1 files changed, 51 insertions, 32 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 28cb4df..f5b6bd8 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -7806,6 +7806,50 @@ static void addSanitizerRTWindows(const ToolChain &TC, const ArgList &Args,
   CmdArgs.push_back(Args.MakeArgString(LibSanitizer));
 }
 
+// Try to find Exe from a Visual Studio distribution.  This first tries to find
+// an installed copy of Visual Studio and, failing that, looks in the PATH,
+// making sure that whatever executable that's found is not a same-named exe
+// from clang itself to prevent clang from falling back to itself.
+static std::string FindVisualStudioExecutable(const ToolChain &TC,
+                                              const char *Exe,
+                                              const char *ClangProgramPath) {
+  // Since a particular Visual Studio executable is tied to a set of system
+  // includes and libraries, first try to use the same location that we use for
+  // the include paths to ensure that a consistent build environment is located.
+  const toolchains::Windows &WTC = static_cast<const toolchains::Windows &>(TC);
+  std::string visualStudioDir;
+  if (WTC.getVisualStudioDir(visualStudioDir)) {
+    SmallString<128> VSDir(visualStudioDir);
+    llvm::sys::path::append(VSDir, "VC\\bin");
+    llvm::sys::path::append(VSDir, Exe);
+    if (llvm::sys::fs::can_execute(VSDir.c_str()))
+      return VSDir.str();
+  }
+
+  // If it could not be found, we're already probably broken, but try to
+  // fallback to PATH anyway.
+  llvm::Optional<std::string> OptPath = llvm::sys::Process::GetEnv("PATH");
+  if (!OptPath.hasValue())
+    return Exe;
+
+  const char EnvPathSeparatorStr[] = {llvm::sys::EnvPathSeparator, '\0'};
+  SmallVector<StringRef, 8> PathSegments;
+  llvm::SplitString(OptPath.getValue(), PathSegments, EnvPathSeparatorStr);
+
+  for (StringRef PathSegment : PathSegments) {
+    if (PathSegment.empty())
+      continue;
+
+    SmallString<128> FilePath(PathSegment);
+    llvm::sys::path::append(FilePath, Exe);
+    if (llvm::sys::fs::can_execute(FilePath.c_str()) &&
+        !llvm::sys::fs::equivalent(FilePath.c_str(), ClangProgramPath))
+      return FilePath.str();
+  }
+
+  return Exe;
+}
+
 void visualstudio::Link::ConstructJob(Compilation &C, const JobAction &JA,
                                       const InputInfo &Output,
                                       const InputInfoList &Inputs,
@@ -7891,8 +7935,11 @@ void visualstudio::Link::ConstructJob(Compilation &C, const JobAction &JA,
     A.renderAsInput(Args, CmdArgs);
   }
 
-  const char *Exec =
-    Args.MakeArgString(getToolChain().GetProgramPath("link.exe"));
+  // It's not sufficient to just use link from the program PATH, because other
+  // environments like GnuWin32 install their own link.exe which may come first.
+  llvm::SmallString<128> linkPath(FindVisualStudioExecutable(
+      getToolChain(), "link.exe", C.getDriver().getClangProgramPath()));
+  const char *Exec = Args.MakeArgString(linkPath);
   C.addCommand(llvm::make_unique<Command>(JA, *this, Exec, CmdArgs));
 }
 
@@ -7904,35 +7951,6 @@ void visualstudio::Compile::ConstructJob(Compilation &C, const JobAction &JA,
   C.addCommand(GetCommand(C, JA, Output, Inputs, Args, LinkingOutput));
 }
 
-// Try to find FallbackName on PATH that is not identical to ClangProgramPath.
-// If one cannot be found, return FallbackName.
-// We do this special search to prevent clang-cl from falling back onto itself
-// if it's available as cl.exe on the path.
-static std::string FindFallback(const char *FallbackName,
-                                const char *ClangProgramPath) {
-  llvm::Optional<std::string> OptPath = llvm::sys::Process::GetEnv("PATH");
-  if (!OptPath.hasValue())
-    return FallbackName;
-
-  const char EnvPathSeparatorStr[] = {llvm::sys::EnvPathSeparator, '\0'};
-  SmallVector<StringRef, 8> PathSegments;
-  llvm::SplitString(OptPath.getValue(), PathSegments, EnvPathSeparatorStr);
-
-  for (size_t i = 0, e = PathSegments.size(); i != e; ++i) {
-    StringRef PathSegment = PathSegments[i];
-    if (PathSegment.empty())
-      continue;
-
-    SmallString<128> FilePath(PathSegment);
-    llvm::sys::path::append(FilePath, FallbackName);
-    if (llvm::sys::fs::can_execute(Twine(FilePath)) &&
-        !llvm::sys::fs::equivalent(Twine(FilePath), ClangProgramPath))
-      return FilePath.str();
-  }
-
-  return FallbackName;
-}
-
 std::unique_ptr<Command> visualstudio::Compile::GetCommand(
     Compilation &C, const JobAction &JA, const InputInfo &Output,
     const InputInfoList &Inputs, const ArgList &Args,
@@ -8014,7 +8032,8 @@ std::unique_ptr<Command> visualstudio::Compile::GetCommand(
   CmdArgs.push_back(Fo);
 
   const Driver &D = getToolChain().getDriver();
-  std::string Exec = FindFallback("cl.exe", D.getClangProgramPath());
+  std::string Exec = FindVisualStudioExecutable(getToolChain(), "cl.exe",
+                                                D.getClangProgramPath());
   return llvm::make_unique<Command>(JA, *this, Args.MakeArgString(Exec),
                                     CmdArgs);
 }