Index: clang/include/clang/Basic/LangOptions.h
===================================================================
--- clang/include/clang/Basic/LangOptions.h
+++ clang/include/clang/Basic/LangOptions.h
@@ -130,6 +130,10 @@
   enum SYCLMajorVersion {
     SYCL_None,
     SYCL_2017,
+    SYCL_2020,
+    // The "default" SYCL version to be used when none is specified on the
+    // frontend command line.
+    SYCL_Default = SYCL_2020
   };
 
   /// Clang versions with different platform ABI conformance.
Index: clang/include/clang/Basic/LangOptions.def
===================================================================
--- clang/include/clang/Basic/LangOptions.def
+++ clang/include/clang/Basic/LangOptions.def
@@ -251,7 +251,7 @@
 
 LANGOPT(SYCLIsDevice      , 1, 0, "Generate code for SYCL device")
 LANGOPT(SYCLIsHost        , 1, 0, "SYCL host compilation")
-ENUM_LANGOPT(SYCLVersion  , SYCLMajorVersion, 1, SYCL_None, "Version of the SYCL standard used")
+ENUM_LANGOPT(SYCLVersion  , SYCLMajorVersion, 2, SYCL_None, "Version of the SYCL standard used")
 
 LANGOPT(HIPUseNewLaunchAPI, 1, 0, "Use new kernel launching API for HIP")
 
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -5671,8 +5671,8 @@
 def sycl_std_EQ : Joined<["-"], "sycl-std=">, Group<sycl_Group>,
   Flags<[CC1Option, NoArgumentUnused, CoreOption]>,
   HelpText<"SYCL language standard to compile for.">,
-  Values<"2017,121,1.2.1,sycl-1.2.1">,
-  NormalizedValues<["SYCL_2017", "SYCL_2017", "SYCL_2017", "SYCL_2017"]>,
+  Values<"2020,2017,121,1.2.1,sycl-1.2.1">,
+  NormalizedValues<["SYCL_2020", "SYCL_2017", "SYCL_2017", "SYCL_2017", "SYCL_2017"]>,
   NormalizedValuesScope<"LangOptions">,
   MarshallingInfoEnum<LangOpts<"SYCLVersion">, "SYCL_None">,
   ShouldParseIf<!strconcat(fsycl_is_device.KeyPath, "||", fsycl_is_host.KeyPath)>;
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -4284,8 +4284,8 @@
     if (Arg *A = Args.getLastArg(options::OPT_sycl_std_EQ)) {
       A->render(Args, CmdArgs);
     } else {
-      // Ensure the default version in SYCL mode is 1.2.1 (aka 2017)
-      CmdArgs.push_back("-sycl-std=2017");
+      // Ensure the default version in SYCL mode is 2020.
+      CmdArgs.push_back("-sycl-std=2020");
     }
   }
 
Index: clang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- clang/lib/Frontend/CompilerInvocation.cpp
+++ clang/lib/Frontend/CompilerInvocation.cpp
@@ -3635,6 +3635,16 @@
     }
   }
 
+  if ((Args.hasArg(OPT_fsycl_is_device) || Args.hasArg(OPT_fsycl_is_host)) &&
+      !Args.hasArg(OPT_sycl_std_EQ)) {
+    // If the user supplied -fsycl-is-device or -fsycl-is-host, but failed to
+    // provide -sycl-std=, we want to default it to whatever the default SYCL
+    // version is. I could not find a way to express this with the options
+    // tablegen because we still want this value to be SYCL_None when the user
+    // is not in device or host mode.
+    Opts.setSYCLVersion(LangOptions::SYCL_Default);
+  }
+
   if (Opts.ObjC) {
     if (Arg *arg = Args.getLastArg(OPT_fobjc_runtime_EQ)) {
       StringRef value = arg->getValue();
Index: clang/lib/Frontend/InitPreprocessor.cpp
===================================================================
--- clang/lib/Frontend/InitPreprocessor.cpp
+++ clang/lib/Frontend/InitPreprocessor.cpp
@@ -478,6 +478,8 @@
     // SYCL Version is set to a value when building SYCL applications
     if (LangOpts.getSYCLVersion() == LangOptions::SYCL_2017)
       Builder.defineMacro("CL_SYCL_LANGUAGE_VERSION", "121");
+    else if (LangOpts.getSYCLVersion() == LangOptions::SYCL_2020)
+      Builder.defineMacro("SYCL_LANGUAGE_VERSION", "202001");
   }
 
