[NFC] Update documentation for -fsycl-instrument-device-code (#6229)

Add additional details to the help and the UserManual for the
-fsycl-instrument-device-code option.

Author: mdtoguchi

clang/include/clang/Driver/Options.td

@@ -2770,10 +2770,14 @@ def fsycl_device_code_split_EQ : Joined<["-"], "fsycl-device-code-split=">,
 def fsycl_device_code_split : Flag<["-"], "fsycl-device-code-split">, Alias<fsycl_device_code_split_EQ>,
   AliasArgs<["auto"]>, Flags<[CC1Option, CoreOption]>,
   HelpText<"Perform SYCL device code split in the 'auto' mode, i.e. use heuristic to distribute device code across modules">;
-defm sycl_instrument_device_code : BoolFOption<"sycl-instrument-device-code",
-  CodeGenOpts<"SPIRITTAnnotations">, DefaultFalse,
-  PosFlag<SetTrue, [], "Add">, NegFlag<SetFalse, [], "Do not add">,
-  BothFlags<[CC1Option, CoreOption], " ITT instrumentation intrinsics calls">>;
+defm sycl_instrument_device_code
+    : BoolFOption<"sycl-instrument-device-code",
+          CodeGenOpts<"SPIRITTAnnotations">, DefaultFalse,
+          PosFlag<SetTrue, [], "Add">,
+          NegFlag<SetFalse, [], "Do not add">,
+          BothFlags<[CC1Option, CoreOption], " Instrumentation and Tracing "
+                    "Technology (ITT) instrumentation intrinsics calls "
+                    "(experimental)">>;
 defm sycl_id_queries_fit_in_int: BoolFOption<"sycl-id-queries-fit-in-int",
   LangOpts<"SYCLValueFitInMaxInt">, DefaultTrue,
   PosFlag<SetTrue, [], "Assume">, NegFlag<SetFalse, [], "Do not assume">,

sycl/doc/UsersManual.md

@@ -199,6 +199,13 @@ and not recommended to use in production environment.
     otherwise the link will happen in build time, online link is disabled by
     default currently. This option is ignored in AOT compilation.
 
+**`-f[no-]sycl-instrument-device-code`** [EXPERIMENTAL]
+
+    Enables/disables linking of the Instrumentation and Tracing Technology (ITT)
+    device libraries for VTune(R). This provides annotations to intercept
+    various events inside JIT generated kernels. These device libraries are
+    linked in by default.
+
 ## Intel FPGA specific options
 
 **`-fintelfpga`**