https://github.com/DavidTruby created
https://github.com/llvm/llvm-project/pull/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.
>From 1f039de4e91c052033bed2ecab1ac0fe101ffeea Mon Sep 17 00:00:00 2001
From: David Truby <david.tr...@arm.com>
Date: Mon, 14 Oct 2024 14:39:44 +0100
Subject: [PATCH] [flang] Link to libatomic with openmp and rtlib=libgcc
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.
---
clang/lib/Driver/ToolChains/CommonArgs.cpp | 10 ++++++++++
flang/test/Driver/atomic.f90 | 5 +++++
2 files changed, 15 insertions(+)
create mode 100644 flang/test/Driver/atomic.f90
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp
b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 0c6a585c3acffd..7f9fc3559fcbd8 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..4d3ba89be27580
--- /dev/null
+++ b/flang/test/Driver/atomic.f90
@@ -0,0 +1,5 @@
+!RUN: %flang -fopenmp -rtlib=libgcc -### %s 2>&1 | FileCheck
--check-prefixes=GCC %s
+!RUN: %flang -fopenmp -rtlib=compiler-rt -### %s 2>&1 | FileCheck
--check-prefixes=CRT %s
+
+!GCC: -latomic
+!CRT-NOT: -latomic
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