[Flang][OpenMP] Add -fopenmp-force-usm option to flang (#94359)

This patch enables the `-fopenmp-force-usm` option to be passed to the
flang driver, which forwards it to the compiler frontend. This flag,
when set, results in the introduction of the `unified_shared_memory` bit
to the `omp.requires` attribute of the top-level module operation.

This is later combined with any other target device-related REQUIRES
clauses that may have been explicitly set in the compilation unit.

1 files changed, 3 insertions, 0 deletions

diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 50c3e8b..f64a939 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -906,6 +906,9 @@ static bool parseDialectArgs(CompilerInvocation &res, llvm::opt::ArgList &args,
             res.getLangOpts().OpenMPVersion, diags)) {
       res.getLangOpts().OpenMPVersion = Version;
     }
+    if (args.hasArg(clang::driver::options::OPT_fopenmp_force_usm)) {
+      res.getLangOpts().OpenMPForceUSM = 1;
+    }
     if (args.hasArg(clang::driver::options::OPT_fopenmp_is_target_device)) {
       res.getLangOpts().OpenMPIsTargetDevice = 1;