diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index 4d438c2..b1b866c 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -289,6 +289,14 @@
   CmdArgs.push_back(Args.MakeArgString(P));
 }
 
+unsigned DarwinClang::GetDefaultDwarfVersion() const {
+  // Default to use DWARF 2 on OS X 10.10 / iOS 8 and lower.
+  if ((isTargetMacOS() && isMacosxVersionLT(10, 11)) ||
+      (isTargetIOSBased() && isIPhoneOSVersionLT(9)))
+    return 2;
+  return 4;
+}
+
 void MachO::AddLinkRuntimeLib(const ArgList &Args, ArgStringList &CmdArgs,
                               StringRef DarwinLibName, bool AlwaysLink,
                               bool IsEmbedded, bool AddRPath) const {
diff --git a/lib/Driver/ToolChains.h b/lib/Driver/ToolChains.h
index c636e39..f33317a 100644
--- a/lib/Driver/ToolChains.h
+++ b/lib/Driver/ToolChains.h
@@ -585,7 +585,7 @@
   void AddLinkARCArgs(const llvm::opt::ArgList &Args,
                       llvm::opt::ArgStringList &CmdArgs) const override;
 
-  unsigned GetDefaultDwarfVersion() const override { return 4; }
+  unsigned GetDefaultDwarfVersion() const override;
   // Until dtrace (via CTF) and LLDB can deal with distributed debug info,
   // Darwin defaults to standalone/full debug info.
   bool GetDefaultStandaloneDebug() const override { return true; }
diff --git a/test/CodeGen/dwarf-version.c b/test/CodeGen/dwarf-version.c
index 49c230d..cee0f03 100644
--- a/test/CodeGen/dwarf-version.c
+++ b/test/CodeGen/dwarf-version.c
@@ -4,7 +4,13 @@
 // RUN: %clang -target x86_64-linux-gnu -gdwarf-5 -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER5
 // RUN: %clang -target x86_64-linux-gnu -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER4
 // RUN: %clang -target x86_64-linux-gnu -gdwarf -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER4
-// RUN: %clang -target x86_64-apple-darwin -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER4
+
+// The -isysroot is used as a hack to avoid LIT messing with the SDKROOT
+// environment variable which indirecty overrides the version in the target
+// triple used here.
+// RUN: %clang -target x86_64-apple-macosx10.11 -g -S -emit-llvm -o - %s -isysroot %t | FileCheck %s --check-prefix=VER4
+// RUN: %clang -target x86_64-apple-darwin14 -g -S -emit-llvm -o - %s -isysroot %t | FileCheck %s --check-prefix=VER2
+
 // RUN: %clang -target powerpc-unknown-openbsd -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER2
 // RUN: %clang -target powerpc-unknown-freebsd -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER2
 // RUN: %clang -target i386-pc-solaris -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER2
diff --git a/test/Driver/clang-g-opts.c b/test/Driver/clang-g-opts.c
index 21b5cf6..a26fb29 100644
--- a/test/Driver/clang-g-opts.c
+++ b/test/Driver/clang-g-opts.c
@@ -4,7 +4,7 @@
 
 // Assert that the toolchains which should default to a lower Dwarf version do so.
 // RUN: %clang -### -S %s -g -target x86_64-apple-darwin 2>&1 \
-// RUN:             | FileCheck --check-prefix=CHECK-WITH-G-STANDALONE %s
+// RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
 // RUN: %clang -### -S %s -g -target i686-pc-openbsd 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
 // RUN: %clang -### -S %s -g -target x86_64-pc-freebsd10.0 2>&1 \
@@ -36,4 +36,4 @@
 // CHECK-WITH-G-DWARF2: "-dwarf-version=2"
 
 // CHECK-WITH-G-STANDALONE: "-debug-info-kind=standalone"
-// CHECK-WITH-G-STANDALONE: "-dwarf-version=4"
+// CHECK-WITH-G-STANDALONE: "-dwarf-version=2"
diff --git a/test/Driver/debug-options.c b/test/Driver/debug-options.c
index 0702811..94c769f 100644
--- a/test/Driver/debug-options.c
+++ b/test/Driver/debug-options.c
@@ -1,6 +1,7 @@
 // Check to make sure clang is somewhat picky about -g options.
 // rdar://10383444
 
