[clang] ab2b175 - [flang] Link to libatomic with openmp and rtlib=libgcc (#112202)

[via cfe-commits]

Author: David Truby
Date: 2024-10-16T14:48:59+01:00
New Revision: ab2b17512cda90305d5bea77b8e8fa119ab78f25

URL: https://github.com/llvm/llvm-project/commit/ab2b17512cda90305d5bea77b8e8fa119ab78f25
DIFF: https://github.com/llvm/llvm-project/commit/ab2b17512cda90305d5bea77b8e8fa119ab78f25.diff

LOG: [flang] Link to libatomic with openmp and rtlib=libgcc (#112202)

Currently when using OpenMP atomics we depend on some symbols from
libatomic. These symbols are provided in a separate library for the
libgcc runtime, so we should link to that when rtlib=libgcc.

For the compiler-rt case, the presence and location of the symbols is
dependent on how compiler-rt itself was built so we cannot make that
decision for the user. As such no extra flags are added in that case.

Added: 
    flang/test/Driver/atomic.f90

Modified: 
    clang/lib/Driver/ToolChains/CommonArgs.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 3dd86ab7b99ca9..e662c3f0d2fa8f 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -1294,6 +1294,16 @@ void tools::addFortranRuntimeLibs(const ToolChain &TC, const ArgList &Args,
     CmdArgs.push_back("-lFortranRuntime");
     CmdArgs.push_back("-lFortranDecimal");
   }
+
+  // libomp needs libatomic for atomic operations if using libgcc
+  if (Args.hasFlag(options::OPT_fopenmp, options::OPT_fopenmp_EQ,
+                   options::OPT_fno_openmp, false)) {
+    Driver::OpenMPRuntimeKind OMPRuntime =
+        TC.getDriver().getOpenMPRuntime(Args);
+    ToolChain::RuntimeLibType RuntimeLib = TC.GetRuntimeLibType(Args);
+    if (OMPRuntime == Driver::OMPRT_OMP && RuntimeLib == ToolChain::RLT_Libgcc)
+      CmdArgs.push_back("-latomic");
+  }
 }
 
 void tools::addFortranRuntimeLibraryPath(const ToolChain &TC,

diff  --git a/flang/test/Driver/atomic.f90 b/flang/test/Driver/atomic.f90
new file mode 100644
index 00000000000000..0fb3b428f694c1
--- /dev/null
+++ b/flang/test/Driver/atomic.f90
@@ -0,0 +1,5 @@
+!RUN: %flang --target=aarch64-unknown-linux-gnu -fuse-ld=ld -fopenmp -rtlib=libgcc -### %s 2>&1 | FileCheck --check-prefixes=GCC %s
+!RUN: %flang --target=aarch64-unknown-linux-gnu -fuse-ld=ld -fopenmp -rtlib=compiler-rt -### %s 2>&1 | FileCheck --check-prefixes=CRT %s
+
+!GCC: -latomic
+!CRT-NOT: -latomic