[XRay][clang] Add a flag to enable/disable linking XRay deps explicitly

Summary:
This change introduces `-fxray-link-deps` and `-fnoxray-link-deps`. The
`-fnoxray-link-deps` allows for directly controlling which specific XRay
runtime to link. The default is for clang to link the XRay runtime that
is shipped with the compiler (if there are any), but users may want to
explicitly add the XRay dependencies from other locations or other
means.

Reviewers: eizan, echristo, chandlerc

Reviewed By: eizan

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D45354

llvm-svn: 329376

4 files changed, 18 insertions, 1 deletions

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index c72bb39ec5c..9367634d8af 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1107,6 +1107,12 @@ def fxray_always_emit_customevents : Flag<["-"], "fxray-always-emit-customevents
 def fnoxray_always_emit_customevents : Flag<["-"], "fno-xray-always-emit-customevents">, Group<f_Group>,
   Flags<[CC1Option]>;
 
+def fxray_link_deps : Flag<["-"], "fxray-link-deps">, Group<f_Group>,
+  Flags<[CC1Option]>,
+  HelpText<"Tells clang to add the link dependencies for XRay.">;
+def fnoxray_link_deps : Flag<["-"], "fnoxray-link-deps">, Group<f_Group>,
+  Flags<[CC1Option]>;
+
 def ffine_grained_bitfield_accesses : Flag<["-"],
   "ffine-grained-bitfield-accesses">, Group<f_clang_Group>, Flags<[CC1Option]>,
   HelpText<"Use separate accesses for bitfields with legal widths and alignments.">;
diff --git a/clang/include/clang/Driver/XRayArgs.h b/clang/include/clang/Driver/XRayArgs.h
index b709ee4e87b..8eedd1dba1d 100644
--- a/clang/include/clang/Driver/XRayArgs.h
+++ b/clang/include/clang/Driver/XRayArgs.h
@@ -25,6 +25,7 @@ class XRayArgs {
   bool XRayInstrument = false;
   int InstructionThreshold = 200;
   bool XRayAlwaysEmitCustomEvents = false;
+  bool XRayRT = true;
 
 public:
   /// Parses the XRay arguments from an argument list.
@@ -32,7 +33,7 @@ public:
   void addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
                llvm::opt::ArgStringList &CmdArgs, types::ID InputType) const;
 
-  bool needsXRayRt() const { return XRayInstrument; }
+  bool needsXRayRt() const { return XRayInstrument && XRayRT; }
 };
 
 } // namespace driver
diff --git a/clang/lib/Driver/XRayArgs.cpp b/clang/lib/Driver/XRayArgs.cpp
index 19bf9b7d22c..e151cb907cd 100644
--- a/clang/lib/Driver/XRayArgs.cpp
+++ b/clang/lib/Driver/XRayArgs.cpp
@@ -76,6 +76,10 @@ XRayArgs::XRayArgs(const ToolChain &TC, const ArgList &Args) {
                      options::OPT_fnoxray_always_emit_customevents, false))
       XRayAlwaysEmitCustomEvents = true;
 
+    if (!Args.hasFlag(options::OPT_fxray_link_deps,
+                      options::OPT_fnoxray_link_deps, true))
+      XRayRT = false;
+
     // Validate the always/never attribute files. We also make sure that they
     // are treated as actual dependencies.
     for (const auto &Filename :
diff --git a/clang/test/Driver/XRay/xray-nolinkdeps.cpp b/clang/test/Driver/XRay/xray-nolinkdeps.cpp
new file mode 100644
index 00000000000..7f17c939a43
--- /dev/null
+++ b/clang/test/Driver/XRay/xray-nolinkdeps.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang -v -o /dev/null -fxray-instrument -fnoxray-link-deps %s -### \
+// RUN:     2>&1 | FileCheck --check-prefix DISABLE %s
+// RUN: %clang -v -o /dev/null -fxray-instrument -fxray-link-deps %s -### \
+// RUN:     2>&1 | FileCheck --check-prefix ENABLE %s
+// ENABLE: clang_rt.xray
+// DISABLE-NOT: clang_rt.xray