diff --git a/clang/test/Driver/darwin-sdkroot.c b/clang/test/Driver/darwin-sdkroot.c
index 8b3782ea22a7..700993fa96a6 100644
--- a/clang/test/Driver/darwin-sdkroot.c
+++ b/clang/test/Driver/darwin-sdkroot.c
@@ -2,7 +2,7 @@
 //
 // RUN: rm -rf %t.tmpdir
 // RUN: mkdir -p %t.tmpdir
-// RUN: env SDKROOT=%t.tmpdir %clang -target x86_64-apple-darwin10 \
+// RUN: env SDKROOT=%t.tmpdir %clang -target x86_64-apple-darwin10 --sysroot="" \
 // RUN:   -c %s -### 2> %t.log
 // RUN: FileCheck --check-prefix=CHECK-BASIC < %t.log %s
 //
@@ -13,7 +13,7 @@
 // Check that we don't use SDKROOT as the default if it is not a valid path.
 //
 // RUN: rm -rf %t.nonpath
-// RUN: env SDKROOT=%t.nonpath %clang -target x86_64-apple-darwin10 \
+// RUN: env SDKROOT=%t.nonpath %clang -target x86_64-apple-darwin10 --sysroot="" \
 // RUN:   -c %s -### 2> %t.log
 // RUN: FileCheck --check-prefix=CHECK-NONPATH < %t.log %s
 //
@@ -23,7 +23,7 @@
 
