[Driver] Add support for -fno-builtin-foo options.

Addresses PR4941 and rdar://6756912.
http://reviews.llvm.org/D15195

llvm-svn: 256937

1 files changed, 25 insertions, 3 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 7923b83..8468105 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -4740,11 +4740,33 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       A->render(Args, CmdArgs);
   }
 
-  // -fbuiltin is default unless -mkernel is used
-  if (!Args.hasFlag(options::OPT_fbuiltin, options::OPT_fno_builtin,
-                    !Args.hasArg(options::OPT_mkernel)))
+  // -fbuiltin is default unless -mkernel is used.
+  bool UseBuiltins =
+      Args.hasFlag(options::OPT_fbuiltin, options::OPT_fno_builtin,
+                   !Args.hasArg(options::OPT_mkernel));
+  if (!UseBuiltins)
     CmdArgs.push_back("-fno-builtin");
 
+  // -ffreestanding implies -fno-builtin.
+  if (Args.hasArg(options::OPT_ffreestanding))
+    UseBuiltins = false;
+
+  // Process the -fno-builtin-* options.
+  for (const auto &Arg : Args) {
+    const Option &O = Arg->getOption();
+    if (!O.matches(options::OPT_fno_builtin_))
+      continue;
+
+    Arg->claim();
+    // If -fno-builtin is specified, then there's no need to pass the option to
+    // the frontend.
+    if (!UseBuiltins)
+      continue;
+
+    StringRef FuncName = Arg->getValue();
+    CmdArgs.push_back(Args.MakeArgString("-fno-builtin-" + FuncName));
+  }
+
   if (!Args.hasFlag(options::OPT_fassume_sane_operator_new,
                     options::OPT_fno_assume_sane_operator_new))
     CmdArgs.push_back("-fno-assume-sane-operator-new");