   // Not "standard" per se, but available even with the -undef flag.
Index: clang/test/Driver/sycl.c
===================================================================
--- clang/test/Driver/sycl.c
+++ clang/test/Driver/sycl.c
@@ -3,6 +3,7 @@
 // RUN: %clang -### -fsycl -sycl-std=1.2.1 %s 2>&1 | FileCheck %s --check-prefix=ENABLED
 // RUN: %clang -### -fsycl -sycl-std=121 %s 2>&1 | FileCheck %s --check-prefix=ENABLED
 // RUN: %clang -### -fsycl -sycl-std=2017 %s 2>&1 | FileCheck %s --check-prefix=ENABLED
+// RUN: %clang -### -fsycl -sycl-std=2020 %s 2>&1 | FileCheck %s --check-prefix=ENABLED
 // RUN: %clang -### -fsycl -sycl-std=sycl-1.2.1 %s 2>&1 | FileCheck %s --check-prefix=ENABLED
 // RUN: %clang -### -fno-sycl -fsycl %s 2>&1 | FileCheck %s --check-prefix=ENABLED
 // RUN: %clang -### -sycl-std=2017 %s 2>&1 | FileCheck %s --check-prefix=DISABLED
@@ -18,3 +19,9 @@
 // ENABLED-SAME: "-sycl-std={{[-.sycl0-9]+}}"
 // DISABLED-NOT: "-fsycl-is-device"
 // DISABLED-NOT: "-sycl-std="
+
+// RUN: %clang -### -fsycl  %s 2>&1 | FileCheck %s --check-prefix=DEFAULT
+// RUN: %clangxx -### -fsycl %s 2>&1 | FileCheck %s --check-prefix=DEFAULT
+// RUN: %clang_cl -### -fsycl %s 2>&1 | FileCheck %s --check-prefix=DEFAULT
+
+// DEFAULT: "-sycl-std=2020"
Index: clang/test/Preprocessor/sycl-macro.cpp
===================================================================
--- clang/test/Preprocessor/sycl-macro.cpp
+++ clang/test/Preprocessor/sycl-macro.cpp
@@ -1,10 +1,14 @@
 // RUN: %clang_cc1 %s -E -dM | FileCheck %s
 // RUN: %clang_cc1 %s -fsycl-is-device -sycl-std=2017 -E -dM | FileCheck --check-prefix=CHECK-SYCL-STD %s
 // RUN: %clang_cc1 %s -fsycl-is-host -sycl-std=2017 -E -dM | FileCheck --check-prefix=CHECK-SYCL-STD %s
+// RUN: %clang_cc1 %s -fsycl-is-host -sycl-std=2020 -E -dM | FileCheck --check-prefix=CHECK-SYCL-STD-2020 %s
+// RUN: %clang_cc1 %s -fsycl-is-host -E -dM | FileCheck --check-prefix=CHECK-SYCL-STD-2020 %s
 // RUN: %clang_cc1 %s -fsycl-is-device -sycl-std=1.2.1 -E -dM | FileCheck --check-prefix=CHECK-SYCL-STD %s
+// RUN: %clang_cc1 %s -fsycl-is-device -sycl-std=2020 -E -dM | FileCheck --check-prefix=CHECK-SYCL-STD-2020 %s
 // RUN: %clang_cc1 %s -fsycl-is-device -E -dM | FileCheck --check-prefixes=CHECK-SYCL %s
 
 // CHECK-NOT:#define __SYCL_DEVICE_ONLY__ 1
 // CHECK-NOT:#define CL_SYCL_LANGUAGE_VERSION 121
 // CHECK-SYCL-STD:#define CL_SYCL_LANGUAGE_VERSION 121
+// CHECK-SYCL-STD-2020:#define SYCL_LANGUAGE_VERSION 202001
 // CHECK-SYCL:#define __SYCL_DEVICE_ONLY__ 1
Index: clang/unittests/Frontend/CompilerInvocationTest.cpp
===================================================================
--- clang/unittests/Frontend/CompilerInvocationTest.cpp
+++ clang/unittests/Frontend/CompilerInvocationTest.cpp
@@ -566,18 +566,102 @@
   ASSERT_THAT(GeneratedArgs, Not(Contains(HasSubstr("-sycl-std="))));
 }
 