 // Check that we don't use SDKROOT as the default if it is just "/"
 //
-// RUN: env SDKROOT=/ %clang -target x86_64-apple-darwin10 \
+// RUN: env SDKROOT=/ %clang -target x86_64-apple-darwin10 --sysroot="" \
 // RUN:   -c %s -### 2> %t.log
 // RUN: FileCheck --check-prefix=CHECK-NONROOT < %t.log %s
 //
@@ -43,7 +43,7 @@
 //
 // RUN: rm -rf %t/SDKs/iPhoneOS8.0.0.sdk
 // RUN: mkdir -p %t/SDKs/iPhoneOS8.0.0.sdk
-// RUN: env SDKROOT=%t/SDKs/iPhoneOS8.0.0.sdk %clang -target arm64-apple-darwin %s -### 2>&1 \
+// RUN: env SDKROOT=%t/SDKs/iPhoneOS8.0.0.sdk %clang -target arm64-apple-darwin --sysroot="" %s -### 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-IPHONE %s
 //
 // CHECK-IPHONE: clang
@@ -55,7 +55,7 @@
 //
 // RUN: rm -rf %t/SDKs/iPhoneSimulator8.0.sdk
 // RUN: mkdir -p %t/SDKs/iPhoneSimulator8.0.sdk
-// RUN: env SDKROOT=%t/SDKs/iPhoneSimulator8.0.sdk %clang -target x86_64-apple-darwin %s -### 2>&1 \
+// RUN: env SDKROOT=%t/SDKs/iPhoneSimulator8.0.sdk %clang -target x86_64-apple-darwin --sysroot="" %s -### 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-SIMULATOR %s
 //
 // CHECK-SIMULATOR: clang
@@ -66,7 +66,7 @@
 //
 // RUN: rm -rf %t/SDKs/MacOSX10.10.0.sdk
 // RUN: mkdir -p %t/SDKs/MacOSX10.10.0.sdk
-// RUN: env SDKROOT=%t/SDKs/MacOSX10.10.0.sdk %clang -target x86_64-apple-darwin %s -### 2>&1 \
+// RUN: env SDKROOT=%t/SDKs/MacOSX10.10.0.sdk %clang -target x86_64-apple-darwin --sysroot="" %s -### 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MACOSX %s
 //
 // CHECK-MACOSX: clang
diff --git a/clang/test/Driver/gcc-toolchain.cpp b/clang/test/Driver/gcc-toolchain.cpp
index ca96757a2bbc..6c872f4255c3 100644
--- a/clang/test/Driver/gcc-toolchain.cpp
+++ b/clang/test/Driver/gcc-toolchain.cpp
@@ -3,12 +3,14 @@
 // RUN: %clangxx -no-canonical-prefixes %s -### -o %t 2>&1 \
 // RUN:     --target=i386-unknown-linux -stdlib=libstdc++ \
 // RUN:     --gcc-toolchain=%S/Inputs/ubuntu_11.04_multiarch_tree/usr \
+// RUN:     --sysroot="" \
 // RUN:   | FileCheck %s
 //
 // Additionally check that the legacy spelling of the flag works.
 // RUN: %clangxx -no-canonical-prefixes %s -### -o %t 2>&1 \
 // RUN:     --target=i386-unknown-linux -stdlib=libstdc++ \
 // RUN:     -gcc-toolchain %S/Inputs/ubuntu_11.04_multiarch_tree/usr \
+// RUN:     --sysroot="" \
 // RUN:   | FileCheck %s
 //
 // Test for header search toolchain detection.
diff --git a/clang/test/Driver/mips-mti.cpp b/clang/test/Driver/mips-mti.cpp
index 147239cf3759..94c3c5568e33 100644
--- a/clang/test/Driver/mips-mti.cpp
+++ b/clang/test/Driver/mips-mti.cpp
@@ -4,6 +4,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EB -mhard-float -mabi=32 \
 // RUN:   | FileCheck --check-prefix=EB-HARD-O32 %s
@@ -32,6 +33,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EB -mhard-float -mabi=n32 \
 // RUN:   | FileCheck --check-prefix=EB-HARD-N32 %s
@@ -60,6 +62,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips64-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EB -mhard-float -mabi=64 \
 // RUN:   | FileCheck --check-prefix=EB-HARD-N64 %s
@@ -88,6 +91,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EL -mhard-float -mabi=32 \
 // RUN:   | FileCheck --check-prefix=EL-HARD-O32 %s
@@ -116,6 +120,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EL -mhard-float -mabi=n32 \
 // RUN:   | FileCheck --check-prefix=EL-HARD-N32 %s
@@ -144,6 +149,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips64-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EL -mhard-float -mabi=64 \
 // RUN:   | FileCheck --check-prefix=EL-HARD-N64 %s
@@ -172,6 +178,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EB -msoft-float \
 // RUN:   | FileCheck --check-prefix=EB-SOFT %s
@@ -200,6 +207,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EL -msoft-float \
 // RUN:   | FileCheck --check-prefix=EL-SOFT %s
@@ -228,6 +236,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EB -mhard-float -muclibc \
 // RUN:   | FileCheck --check-prefix=EB-HARD-UCLIBC %s
@@ -256,6 +265,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EL -mhard-float -muclibc \
 // RUN:   | FileCheck --check-prefix=EL-HARD-UCLIBC %s
@@ -284,6 +294,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EB -mhard-float -mnan=2008 \
 // RUN:   | FileCheck --check-prefix=EB-HARD-NAN2008 %s
@@ -312,6 +323,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EL -mhard-float -mnan=2008 \
 // RUN:   | FileCheck --check-prefix=EL-HARD-NAN2008 %s
@@ -340,6 +352,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EB -mhard-float -muclibc -mnan=2008 \
 // RUN:   | FileCheck --check-prefix=EB-HARD-UCLIBC-NAN2008 %s
@@ -368,6 +381,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EL -mhard-float -muclibc -mnan=2008 \
 // RUN:   | FileCheck --check-prefix=EL-HARD-UCLIBC-NAN2008 %s
@@ -396,6 +410,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EL -msoft-float -mmicromips \
 // RUN:   | FileCheck --check-prefix=EL-SOFT-MICRO %s
@@ -424,6 +439,7 @@
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:        --target=mips-mti-linux-gnu \
 // RUN:        --gcc-toolchain=%S/Inputs/mips_mti_tree \
+// RUN:        --sysroot="" \
 // RUN:        -stdlib=libstdc++ \
 // RUN:        -EL -mhard-float -mmicromips -mnan=2008 \
 // RUN:   | FileCheck --check-prefix=EL-SOFT-MICRO-NAN2008 %s
diff --git a/clang/test/Driver/msp430-toolchain.c b/clang/test/Driver/msp430-toolchain.c
index 62ef1c0c1f15..f741491c94e8 100644
--- a/clang/test/Driver/msp430-toolchain.c
+++ b/clang/test/Driver/msp430-toolchain.c
@@ -1,11 +1,11 @@
 // A basic clang -cc1 command-line, and simple environment check.
 
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=CC1 %s
 // CC1: clang{{.*}} "-cc1" "-triple" "msp430"
 
 // RUN: %clang %s -### -no-canonical-prefixes -target msp430 \
-// RUN:   --gcc-toolchain=%S/Inputs/basic_msp430_tree 2>&1 \
+// RUN:   --gcc-toolchain=%S/Inputs/basic_msp430_tree --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430 %s
 
 // MSP430: "{{.*}}Inputs/basic_msp430_tree/lib/gcc/msp430-elf/7.3.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}msp430-elf-ld"
@@ -18,7 +18,7 @@
 // MSP430: "{{.*}}/Inputs/basic_msp430_tree/lib/gcc/msp430-elf/7.3.1/../../..{{/|\\\\}}..{{/|\\\\}}msp430-elf{{/|\\\\}}lib/430{{/|\\\\}}crtn.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -target msp430 -nodefaultlibs \
-// RUN:   --gcc-toolchain=%S/Inputs/basic_msp430_tree 2>&1 \
+// RUN:   --gcc-toolchain=%S/Inputs/basic_msp430_tree --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-NO-DFT-LIB %s
 
