Index: clang/lib/Driver/ToolChain.cpp
===================================================================
--- clang/lib/Driver/ToolChain.cpp
+++ clang/lib/Driver/ToolChain.cpp
@@ -22,6 +22,7 @@
 #include "clang/Driver/Options.h"
 #include "clang/Driver/SanitizerArgs.h"
 #include "clang/Driver/XRayArgs.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
@@ -413,12 +414,21 @@
   return std::string(Path.str());
 }
 
-static std::string buildCompilerRTBasename(const ToolChain &toolchain,
-                                           const ArgList &Args,
-                                           StringRef Component,
-                                           ToolChain::FileType Type,
-                                           bool AddArch) {
-  const llvm::Triple &TT = toolchain.getTriple();
+static Optional<std::string> findInLibraryPath(const ToolChain &TC,
+                                               StringRef filename) {
+  for (const auto &LibPath : TC.getLibraryPaths()) {
+    SmallString<128> P(LibPath);
+    llvm::sys::path::append(P, filename);
+    if (TC.getVFS().exists(P))
+      return std::string(P.str());
+  }
+  return llvm::None;
+}
+
+std::string ToolChain::getCompilerRTBasename(const ArgList &Args,
+                                             StringRef Component,
+                                             FileType Type) const {
+  const llvm::Triple &TT = getTriple();
   bool IsITANMSVCWindows =
       TT.isWindowsMSVCEnvironment() || TT.isWindowsItaniumEnvironment();
 
@@ -433,44 +443,35 @@
     Suffix = IsITANMSVCWindows ? ".lib" : ".a";
     break;
   case ToolChain::FT_Shared:
-    Suffix = TT.isOSWindows()
-                 ? (TT.isWindowsGNUEnvironment() ? ".dll.a" : ".lib")
+    Suffix = Triple.isOSWindows()
+                 ? (Triple.isWindowsGNUEnvironment() ? ".dll.a" : ".lib")
                  : ".so";
     break;
   }
 
-  std::string ArchAndEnv;
-  if (AddArch) {
-    StringRef Arch = getArchNameForCompilerRTLib(toolchain, Args);
-    const char *Env = TT.isAndroid() ? "-android" : "";
-    ArchAndEnv = ("-" + Arch + Env).str();
+  std::string CRTWithoutArch =
+      (Prefix + Twine("clang_rt.") + Component + Suffix).str();
+  if (findInLibraryPath(*this, CRTWithoutArch).hasValue()) {
+    return CRTWithoutArch;
   }
-  return (Prefix + Twine("clang_rt.") + Component + ArchAndEnv + Suffix).str();
-}
 
-std::string ToolChain::getCompilerRTBasename(const ArgList &Args,
-                                             StringRef Component,
-                                             FileType Type) const {
-  std::string absolutePath = getCompilerRT(Args, Component, Type);
-  return llvm::sys::path::filename(absolutePath).str();
+  StringRef Arch = getArchNameForCompilerRTLib(*this, Args);
+  const char *Env = TT.isAndroid() ? "-android" : "";
+  std::string ArchAndEnv = ("-" + Arch + Env).str();
+
+  return (Prefix + Twine("clang_rt.") + Component + ArchAndEnv + Suffix).str();
 }
 
 std::string ToolChain::getCompilerRT(const ArgList &Args, StringRef Component,
                                      FileType Type) const {
   // Check for runtime files in the new layout without the architecture first.
-  std::string CRTBasename =
-      buildCompilerRTBasename(*this, Args, Component, Type, /*AddArch=*/false);
-  for (const auto &LibPath : getLibraryPaths()) {
-    SmallString<128> P(LibPath);
-    llvm::sys::path::append(P, CRTBasename);
-    if (getVFS().exists(P))
-      return std::string(P.str());
+  std::string CRTBasename = getCompilerRTBasename(Args, Component, Type);
+  if (auto value = findInLibraryPath(*this, CRTBasename)) {
+    return value.getValue();
   }
 
   // Fall back to the old expected compiler-rt name if the new one does not
   // exist.
-  CRTBasename =
-      buildCompilerRTBasename(*this, Args, Component, Type, /*AddArch=*/true);
   SmallString<128> Path(getCompilerRTPath());
   llvm::sys::path::append(Path, CRTBasename);
   return std::string(Path.str());