[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

4 files changed, 56 insertions, 9 deletions

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index f7f09da4ea6..c54d58a87a4 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -117,6 +117,8 @@ def err_drv_optimization_remark_pattern : Error<
 def err_drv_no_neon_modifier : Error<"[no]neon is not accepted as modifier, please use [no]simd instead">;
 
 def warn_O4_is_O3 : Warning<"-O4 is equivalent to -O3">, InGroup<Deprecated>;
+def warn_drv_lto_libpath : Warning<"libLTO.dylib relative to clang installed dir not found; using 'ld' default search path instead">,
+  InGroup<LibLTO>;
 def warn_drv_optimization_value : Warning<"optimization level '%0' is not supported; using '%1%2' instead">,
   InGroup<InvalidCommandLineArgument>;
 def warn_ignored_gcc_optimization : Warning<"optimization flag '%0' is not supported">,
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index a185b22519a..bf655cc3aa5 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -96,6 +96,7 @@ def Deprecated : DiagGroup<"deprecated", [DeprecatedDeclarations,
                                           DeprecatedWritableStr]>,
                  DiagCategory<"Deprecations">;
 
+def LibLTO : DiagGroup<"liblto">;
 def : DiagGroup<"disabled-optimization">;
 def : DiagGroup<"discard-qual">;
 def : DiagGroup<"div-by-zero">;
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.
diff --git a/clang/test/Driver/darwin-ld-lto.c b/clang/test/Driver/darwin-ld-lto.c
new file mode 100644
index 00000000000..23e006a0185
--- /dev/null
+++ b/clang/test/Driver/darwin-ld-lto.c
@@ -0,0 +1,25 @@
+// REQUIRES: system-darwin
+
+// Check that ld gets "-lto_library" and warnings about libLTO.dylib path.
+
+// RUN: %clang -target x86_64-apple-darwin10 -### %s \
+// RUN:   -mlinker-version=133 -flto 2> %t.log
+// RUN: cat %t.log
+// RUN: FileCheck -check-prefix=LINK_LTOLIB_PATH %s < %t.log
+//
+// LINK_LTOLIB_PATH: {{ld(.exe)?"}}
+// LINK_LTOLIB_PATH: "-lto_library"
+
+// RUN: %clang -target x86_64-apple-darwin10 -### %s \
+// RUN:   -ccc-install-dir %S/dummytestdir -mlinker-version=133 -flto 2> %t.log
+// RUN: cat %t.log
+// RUN: FileCheck -check-prefix=LINK_LTOLIB_PATH_WRN %s < %t.log
+//
+// LINK_LTOLIB_PATH_WRN: warning: libLTO.dylib relative to clang installed dir not found; using 'ld' default search path instead
+
+// RUN: %clang -target x86_64-apple-darwin10 -### %s \
+// RUN:   -ccc-install-dir %S/dummytestdir -mlinker-version=133 -Wno-liblto -flto 2> %t.log
+// RUN: cat %t.log
+// RUN: FileCheck -check-prefix=LINK_LTOLIB_PATH_NOWRN %s < %t.log
+//
+// LINK_LTOLIB_PATH_NOWRN-NOT: warning: libLTO.dylib relative to clang installed dir not found; using 'ld' default search path instead