[LTO] Merge r287685 into the 3.9.1 branch, darwin: Unconditionally pass -lto_library, remove -Wliblto warning.

See: https://llvm.org/bugs/PR31120
llvm-svn: 287784

3 files changed, 12 insertions, 22 deletions

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 6b8db6963daa..0a9b34827dc2 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -159,8 +159,6 @@ def err_drv_bitcode_unsupported_on_toolchain : Error<
   "-fembed-bitcode is not supported on versions of iOS prior to 6.0">;
 
 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/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 0795b152c690..270ed0a4e756 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -7640,20 +7640,20 @@ void darwin::Linker::AddLinkArgs(Compilation &C, const ArgList &Args,
   }
 
   // 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.
+  // it in clang installed libraries. ld64 will only look at this argument
+  // when it actually uses LTO, so libLTO.dylib only needs to exist at link
+  // time if ld64 decides that it needs to use LTO.
+  // Since this is passed unconditionally, ld64 will never look for libLTO.dylib
+  // next to it. That's ok since ld64 using a libLTO.dylib not matching the
+  // clang version won't work anyways.
   if (Version[0] >= 133) {
     // Search for libLTO in <InstalledDir>/../lib/libLTO.dylib
     StringRef P = llvm::sys::path::parent_path(D.Dir);
     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);
-    }
+    CmdArgs.push_back("-lto_library");
+    CmdArgs.push_back(C.getArgs().MakeArgString(LibLTOPath));
   }
 
   // Derived from the "link" spec.
diff --git a/clang/test/Driver/darwin-ld-lto.c b/clang/test/Driver/darwin-ld-lto.c
index d244f988df73..6b9b79bd011a 100644
--- a/clang/test/Driver/darwin-ld-lto.c
+++ b/clang/test/Driver/darwin-ld-lto.c
@@ -1,6 +1,6 @@
 // REQUIRES: system-darwin
 
-// Check that ld gets "-lto_library" and warnings about libLTO.dylib path.
+// Check that ld gets "-lto_library".
 
 // RUN: %clang -target x86_64-apple-darwin10 -### %s \
 // RUN:   -ccc-install-dir %T/bin -mlinker-version=133 2> %t.log
@@ -9,16 +9,8 @@
 // LINK_LTOLIB_PATH: {{ld(.exe)?"}}
 // LINK_LTOLIB_PATH: "-lto_library"
 
+// Also pass -lto_library even if the file doesn't exist; if it's needed at
+// link time, ld will complain instead.
 // RUN: %clang -target x86_64-apple-darwin10 -### %s \
 // RUN:   -ccc-install-dir %S/dummytestdir -mlinker-version=133 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 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
+// RUN: FileCheck -check-prefix=LINK_LTOLIB_PATH %s -input-file %t.log