[FreeBSD] Support -stdlib=libstdc++

The experimental-library-flag.cpp test was failing on FreeBSD builders,
which turned to be caused by missing support for -stdlib=libcstdc++ (and
just using a hardcoded libc++ in all cases).
Simplify FreeBSD::AddCXXStdlibLibArgs() by deferring to the parent class
and dealing with the FreeSBD < 14 profiling support as a special case.

While touching the test file also drop the unnecessary `-o %t.o`. This is
not needed since the RUN lines use -### and don't produce any output.

Reviewed By: DimitryAndric, MaskRay

Pull Request: llvm/llvm-project#126302

(cherry picked from commit f75126e)

Author: arichardson

clang/lib/Driver/ToolChains/FreeBSD.cpp

@@ -479,12 +479,12 @@ void FreeBSD::addLibCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
 
 void FreeBSD::AddCXXStdlibLibArgs(const ArgList &Args,
                                   ArgStringList &CmdArgs) const {
+  Generic_ELF::AddCXXStdlibLibArgs(Args, CmdArgs);
   unsigned Major = getTriple().getOSMajorVersion();
-  bool Profiling = Args.hasArg(options::OPT_pg) && Major != 0 && Major < 14;
-
-  CmdArgs.push_back(Profiling ? "-lc++_p" : "-lc++");
-  if (Args.hasArg(options::OPT_fexperimental_library))
-    CmdArgs.push_back("-lc++experimental");
+  bool SuffixedLib = Args.hasArg(options::OPT_pg) && Major != 0 && Major < 14;
+  if (SuffixedLib && GetCXXStdlibType(Args) == CST_Libcxx)
+    llvm::replace(CmdArgs, static_cast<const char *>("-lc++"),
+                  static_cast<const char *>("-lc++_p"));
 }
 
 void FreeBSD::AddCudaIncludeArgs(const ArgList &DriverArgs,

clang/test/Driver/experimental-library-flag.cpp

@@ -9,6 +9,11 @@
 // RUN: %clangxx -fexperimental-library -stdlib=libstdc++ -### %s 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-LIBSTDCXX %s
 // RUN: %clangxx -fexperimental-library -stdlib=libc++ -nostdlib++ -### %s 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-NOSTDLIB %s
 
+/// The FreeBSD driver did not support -stdlib=libstdc++ previously, check that it does the right thing here.
+// RUN: %clangxx --target=x86_64-unknown-freebsd -fexperimental-library -stdlib=libc++ -### %s 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-LIBCXX %s
+// RUN: %clangxx --target=x86_64-unknown-freebsd -fexperimental-library -stdlib=libstdc++ -### %s 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-LIBSTDCXX %s
+// RUN: %clangxx --target=x86_64-unknown-freebsd -fexperimental-library -stdlib=libc++ -nostdlib++ -### %s 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-NOSTDLIB %s
+
 // -fexperimental-library must be passed to CC1.
 // CHECK: -fexperimental-library
 

clang/test/Driver/freebsd.cpp

@@ -1,15 +1,19 @@
-// RUN: %clangxx %s -### -o %t.o -target amd64-unknown-freebsd -stdlib=platform 2>&1 \
+// RUN: %clangxx %s -### --target=amd64-unknown-freebsd -stdlib=platform 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-DEFAULT %s
-// RUN: %clangxx %s -### -o %t.o -target amd64-unknown-freebsd10.0 -stdlib=platform 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-TEN %s
+// RUN: %clangxx %s -### --target=amd64-unknown-freebsd10.0 -stdlib=platform 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-DEFAULT %s
+// RUN: %clangxx %s -### --target=amd64-unknown-freebsd -stdlib=libc++ 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-DEFAULT %s
+// RUN: %clangxx %s -### --target=amd64-unknown-freebsd -stdlib=libstdc++ 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-STDLIBCXX %s
 // CHECK-DEFAULT: "-lc++" "-lm"
-// CHECK-TEN: "-lc++" "-lm"
+// CHECK-STDLIBCXX: "-lstdc++" "-lm"
 
-// RUN: %clangxx %s -### -pg -o %t.o -target amd64-unknown-freebsd -stdlib=platform 2>&1 \
+// RUN: %clangxx %s -### -pg --target=amd64-unknown-freebsd -stdlib=platform 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-PG-DEFAULT %s
-// RUN: %clangxx %s -### -pg -o %t.o -target amd64-unknown-freebsd14.0 -stdlib=platform 2>&1 \
+// RUN: %clangxx %s -### -pg --target=amd64-unknown-freebsd14.0 -stdlib=platform 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-PG-FOURTEEN %s
-// RUN: %clangxx %s -### -pg -o %t.o -target amd64-unknown-freebsd10.0 -stdlib=platform 2>&1 \
+// RUN: %clangxx %s -### -pg --target=amd64-unknown-freebsd10.0 -stdlib=platform 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-PG-TEN %s
 // CHECK-PG-DEFAULT: "-lc++" "-lm"
 // CHECK-PG-FOURTEEN: "-lc++" "-lm"