 // MSP430-NO-DFT-LIB: "{{.*}}Inputs/basic_msp430_tree/lib/gcc/msp430-elf/7.3.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}msp430-elf-ld"
@@ -31,7 +31,7 @@
 // MSP430-NO-DFT-LIB: "{{.*}}/Inputs/basic_msp430_tree/lib/gcc/msp430-elf/7.3.1/../../..{{/|\\\\}}..{{/|\\\\}}msp430-elf{{/|\\\\}}lib/430{{/|\\\\}}crtn.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -target msp430 -nostartfiles \
-// RUN:   --gcc-toolchain=%S/Inputs/basic_msp430_tree 2>&1 \
+// RUN:   --gcc-toolchain=%S/Inputs/basic_msp430_tree --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-NO-START %s
 
 // MSP430-NO-START: "{{.*}}Inputs/basic_msp430_tree/lib/gcc/msp430-elf/7.3.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}msp430-elf-ld"
@@ -40,7 +40,7 @@
 // MSP430-NO-START: "--start-group" "-lmul_none" "-lgcc" "-lc" "-lcrt" "-lnosys" "--end-group"
 
 // RUN: %clang %s -### -no-canonical-prefixes -target msp430 -nostdlib \
-// RUN:   --gcc-toolchain=%S/Inputs/basic_msp430_tree 2>&1 \
+// RUN:   --gcc-toolchain=%S/Inputs/basic_msp430_tree --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-NO-STD-LIB %s
 
 // MSP430-NO-STD-LIB: "{{.*}}Inputs/basic_msp430_tree/lib/gcc/msp430-elf/7.3.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}msp430-elf-ld"
@@ -48,31 +48,31 @@
 // MSP430-NO-STD-LIB: "-L{{.*}}/Inputs/basic_msp430_tree/lib/gcc/msp430-elf/7.3.1/../../..{{/|\\\\}}..{{/|\\\\}}msp430-elf{{/|\\\\}}lib/430"
 // MSP430-NO-STD-LIB: "--start-group" "-lmul_none" "-lgcc" "--end-group"
 
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mmcu=msp430f147 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mmcu=msp430f147 --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-HWMult-16BIT %s
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mmcu=msp430f147 -mhwmult=auto 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mmcu=msp430f147 -mhwmult=auto --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-HWMult-16BIT %s
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=16bit 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=16bit --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-HWMult-16BIT %s
 
 // MSP430-HWMult-16BIT: "--start-group" "-lmul_16"
 
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mmcu=msp430f4783 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mmcu=msp430f4783 --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-HWMult-32BIT %s
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mmcu=msp430f4783 -mhwmult=auto 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mmcu=msp430f4783 -mhwmult=auto --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-HWMult-32BIT %s
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=32bit 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=32bit --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-HWMult-32BIT %s
 
 // MSP430-HWMult-32BIT: "--start-group" "-lmul_32"
 
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=f5series 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=f5series --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-HWMult-F5 %s
 // MSP430-HWMult-F5: "--start-group" "-lmul_f5"
 
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=none 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=none --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-HWMult-NONE %s
-// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=none -mmcu=msp430f4783 2>&1 \
+// RUN: %clang %s -### -no-canonical-prefixes -target msp430 -mhwmult=none -mmcu=msp430f4783 --sysroot="" 2>&1 \
 // RUN:   | FileCheck -check-prefix=MSP430-HWMult-NONE %s
 
 // MSP430-HWMult-NONE: "--start-group" "-lmul_none"
diff --git a/clang/unittests/Driver/ToolChainTest.cpp b/clang/unittests/Driver/ToolChainTest.cpp
index 80938c83f824..f84e508b6cbd 100644
--- a/clang/unittests/Driver/ToolChainTest.cpp
+++ b/clang/unittests/Driver/ToolChainTest.cpp
@@ -60,7 +60,7 @@ TEST(ToolChainTest, VFSGCCInstallation) {
                                 llvm::MemoryBuffer::getMemBuffer("\n"));
 
   std::unique_ptr<Compilation> C(TheDriver.BuildCompilation(
-      {"-fsyntax-only", "--gcc-toolchain=", "foo.cpp"}));
+      {"-fsyntax-only", "--gcc-toolchain=", "--sysroot=", "foo.cpp"}));
   EXPECT_TRUE(C);
 
   std::string S;