From a5efe3a66b9655a7f3ae6fa8d308455af3f50daa Mon Sep 17 00:00:00 2001
From: Bruno Cardoso Lopes <bruno.cardoso@gmail.com>
Date: Fri, 2 Oct 2015 15:10:33 +0000
Subject: [DarwinDriver] Reapply: Use -lto_library to specify the path for
 libLTO.dylib

Reapply r248935.

Usually, when using LTO with a clang installation newer than the
system's one, there's a libLTO.dylib version mismatch and LTO fails. One
solution to this is to make ld point to the right libLTO.dylib by
changing DYLD_LIBRARY_PATH.

However, ld64 supports specifying the complete path to the desired
libLTO.dylib through the -lto_library option. This commit adds support
for the clang driver to use this option whenever it's capable of finding
a libLTO.dylib in clang's installed library directory. This way, we
don't need to rely on DYLD_LIBRARY_PATH nor get caught by version
mismatches.

Differential Revision: http://reviews.llvm.org/D13117

rdar://problem/7363476

llvm-svn: 249143
---
 clang/lib/Driver/Tools.cpp | 37 ++++++++++++++++++++++++++++---------
 1 file changed, 28 insertions(+), 9 deletions(-)

(limited to 'clang/lib/Driver/Tools.cpp')

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 1b741ee8505..932122236b5 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -6502,15 +6502,34 @@ void darwin::Linker::AddLinkArgs(Compilation &C, const ArgList &Args,
                    options::OPT_fno_application_extension, false))
     CmdArgs.push_back("-application_extension");
 
-  // If we are using LTO, then automatically create a temporary file path for
-  // the linker to use, so that it's lifetime will extend past a possible
-  // dsymutil step.
-  if (Version[0] >= 116 && D.IsUsingLTO(Args) && NeedsTempPath(Inputs)) {
-    const char *TmpPath = C.getArgs().MakeArgString(
-        D.GetTemporaryPath("cc", types::getTypeTempSuffix(types::TY_Object)));
-    C.addTempFile(TmpPath);
-    CmdArgs.push_back("-object_path_lto");
-    CmdArgs.push_back(TmpPath);
+  if (D.IsUsingLTO(Args)) {
+    // If we are using LTO, then automatically create a temporary file path for
+    // the linker to use, so that it's lifetime will extend past a possible
+    // dsymutil step.
+    if (Version[0] >= 116 && NeedsTempPath(Inputs)) {
+      const char *TmpPath = C.getArgs().MakeArgString(
+          D.GetTemporaryPath("cc", types::getTypeTempSuffix(types::TY_Object)));
+      C.addTempFile(TmpPath);
+      CmdArgs.push_back("-object_path_lto");
+      CmdArgs.push_back(TmpPath);
+    }
+
+    // Use -lto_library option to specify the libLTO.dylib path. Try to find
+    // it in clang installed libraries. If not found, the option is not used
+    // and 'ld' will use its default mechanism to search for libLTO.dylib.
+    if (Version[0] >= 133) {
+      // Search for libLTO in <InstalledDir>/../lib/libLTO.dylib
+      StringRef P = llvm::sys::path::parent_path(D.getInstalledDir());
+      SmallString<128> LibLTOPath(P);
+      llvm::sys::path::append(LibLTOPath, "lib");
+      llvm::sys::path::append(LibLTOPath, "libLTO.dylib");
+      if (llvm::sys::fs::exists(LibLTOPath)) {
+        CmdArgs.push_back("-lto_library");
+        CmdArgs.push_back(C.getArgs().MakeArgString(LibLTOPath));
+      } else {
+        D.Diag(diag::warn_drv_lto_libpath);
+      }
+    }
   }
 
   // Derived from the "link" spec.
-- 
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