang++' user-facing binaries. Not 'clang-cl' clang:frontend Language frontend issues, e.g. anything involving "Sema" flang:driver flang Flang issues not falling into any other category labels Jun 25, 2025

tarunprabhu approved these changes Jun 25, 2025

View reviewed changes

tblah mentioned this pull request Jun 25, 2025

[flang][OpenMP] Verify that N in -fopenmp-version=N is valid #145725

Merged

tblah added 3 commits June 26, 2025 09:24

[flang][OpenMP] Remove experimental warning

7bb96a8

RFC: https://discourse.llvm.org/t/rfc-removing-the-openmp-experimental-warning-for-llvm-21/86455 Fixes: llvm#110008

s/EXPERIMENTAL/INCOMPLETE/

5af1bfb

Move warning to frontend driver

ebd2980

tblah force-pushed the ecclescake/experimental-warning branch from 172de0a to ebd2980 Compare June 26, 2025 10:32

kparzysz approved these changes Jun 26, 2025

View reviewed changes

mrkajetanp approved these changes Jun 26, 2025

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tblah merged commit cc1eae6 into llvm:main Jun 26, 2025
7 checks passed

anthonyhatran pushed a commit to anthonyhatran/llvm-project that referenced this pull request Jun 26, 2025

[flang][OpenMP] Remove experimental warning (llvm#144915)

30204bc

RFC: https://discourse.llvm.org/t/rfc-removing-the-openmp-experimental-warning-for-llvm-21/86455 Fixes: llvm#110008

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