-TEST_F(CommandLineTest, ConditionalParsingIfTrueFlagNotPresent) {
+TEST_F(CommandLineTest, ConditionalParsingIfNonsenseSyclStdArg) {
+  const char *Args[] = {"-fsycl-is-device", "-sycl-std=garbage"};
+
+  CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags);
+
+  ASSERT_TRUE(Diags->hasErrorOccurred());
+  ASSERT_TRUE(Invocation.getLangOpts()->SYCLIsDevice);
+  ASSERT_FALSE(Invocation.getLangOpts()->SYCLIsHost);
+  ASSERT_EQ(Invocation.getLangOpts()->getSYCLVersion(), LangOptions::SYCL_None);
+
+  Invocation.generateCC1CommandLine(GeneratedArgs, *this);
+
+  ASSERT_THAT(GeneratedArgs, Contains(StrEq("-fsycl-is-device")));
+  ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq("-fsycl-is-host"))));
+  ASSERT_THAT(GeneratedArgs, Not(Contains(HasSubstr("-sycl-std="))));
+}
+
+TEST_F(CommandLineTest, ConditionalParsingIfOddSyclStdArg1) {
+  const char *Args[] = {"-fsycl-is-device", "-sycl-std=121"};
+
+  CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags);
+
+  ASSERT_FALSE(Diags->hasErrorOccurred());
+  ASSERT_TRUE(Invocation.getLangOpts()->SYCLIsDevice);
+  ASSERT_FALSE(Invocation.getLangOpts()->SYCLIsHost);
+  ASSERT_EQ(Invocation.getLangOpts()->getSYCLVersion(), LangOptions::SYCL_2017);
+
+  Invocation.generateCC1CommandLine(GeneratedArgs, *this);
+
+  ASSERT_THAT(GeneratedArgs, Contains(StrEq("-fsycl-is-device")));
+  ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq("-fsycl-is-host"))));
+  ASSERT_THAT(GeneratedArgs, Contains(HasSubstr("-sycl-std=2017")));
+}
+
+TEST_F(CommandLineTest, ConditionalParsingIfOddSyclStdArg2) {
+  const char *Args[] = {"-fsycl-is-device", "-sycl-std=1.2.1"};
+
+  CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags);
+
+  ASSERT_FALSE(Diags->hasErrorOccurred());
+  ASSERT_TRUE(Invocation.getLangOpts()->SYCLIsDevice);
+  ASSERT_FALSE(Invocation.getLangOpts()->SYCLIsHost);
+  ASSERT_EQ(Invocation.getLangOpts()->getSYCLVersion(), LangOptions::SYCL_2017);
+
+  Invocation.generateCC1CommandLine(GeneratedArgs, *this);
+
+  ASSERT_THAT(GeneratedArgs, Contains(StrEq("-fsycl-is-device")));
+  ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq("-fsycl-is-host"))));
+  ASSERT_THAT(GeneratedArgs, Contains(HasSubstr("-sycl-std=2017")));
+}
+
+TEST_F(CommandLineTest, ConditionalParsingIfOddSyclStdArg3) {
+  const char *Args[] = {"-fsycl-is-device", "-sycl-std=sycl-1.2.1"};
+
+  CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags);
+
+  ASSERT_FALSE(Diags->hasErrorOccurred());
+  ASSERT_TRUE(Invocation.getLangOpts()->SYCLIsDevice);
+  ASSERT_FALSE(Invocation.getLangOpts()->SYCLIsHost);
+  ASSERT_EQ(Invocation.getLangOpts()->getSYCLVersion(), LangOptions::SYCL_2017);
+
+  Invocation.generateCC1CommandLine(GeneratedArgs, *this);
+
+  ASSERT_THAT(GeneratedArgs, Contains(StrEq("-fsycl-is-device")));
+  ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq("-fsycl-is-host"))));
+  ASSERT_THAT(GeneratedArgs, Contains(HasSubstr("-sycl-std=2017")));
+}
+
+TEST_F(CommandLineTest, ConditionalParsingIfTrueFlagNotPresentHost) {
   const char *Args[] = {"-fsycl-is-host"};
 
   CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags);
 
   ASSERT_FALSE(Diags->hasErrorOccurred());
-  ASSERT_EQ(Invocation.getLangOpts()->getSYCLVersion(), LangOptions::SYCL_None);
+  ASSERT_EQ(Invocation.getLangOpts()->getSYCLVersion(),
+            LangOptions::SYCL_Default);
 
   Invocation.generateCC1CommandLine(GeneratedArgs, *this);
 
   ASSERT_THAT(GeneratedArgs, Contains(StrEq("-fsycl-is-host")));
-  ASSERT_THAT(GeneratedArgs, Not(Contains(HasSubstr("-sycl-std="))));
+  ASSERT_THAT(GeneratedArgs, Contains(HasSubstr("-sycl-std=")));
+}
+
+TEST_F(CommandLineTest, ConditionalParsingIfTrueFlagNotPresentDevice) {
+  const char *Args[] = {"-fsycl-is-device"};
+
+  CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags);
+
+  ASSERT_FALSE(Diags->hasErrorOccurred());
+  ASSERT_EQ(Invocation.getLangOpts()->getSYCLVersion(),
+            LangOptions::SYCL_Default);
+
+  Invocation.generateCC1CommandLine(GeneratedArgs, *this);
+
+  ASSERT_THAT(GeneratedArgs, Contains(StrEq("-fsycl-is-device")));
+  ASSERT_THAT(GeneratedArgs, Contains(HasSubstr("-sycl-std=")));
 }
 
 TEST_F(CommandLineTest, ConditionalParsingIfTrueFlagPresent) {