+// Linux.
 // RUN: %clang -### -c -g %s -target x86_64-linux-gnu 2>&1 \
 // RUN:             | FileCheck -check-prefix=G -check-prefix=G_GDB %s
 // RUN: %clang -### -c -g2 %s -target x86_64-linux-gnu 2>&1 \
@@ -16,21 +17,50 @@
 // RUN: %clang -### -c -glldb %s -target x86_64-linux-gnu 2>&1 \
 // RUN:             | FileCheck -check-prefix=G -check-prefix=G_LLDB %s
 // RUN: %clang -### -c -gsce %s -target x86_64-linux-gnu 2>&1 \
+
+// Darwin.
 // RUN:             | FileCheck -check-prefix=G -check-prefix=G_SCE %s
-
 // RUN: %clang -### -c -g %s -target x86_64-apple-darwin 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_DARWIN -check-prefix=G_LLDB %s
-// RUN: %clang -### -c -g2 %s -target x86_64-apple-darwin 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_DARWIN %s
-// RUN: %clang -### -c -g3 %s -target x86_64-apple-darwin 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_DARWIN %s
-// RUN: %clang -### -c -ggdb %s -target x86_64-apple-darwin 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_DARWIN -check-prefix=G_GDB %s
-// RUN: %clang -### -c -ggdb1 %s -target x86_64-apple-darwin 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF2 \
+// RUN:                         -check-prefix=G_LLDB %s
+// RUN: %clang -### -c -g %s -target x86_64-apple-darwin16 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF4 \
+// RUN:                         -check-prefix=G_LLDB %s
+// RUN: %clang -### -c -g2 %s -target x86_64-apple-darwin16 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF4 %s
+// RUN: %clang -### -c -g3 %s -target x86_64-apple-darwin16 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF4 %s
+// RUN: %clang -### -c -ggdb %s -target x86_64-apple-darwin16 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF4 \
+// RUN:                         -check-prefix=G_GDB %s
+// RUN: %clang -### -c -ggdb1 %s -target x86_64-apple-darwin16 2>&1 \
 // RUN:             | FileCheck -check-prefix=GLTO_ONLY %s
-// RUN: %clang -### -c -ggdb3 %s -target x86_64-apple-darwin 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_DARWIN %s
+// RUN: %clang -### -c -ggdb3 %s -target x86_64-apple-darwin16 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF4 %s
+// RUN: %clang -### -c -g %s -target x86_64-apple-macosx10.11 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF4 %s
+// RUN: %clang -### -c -g %s -target x86_64-apple-macosx10.10 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_ONLY_DWARF2 %s
+// RUN: %clang -### -c -g %s -target armv7-apple-ios9.0 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF4 %s
+// RUN: %clang -### -c -g %s -target armv7-apple-ios8.0 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_ONLY_DWARF2 %s
+// RUN: %clang -### -c -g %s -target armv7k-apple-watchos 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF4 %s
+// RUN: %clang -### -c -g %s -target arm64-apple-tvos9.0 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE \
+// RUN:                         -check-prefix=G_DWARF4 %s
 
+// FreeBSD.
 // RUN: %clang -### -c -g %s -target x86_64-pc-freebsd10.0 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_GDB %s
 
@@ -47,7 +77,8 @@
 // RUN: %clang -### -c %s -g -gcolumn-info -target x86_64-scei-ps4 2>&1 \
 // RUN:             | FileCheck -check-prefix=CI %s
 
-// RUN: %clang -### -c -gdwarf-2 %s 2>&1 | FileCheck -check-prefix=G_D2 %s
+// RUN: %clang -### -c -gdwarf-2 %s 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_ONLY_DWARF2 %s
 //
 // RUN: %clang -### -c -gfoo %s 2>&1 | FileCheck -check-prefix=G_NO %s
 // RUN: %clang -### -c -g -g0 %s 2>&1 | FileCheck -check-prefix=G_NO %s
@@ -75,8 +106,8 @@
 // RUN:             | FileCheck -check-prefix=GLTO_ONLY_DWARF2 %s
 // RUN: %clang -### -c -gline-tables-only -g %s -target x86_64-linux-gnu 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_ONLY %s
-// RUN: %clang -### -c -gline-tables-only -g %s -target x86_64-apple-darwin 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_STANDALONE_DWARF4 %s
+// RUN: %clang -### -c -gline-tables-only -g %s -target x86_64-apple-darwin16 2>&1 \
+// RUN:             | FileCheck -check-prefix=G_STANDALONE -check-prefix=G_DWARF4 %s
 // RUN: %clang -### -c -gline-tables-only -g %s -target i686-pc-openbsd 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_ONLY_DWARF2 %s
 // RUN: %clang -### -c -gline-tables-only -g %s -target x86_64-pc-freebsd10.0 2>&1 \
@@ -121,9 +152,6 @@
 // G: "-cc1"
 // G: "-debug-info-kind=limited"
 //
-// G_DARWIN: "-cc1"
-// G_DARWIN: "-dwarf-version=4"
-//
 // NOG_PS4: "-cc1"
 // NOG_PS4-NOT "-dwarf-version=
 // NOG_PS4: "-generate-arange-section"
@@ -133,9 +161,6 @@
 // G_PS4: "-dwarf-version=
 // G_PS4: "-generate-arange-section"
 //
-// G_D2: "-cc1"
-// G_D2: "-dwarf-version=2"
-//
 // G_NO: "-cc1"
 // G_NO-NOT: -debug-info-kind=
 //
@@ -151,19 +176,19 @@
 // G_ONLY: "-cc1"
 // G_ONLY: "-debug-info-kind=limited"
 //
-// G_GDB:  "-debugger-tuning=gdb"
-// G_LLDB: "-debugger-tuning=lldb"
-// G_SCE:  "-debugger-tuning=sce"
-//
 // These tests assert that "-gline-tables-only" "-g" uses the latter,
 // but otherwise not caring about the DebugInfoKind.
 // G_ONLY_DWARF2: "-cc1"
 // G_ONLY_DWARF2: "-debug-info-kind={{standalone|limited}}"
 // G_ONLY_DWARF2: "-dwarf-version=2"
 //
-// G_STANDALONE_DWARF4: "-cc1"
-// G_STANDALONE_DWARF4: "-debug-info-kind=standalone"
-// G_STANDALONE_DWARF4: "-dwarf-version=4"
+// G_STANDALONE: "-cc1"
+// G_STANDALONE: "-debug-info-kind=standalone"
+// G_DWARF4: "-dwarf-version=4"
+//
+// G_GDB:  "-debugger-tuning=gdb"
+// G_LLDB: "-debugger-tuning=lldb"
+// G_SCE:  "-debugger-tuning=sce"
 //
 // This tests asserts that "-gline-tables-only" "-g0" disables debug info.
 // GLTO_NO: "-cc1"