[Driver] Make "-fno-split-machine-functions" a valid flag for all archs

[shenhan]

Summary

Previously, when clang reports an error when -fno-split-machine-functions is used for non-X86 archs.

However, in some cases, users may specify flags as "-fsplit-machine-functions -fother-flags -fno-split-machine-functions", the first one is from a global flag set, the last one is used to negate the global flag, we think this is a valid usage mode.

Another cases is when clang is used to invoke multiple workloads, like "-x cuda -fsplit-machine-functions -Xarch_device -fno-split-machine-functions", the latter is used to negate the global -fsplit-machine-functions when invoke workloads for GPU."

This change makes this work, so all below are valid usages and does not have any warnings:

• ./bin/clang -x cuda -nocudalib -nocudainc -Xarch_host -fsplit-machine-functions -S ~/test.c
• ./bin/clang -x cuda -nocudalib -nocudainc -fsplit-machine-functions -Xarch_device -fnosplit-machine-functions -S ~/test.c
• ./bin/clang -x cuda -nocudalib -nocudainc -Xarch_host -fsplit-machine-functions -Xarch_device -fnosplit-machine-functions -S ~/test.c

[MaskRay]

Thanks for the patch. We need a test. I cleaned up fsplit-machine-functions.c a bit. You can rebase and modify the not %clang -### -c --target=arm-unknown-linux -fsplit-machine-functions -fno-split-machine-functions RUN line in clang/test/Driver/fsplit-machine-function.c

[shenhan]

In D158755#4614566, @MaskRay wrote:

Thanks for the patch. We need a test. I cleaned up fsplit-machine-functions.c a bit. You can rebase and modify the not %clang -### -c --target=arm-unknown-linux -fsplit-machine-functions -fno-split-machine-functions RUN line in clang/test/Driver/fsplit-machine-function.c

Thanks. Fixed the case tagged with "FIXME" and added some new cases.

[MaskRay]

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

19

We should not test clang: before error:. It may be a different string in certain builds where %clang is a symlink to a file not named clang. This would also fail on Windows. Rule of thumb: don't test the exact string before error:

21

We don't really need new tests. The existing --target=arm-unknown-linux one I added is sufficient.

[shenhan]

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

19

Acked.

21

Done, removed newly added cases.

[MaskRay]

With a test nit

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

19

Suggest that we add -Werror (%clang -### -Werror ...) to additionally test that there is no warning. -Werror upgrades warnings to errors, which would cause -### to exit with 1. This is a recent change of mine to make -### stricter.

[MaskRay]

Make "-fno-split-machine-functions" a valid flag for all archs.

Driver changes usually are named [Driver] .... The popular convention is to omit the full stop at the end of the subject.

clang/lib/Driver/ToolChains/Clang.cpp

Args.addOptInFlag(CmdArgs, options::OPT_funique_internal_linkage_names,
                     options::OPT_fno_unique_internal_linkage_names);
   Args.addOptInFlag(CmdArgs, options::OPT_funique_basic_block_section_names,
                     options::OPT_fno_unique_basic_block_section_names);
   Args.addOptInFlag(CmdArgs, options::OPT_fconvergent_functions,
                     options::OPT_fno_convergent_functions);
 
   if (Arg *A = Args.getLastArg(options::OPT_fsplit_machine_functions,
                                options::OPT_fno_split_machine_functions)) {
+    if (!A->getOption().matches(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 (Triple.isX86() && Triple.isOSBinFormatELF())
         A->render(Args, CmdArgs);
-    } else {
+      else
         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);
 
   // NVPTX/AMDGCN doesn't support PGO or coverage. There's no runtime support

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

 // RUN: %clang -### --target=x86_64-linux -flto -fsplit-machine-functions -fno-split-machine-functions %s 2>&1 | FileCheck %s --check-prefix=LTO-NEG
 
 // LTO:         "-plugin-opt=-split-machine-functions"
 // LTO-NEG-NOT: "-plugin-opt=-split-machine-functions"
 
 // RUN: not %clang -### -c --target=arm-unknown-linux -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefix=ERR
 // ERR: error: unsupported option '-fsplit-machine-functions' for target
 
-/// FIXME
-// RUN: not %clang -### -c --target=arm-unknown-linux -fsplit-machine-functions -fno-split-machine-functions %s 2>&1 | FileCheck %s --check-prefix=ERR2
-// ERR2: error: unsupported option '-fno-split-machine-functions' for target
+// RUN: %clang -### --target=arm-unknown-linux -fsplit-machine-functions -fno-split-machine-functions %s