Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -1804,6 +1804,21 @@
   if (!CPU.empty())
     CmdArgs.push_back(Args.MakeArgString(Twine("-plugin-opt=mcpu=") + CPU));
 
+  if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
+    if (A->getOption().matches(options::OPT_O4) ||
+        A->getOption().matches(options::OPT_Ofast)) {
+      CmdArgs.push_back("-plugin-opt=O3");
+    } else if (A->getOption().matches(options::OPT_O)) {
+      CmdArgs.push_back(
+          Args.MakeArgString(Twine("-plugin-opt=O") + A->getValue()));
+    } else if (A->getOption().matches(options::OPT_O0)) {
+      CmdArgs.push_back("-plugin-opt=O0");
+    } else {
+      ToolChain.getDriver().Diag(clang::diag::warn_drv_unused_argument)
+          << A->getAsString(Args);
+    }
+  }
+
   if (IsThinLTO)
     CmdArgs.push_back("-plugin-opt=thinlto");
 }
Index: test/Driver/gold-lto.c
===================================================================
--- test/Driver/gold-lto.c
+++ test/Driver/gold-lto.c
@@ -1,23 +1,26 @@
 // RUN: touch %t.o
 //
 // RUN: %clang -target x86_64-unknown-linux -### %t.o -flto 2>&1 \
-// RUN:     -Wl,-plugin-opt=foo \
+// RUN:     -Wl,-plugin-opt=foo -O3 \
 // RUN:     | FileCheck %s --check-prefix=CHECK-X86-64-BASIC
 // CHECK-X86-64-BASIC: "-plugin" "{{.*}}/LLVMgold.so"
+// CHECK-X86-64-BASIC: "-plugin-opt=O3"
 // CHECK-X86-64-BASIC: "-plugin-opt=foo"
 //
 // RUN: %clang -target x86_64-unknown-linux -### %t.o -flto 2>&1 \
-// RUN:     -march=corei7 -Wl,-plugin-opt=foo \
+// RUN:     -march=corei7 -Wl,-plugin-opt=foo -Ofast \
 // RUN:     | FileCheck %s --check-prefix=CHECK-X86-64-COREI7
 // CHECK-X86-64-COREI7: "-plugin" "{{.*}}/LLVMgold.so"
 // CHECK-X86-64-COREI7: "-plugin-opt=mcpu=corei7"
+// CHECK-X86-64-COREI7: "-plugin-opt=O3"
 // CHECK-X86-64-COREI7: "-plugin-opt=foo"
 //
 // RUN: %clang -target arm-unknown-linux -### %t.o -flto 2>&1 \
-// RUN:     -march=armv7a -Wl,-plugin-opt=foo \
+// RUN:     -march=armv7a -Wl,-plugin-opt=foo -O0 \
 // RUN:     | FileCheck %s --check-prefix=CHECK-ARM-V7A
 // CHECK-ARM-V7A: "-plugin" "{{.*}}/LLVMgold.so"
 // CHECK-ARM-V7A: "-plugin-opt=mcpu=cortex-a8"
+// CHECK-ARM-V7A: "-plugin-opt=O0"
 // CHECK-ARM-V7A: "-plugin-opt=foo"
 //
 // RUN: %clang -target i686-linux-android -### %t.o -flto 2>&1 \