As reported in https://llvm.org/bugs/show_bug.cgi?id=25496, on FreeBSD,
C++ programs compiled for profiling (using `-pg`) should be linked with
`-lc++_p` (or `-lstdc++_p`, depending on the `-stdlib=` setting), not
with the regular C++ libraries.

Add a `FreeBSD::AddCXXStdlibLibArgs()` override to handle this, and add
a test case for it.  While here, extend the test case for the proper
passing of -lm and -lm_p.

Reviewers: compnerd, davide, dws, emaste
Reviewed By: compnerd
Differential Revision: http://reviews.llvm.org/D16264

llvm-svn: 260851
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index cb5e732..ae24e47 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -3128,6 +3128,22 @@
   }
 }
 
+void FreeBSD::AddCXXStdlibLibArgs(const ArgList &Args,
+                                  ArgStringList &CmdArgs) const {
+  CXXStdlibType Type = GetCXXStdlibType(Args);
+  bool Profiling = Args.hasArg(options::OPT_pg);
+
+  switch (Type) {
+  case ToolChain::CST_Libcxx:
+    CmdArgs.push_back(Profiling ? "-lc++_p" : "-lc++");
+    break;
+
+  case ToolChain::CST_Libstdcxx:
+    CmdArgs.push_back(Profiling ? "-lstdc++_p" : "-lstdc++");
+    break;
+  }
+}
+
 Tool *FreeBSD::buildAssembler() const {
   return new tools::freebsd::Assembler(*this);
 }