Index: cfe/trunk/docs/ReleaseNotes.rst
===================================================================
--- cfe/trunk/docs/ReleaseNotes.rst
+++ cfe/trunk/docs/ReleaseNotes.rst
@@ -77,7 +77,10 @@
 
 - `clang -dumpversion` now returns the version of Clang itself.
 
-- ...
+- On ELF, ``-gz`` now defaults to ``-gz=zlib``. It produces ``SHF_COMPRESSED``
+  style compression of debug information. GNU binutils 2.26 or newer, or lld is
+  required to link produced object files. Use ``-gz=zlib-gnu`` to get the old
+  behavior.
 
 New Pragmas in Clang
 --------------------
Index: cfe/trunk/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- cfe/trunk/lib/Frontend/CompilerInvocation.cpp
+++ cfe/trunk/lib/Frontend/CompilerInvocation.cpp
@@ -1052,8 +1052,7 @@
   if (const Arg *A = Args.getLastArg(OPT_compress_debug_sections,
                                      OPT_compress_debug_sections_EQ)) {
     if (A->getOption().getID() == OPT_compress_debug_sections) {
-      // TODO: be more clever about the compression type auto-detection
-      Opts.setCompressDebugSections(llvm::DebugCompressionType::GNU);
+      Opts.setCompressDebugSections(llvm::DebugCompressionType::Z);
     } else {
       auto DCT = llvm::StringSwitch<llvm::DebugCompressionType>(A->getValue())
                      .Case("none", llvm::DebugCompressionType::None)
Index: cfe/trunk/tools/driver/cc1as_main.cpp
===================================================================
--- cfe/trunk/tools/driver/cc1as_main.cpp
+++ cfe/trunk/tools/driver/cc1as_main.cpp
@@ -221,8 +221,7 @@
   if (const Arg *A = Args.getLastArg(OPT_compress_debug_sections,
                                      OPT_compress_debug_sections_EQ)) {
     if (A->getOption().getID() == OPT_compress_debug_sections) {
-      // TODO: be more clever about the compression type auto-detection
-      Opts.CompressDebugSections = llvm::DebugCompressionType::GNU;
+      Opts.CompressDebugSections = llvm::DebugCompressionType::Z;
     } else {
       Opts.CompressDebugSections =
           llvm::StringSwitch<llvm::DebugCompressionType>(A->getValue())