Add -fprofile-sample-use to Clang's driver.

This adds a new option -fprofile-sample-use=filename to Clang. It
tells the driver to schedule the SampleProfileLoader pass and passes
on the name of the profile file to use.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194567 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 810e3c1..a4e4672 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -3074,6 +3074,13 @@
 
   // Forward -f options with positive and negative forms; we translate
   // these by hand.
+  if (Arg *A = Args.getLastArg(options::OPT_fprofile_sample_use_EQ)) {
+    StringRef fname = A->getValue();
+    if (!llvm::sys::fs::exists(fname))
+      D.Diag(diag::err_drv_no_such_file) << fname;
+    else
+      A->render(Args, CmdArgs);
+  }
 
   if (Args.hasArg(options::OPT_mkernel)) {
     if (!Args.hasArg(options::OPT_fapple_kext) && types::isCXX(InputType))