[clang] Remove profile available check for fsplit-machine-functions.

[snehasish]

Summary

Enforcing a profile available check in the driver does not work with
incremental LTO builds where the LTO backend invocation does not include
the profile flags. At this point the profiles have already been consumed
and the IR contains profile metadata. Instead we always pass through the
-fsplit-machine-functions flag on user request. The pass itself contains
a check to return early if no profile information is available.

[tejohnson]

lgtm with a couple of minor suggestions

clang/lib/Driver/ToolChains/Clang.cpp

4918–4919

nit, remove braces per coding convention.

clang/test/Driver/fsplit-machine-functions.c

3

Might want to check that we get the option despite not having fprofile-use

[snehasish]

Drop braces, add a test.

• Remove braces from single line if.
• Add a test to make sure that option is passed through even if no profiles provided.

[snehasish]

Thanks for the quick review!

clang/lib/Driver/ToolChains/Clang.cpp

#endif
 
   if (Args.hasFlag(options::OPT_funique_basic_block_section_names,
                    options::OPT_fno_unique_basic_block_section_names, false))
     CmdArgs.push_back("-funique-basic-block-section-names");
 
   if (Arg *A = Args.getLastArg(options::OPT_fsplit_machine_functions,
                                options::OPT_fno_split_machine_functions)) {
     // This codegen pass is only available on x86-elf targets.
     if (Triple.isX86() && Triple.isOSBinFormatELF()) {
-      if (A->getOption().matches(options::OPT_fsplit_machine_functions)) {
-        // If the flag is enabled but no profile information is available then
-        // emit a warning.
-        if (getLastProfileUseArg(Args) || getLastProfileSampleUseArg(Args)) {
-          A->render(Args, CmdArgs);
-        } else {
-          D.Diag(diag::warn_drv_diagnostics_hotness_requires_pgo)
-              << A->getAsString(Args);
-        }
-      }
-    } else {
+      if (A->getOption().matches(options::OPT_fsplit_machine_functions))
       D.Diag(diag::err_drv_unsupported_opt_for_target)
           << A->getAsString(Args) << TripleStr;
     }
   }
 
   Args.AddLastArg(CmdArgs, options::OPT_finstrument_functions,
                   options::OPT_finstrument_functions_after_inlining,
                   options::OPT_finstrument_function_entry_bare);

clang/test/Driver/fsplit-machine-functions.c

 // RUN: %clang -### -target x86_64 -fprofile-use=default.profdata -fsplit-machine-functions %s -c 2>&1 | FileCheck -check-prefix=CHECK-OPT %s
+// RUN: %clang -### -target x86_64 -fsplit-machine-functions %s -c 2>&1 | FileCheck -check-prefix=CHECK-OPT %s
 // RUN: %clang -### -target x86_64 -fprofile-use=default.profdata -fsplit-machine-functions -fno-split-machine-functions %s -c 2>&1 | FileCheck -check-prefix=CHECK-NOOPT %s
-// RUN: %clang -### -target x86_64 -fsplit-machine-functions %s 2>&1 | FileCheck -check-prefix=CHECK-WARN %s
 // RUN: not %clang -c -target arm-unknown-linux -fsplit-machine-functions %s 2>&1 | FileCheck -check-prefix=CHECK-TRIPLE %s
 
 // CHECK-OPT:       "-fsplit-machine-functions"
 // CHECK-NOOPT-NOT: "-fsplit-machine-functions"
-// CHECK-WARN:      warning: argument '-fsplit-machine-functions' requires profile-guided optimization information
 // CHECK-TRIPLE:    error: unsupported option '-fsplit-machine-functions' for target