[flang][Driver] support -fno-openmp

[tblah]

Closes #83148

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-flang-driver

Author: Tom Eccles (tblah)

Changes

Closes #83148

---

Full diff: https://github.com/llvm/llvm-project/pull/107087.diff

4 Files Affected:

• (modified) clang/include/clang/Driver/Options.td (+1)
• (modified) flang/lib/Frontend/CompilerInvocation.cpp (+3-1)
• (added) flang/test/Driver/fno-openmp.f90 (+12)
• (modified) flang/test/Driver/fopenmp.f90 (+3)

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 83cf753e824845..8fe9f4f28f8fc1 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3545,6 +3545,7 @@ def fopenmp : Flag<["-"], "fopenmp">, Group<f_Group>,
   Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>,
   HelpText<"Parse OpenMP pragmas and generate parallel code.">;
 def fno_openmp : Flag<["-"], "fno-openmp">, Group<f_Group>,
+  Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>,
   Flags<[NoArgumentUnused]>;
 class OpenMPVersionHelp<string program, string default> {
   string str = !strconcat(
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 1d73397d330178..9e42fcc2e39d5e 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -968,7 +968,9 @@ static bool parseDialectArgs(CompilerInvocation &res, llvm::opt::ArgList &args,
 /// generated.
 static bool parseOpenMPArgs(CompilerInvocation &res, llvm::opt::ArgList &args,
                             clang::DiagnosticsEngine &diags) {
-  if (!args.hasArg(clang::driver::options::OPT_fopenmp))
+  llvm::opt::Arg *arg = args.getLastArg(clang::driver::options::OPT_fopenmp,
+                                        clang::driver::options::OPT_fno_openmp);
+  if (!arg || arg->getOption().matches(clang::driver::options::OPT_fno_openmp))
     return true;
 
   unsigned numErrorsBefore = diags.getNumErrors();
diff --git a/flang/test/Driver/fno-openmp.f90 b/flang/test/Driver/fno-openmp.f90
new file mode 100644
index 00000000000000..98c8793c8c9bce
--- /dev/null
+++ b/flang/test/Driver/fno-openmp.f90
@@ -0,0 +1,12 @@
+! RUN: %flang_fc1 -fopenmp -fno-openmp %s -emit-hlfir -o - | FileCheck --check-prefix=CHECK-NO-OMP %s
+! RUN: %flang_fc1 -fno-openmp %s -emit-hlfir -o - | FileCheck --check-prefix=CHECK-NO-OMP %s
+! RUN: %flang_fc1 -fno-openmp -fopenmp %s -emit-hlfir -o - | FileCheck --check-prefix=CHECK-OMP %s
+! RUN: %flang_fc1 -fopenmp %s -emit-hlfir -o - | FileCheck --check-prefix=CHECK-OMP %s
+
+subroutine main
+  ! CHECK-NO-OMP-NOT: omp.parallel
+  ! CHECK-OMP: omp.parallel
+  !$omp parallel
+  print *,"test"
+  !$omp end parallel
+end subroutine
diff --git a/flang/test/Driver/fopenmp.f90 b/flang/test/Driver/fopenmp.f90
index d70fe100c3d21b..b1c59e00302b61 100644
--- a/flang/test/Driver/fopenmp.f90
+++ b/flang/test/Driver/fopenmp.f90
@@ -11,6 +11,9 @@
 ! RUN: %flang -target x86_64-windows-gnu -fopenmp=libgomp -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-FC1-NO-OPENMP --check-prefix=CHECK-WARNING
 ! RUN: %flang -target x86_64-windows-gnu -fopenmp=libiomp5 -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-FC1-OPENMP
 
+!RUN: %flang -fno-openmp -fopenmp -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-FC1-OPENMP
+!RUN: %flang -fopenmp -fno-openmp -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-FC1-NO-OPENMP
+
 ! CHECK-FC1-OPENMP: "-fc1"
 ! CHECK-FC1-OPENMP: "-fopenmp"
 !

[pawosm-arm]

As I'm not seeing how linker is invoked, I just need to ask (for the sake of completeness) will it also prevent addition of -lomp to the linker's command line?

[tblah]

As I'm not seeing how linker is invoked, I just need to ask (for the sake of completeness) will it also prevent addition of -lomp to the linker's command line?

Thanks for pointing this out. I've added a test for the linker invocation.