Returned the option, but deprecated it

Author: DenisBakhvalov

clang/include/clang/Driver/Options.td

@@ -4370,6 +4370,10 @@ def fsycl : Flag<["-"], "fsycl">, Flags<[NoXarchOption, CoreOption]>, Group<sycl
   HelpText<"Enables SYCL kernels compilation for device">;
 def fno_sycl : Flag<["-"], "fno-sycl">, Flags<[NoXarchOption, CoreOption]>, Group<sycl_Group>,
   HelpText<"Disables SYCL kernels compilation for device">;
+defm sycl_esimd: BoolFOption<"sycl-explicit-simd",
+  LangOpts<"SYCLExplicitSIMD">, DefaultFalse,
+  PosFlag<SetTrue, [CC1Option], "Enable">, NegFlag<SetFalse, [], "Disable">,
+  BothFlags<[NoArgumentUnused, CoreOption], "SYCL explicit SIMD extension.">>;
 defm sycl_early_optimizations : OptOutFFlag<"sycl-early-optimizations", "Enable", "Disable", " standard optimization pipeline for SYCL device compiler", [CoreOption]>;
 def fsycl_dead_args_optimization : Flag<["-"], "fsycl-dead-args-optimization">,
   Group<sycl_Group>, Flags<[NoArgumentUnused, CoreOption]>, HelpText<"Enables "

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5406,7 +5406,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   }
 
   for (const Arg *A :
-       Args.filtered(options::OPT_clang_ignored_legacy_options_Group)) {
+       // TODO: remove -fsycl-explicit-simd when support is dropped.
+       Args.filtered(options::OPT_clang_ignored_legacy_options_Group,
+                     options::OPT_fsycl_esimd, options::OPT_fno_sycl_esimd)) {
     D.Diag(diag::warn_ignored_clang_option) << A->getAsString(Args);
     A->claim();
   }

clang/test/Driver/sycl-esimd.cpp

@@ -0,0 +1,4 @@
+/// Check that the warning is emmited for using "-fsycl-explicit-simd"
+// RUN: %clang -### -fsycl-explicit-simd %s 2>&1 | FileCheck %s
+// RUN: %clang -### -fno-sycl-explicit-simd %s 2>&1 | FileCheck %s
+// CHECK: the flag '-f{{.*}}sycl-explicit-simd' has been deprecated and will be ignored