Factor out logic for finding the linker driver into a common function.

Author: martinboehme

include/swift/Driver/ToolChain.h

@@ -294,6 +294,9 @@ class ToolChain {
   void getClangLibraryPath(const llvm::opt::ArgList &Args,
                            SmallString<128> &LibPath) const;
 
+  // Returns the Clang driver executable to use for linking.
+  const char *getClangLinkerDriver(const llvm::opt::ArgList &Args) const;
+
   /// Returns the name the clang library for a given sanitizer would have on
   /// the current toolchain.
   ///

lib/Driver/ToolChains.cpp

@@ -1332,6 +1332,26 @@ void ToolChain::getRuntimeLibraryPaths(SmallVectorImpl<std::string> &runtimeLibP
   }
 }
 
+const char *ToolChain::getClangLinkerDriver(
+    const llvm::opt::ArgList &Args) const {
+  // We don't use `clang++` unconditionally because we want to avoid pulling in
+  // a C++ standard library if it's not needed, in particular because the
+  // standard library that `clang++` selects by default may not be the one that
+  // is desired.
+  const char *LinkerDriver =
+      Args.hasArg(options::OPT_enable_experimental_cxx_interop) ?
+      "clang++" : "clang";
+  if (const Arg *A = Args.getLastArg(options::OPT_tools_directory)) {
+    StringRef toolchainPath(A->getValue());
+
+    // If there is a linker driver in the toolchain folder, use that instead.
+    if (auto tool = llvm::sys::findProgramByName(LinkerDriver, {toolchainPath}))
+      LinkerDriver = Args.MakeArgString(tool.get());
+  }
+
+  return LinkerDriver;
+}
+
 bool ToolChain::sanitizerRuntimeLibExists(const ArgList &args,
                                           StringRef sanitizerName,
                                           bool shared) const {

lib/Driver/UnixToolChains.cpp

@@ -181,22 +181,9 @@ toolchains::GenericUnix::constructInvocation(const DynamicLinkJobAction &job,
   }
 
   // Configure the toolchain.
-  //
-  // We don't use `clang++` unconditionally because we want to avoid pulling in
-  // a C++ standard library if it's not needed, in particular because the
-  // standard library that `clang++` selects by default may not be the one that
-  // is desired.
-  const char *LinkerDriver =
-      context.Args.hasArg(options::OPT_enable_experimental_cxx_interop) ?
-      "clang++" : "clang";
   if (const Arg *A = context.Args.getLastArg(options::OPT_tools_directory)) {
     StringRef toolchainPath(A->getValue());
 
-    // If there is a linker driver in the toolchain folder, use that instead.
-    if (auto tool = llvm::sys::findProgramByName(LinkerDriver, {toolchainPath})) {
-      LinkerDriver = context.Args.MakeArgString(tool.get());
-    }
-
     // Look for binutils in the toolchain folder.
     Arguments.push_back("-B");
     Arguments.push_back(context.Args.MakeArgString(A->getValue()));
@@ -350,7 +337,7 @@ toolchains::GenericUnix::constructInvocation(const DynamicLinkJobAction &job,
   Arguments.push_back(
       context.Args.MakeArgString(context.Output.getPrimaryOutputFilename()));
 
-  InvocationInfo II{LinkerDriver, Arguments};
+  InvocationInfo II{getClangLinkerDriver(context.Args), Arguments};
   II.allowsResponseFiles = true;
 
   return II;

lib/Driver/WindowsToolChains.cpp

@@ -84,18 +84,6 @@ toolchains::Windows::constructInvocation(const DynamicLinkJobAction &job,
       Arguments.push_back("/DEBUG");
   }
 
-  // Configure the toolchain.
-  const char *LinkerDriver =
-      context.Args.hasArg(options::OPT_enable_experimental_cxx_interop) ?
-      "clang++" : "clang";
-  if (const Arg *A = context.Args.getLastArg(options::OPT_tools_directory)) {
-    StringRef toolchainPath(A->getValue());
-
-    // If there is a linker driver in the toolchain folder, use that instead.
-    if (auto tool = llvm::sys::findProgramByName(LinkerDriver, {toolchainPath}))
-      LinkerDriver = context.Args.MakeArgString(tool.get());
-  }
-
   // Rely on `-libc` to correctly identify the MSVC Runtime Library.  We use
   // `-nostartfiles` as that limits the difference to just the
   // `-defaultlib:libcmt` which is passed unconditionally with the `clang++`
@@ -189,7 +177,7 @@ toolchains::Windows::constructInvocation(const DynamicLinkJobAction &job,
   Arguments.push_back(
       context.Args.MakeArgString(context.Output.getPrimaryOutputFilename()));
 
-  InvocationInfo II{LinkerDriver, Arguments};
+  InvocationInfo II{getClangLinkerDriver(context.Args), Arguments};
   II.allowsResponseFiles = true;
 
   return II;