clang: Promote -fdebug-compilation-dir from cc1 flag to driver-level flag

[thakis]

Summary

The flag is useful when wanting to create .o files that are independent
from the absolute path to the build directory. -fdebug-prefix-map= can
be used to the same effect, but it requires putting the absolute path
to the build directory on the build command line, so it still requires
the build command line to be dependent on the absolute path of the build
directory. With this flag, "-fdebug-compilation-dir ." makes it so that
both debug info and the compile command itself are independent of the
absolute path of the build directory, which is good for build
determinism (in the sense that the build is independent of which
directory it happens in) and for caching compile results.

[hans]

lgtm

clang/include/clang/Driver/Options.td

717

Maybe mention in the commit message that it's not just a driver-level option, but also available in clang-cl (which makes sense I think).

clang/include/clang/Driver/CC1Options.td

 let Flags = [CC1Option, CC1AsOption, NoDriverOption] in {
 def debug_info_kind_EQ : Joined<["-"], "debug-info-kind=">;
 def debug_info_macro : Flag<["-"], "debug-info-macro">,
   HelpText<"Emit macro debug information">;
 def default_function_attr : Separate<["-"], "default-function-attr">,
   HelpText<"Apply given attribute to all functions">;
 def dwarf_version_EQ : Joined<["-"], "dwarf-version=">;
 def debugger_tuning_EQ : Joined<["-"], "debugger-tuning=">;
-def fdebug_compilation_dir : Separate<["-"], "fdebug-compilation-dir">,
-  HelpText<"The compilation directory to embed in the debug info.">;
 def dwarf_debug_flags : Separate<["-"], "dwarf-debug-flags">,
   HelpText<"The string to embed in the Dwarf debug flags record.">;
 def record_command_line : Separate<["-"], "record-command-line">,
   HelpText<"The string to embed in the .LLVM.command.line section.">;
 def compress_debug_sections : Flag<["-", "--"], "compress-debug-sections">,
     HelpText<"DWARF debug sections compression">;
 def compress_debug_sections_EQ : Joined<["-", "--"], "compress-debug-sections=">,
     HelpText<"DWARF debug sections compression type">;

clang/include/clang/Driver/Options.td

 def fno_auto_profile : Flag<["-"], "fno-auto-profile">, Group<f_Group>,
     Alias<fno_profile_sample_use>;
 def fauto_profile_EQ : Joined<["-"], "fauto-profile=">,
     Alias<fprofile_sample_use_EQ>;
 def fauto_profile_accurate : Flag<["-"], "fauto-profile-accurate">,
     Group<f_Group>, Alias<fprofile_sample_accurate>;
 def fno_auto_profile_accurate : Flag<["-"], "fno-auto-profile-accurate">,
     Group<f_Group>, Alias<fno_profile_sample_accurate>;
-def fdebug_info_for_profiling : Flag<["-"], "fdebug-info-for-profiling">, Group<f_Group>,
-    Flags<[CC1Option]>,
+def fdebug_compilation_dir : Separate<["-"], "fdebug-compilation-dir">,
+    Group<f_Group>, Flags<[CC1Option, CC1AsOption, CoreOption]>,
+    HelpText<"The compilation directory to embed in the debug info.">;
+def fdebug_info_for_profiling : Flag<["-"], "fdebug-info-for-profiling">,
+    Group<f_Group>, Flags<[CC1Option]>,
     HelpText<"Emit extra debug info to make sample profile more accurate.">;
-def fno_debug_info_for_profiling : Flag<["-"], "fno-debug-info-for-profiling">, Group<f_Group>,
-    Flags<[DriverOption]>,
+def fno_debug_info_for_profiling : Flag<["-"], "fno-debug-info-for-profiling">,
+    Group<f_Group>, Flags<[DriverOption]>,
     HelpText<"Do not emit extra debug info for sample profiler.">;
 def fprofile_instr_generate : Flag<["-"], "fprofile-instr-generate">,
     Group<f_Group>, Flags<[CoreOption]>,
     HelpText<"Generate instrumented code to collect execution counts into default.profraw file (overridden by '=' form of option or LLVM_PROFILE_FILE env var)">;
 def fprofile_instr_generate_EQ : Joined<["-"], "fprofile-instr-generate=">,
     Group<f_Group>, Flags<[CoreOption]>, MetaVarName<"<file>">,
     HelpText<"Generate instrumented code to collect execution counts into <file> (overridden by LLVM_PROFILE_FILE env var)">;
 def fprofile_instr_use : Flag<["-"], "fprofile-instr-use">, Group<f_Group>,

clang/lib/Driver/ToolChains/Clang.cpp

if (Triple.isPS4CPU())
     return false;
 
   return useFramePointerForTargetByDefault(Args, Triple);
 }
 
 /// Add a CC1 option to specify the debug compilation directory.
 static void addDebugCompDirArg(const ArgList &Args, ArgStringList &CmdArgs,
                                const llvm::vfs::FileSystem &VFS) {
-  if (llvm::ErrorOr<std::string> CWD = VFS.getCurrentWorkingDirectory()) {
+  if (Arg *A = Args.getLastArg(options::OPT_fdebug_compilation_dir)) {
+    CmdArgs.push_back("-fdebug-compilation-dir");
+    CmdArgs.push_back(A->getValue());
+  } else if (llvm::ErrorOr<std::string> CWD =
+                 VFS.getCurrentWorkingDirectory()) {
     CmdArgs.push_back("-fdebug-compilation-dir");
     CmdArgs.push_back(Args.MakeArgString(*CWD));
   }
 }
 
 /// Add a CC1 and CC1AS option to specify the debug file path prefix map.
 static void addDebugPrefixMapArg(const Driver &D, const ArgList &Args, ArgStringList &CmdArgs) {
   for (const Arg *A : Args.filtered(options::OPT_fdebug_prefix_map_EQ)) {
     StringRef Map = A->getValue();
     if (Map.find('=') == StringRef::npos)
       D.Diag(diag::err_drv_invalid_argument_to_fdebug_prefix_map) << Map;
     else
       CmdArgs.push_back(Args.MakeArgString("-fdebug-prefix-map=" + Map));
     A->claim();
   }
 }
 
 /// Vectorize at all optimization levels greater than 1 except for -Oz.
-/// For -Oz the loop vectorizer is disable, while the slp vectorizer is enabled.
+/// For -Oz the loop vectorizer is disabled, while the slp vectorizer is
+/// enabled.
 static bool shouldEnableVectorizerAtOLevel(const ArgList &Args, bool isSlpVec) {
   if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
     if (A->getOption().matches(options::OPT_O4) ||
         A->getOption().matches(options::OPT_Ofast))
       return true;
 
     if (A->getOption().matches(options::OPT_O0))
       return false;

clang/test/Driver/cl-options.c

 // RUN:     -fno-builtin \
 // RUN:     -fno-builtin-strcpy \
 // RUN:     -fcolor-diagnostics \
 // RUN:     -fno-color-diagnostics \
 // RUN:     -fcoverage-mapping \
 // RUN:     -fno-coverage-mapping \
 // RUN:     -fdiagnostics-color \
 // RUN:     -fno-diagnostics-color \
+// RUN:     -fdebug-compilation-dir . \
 // RUN:     -fdiagnostics-parseable-fixits \
 // RUN:     -fdiagnostics-absolute-paths \
 // RUN:     -ferror-limit=10 \
 // RUN:     -fmsc-version=1800 \
 // RUN:     -fno-strict-aliasing \
 // RUN:     -fstrict-aliasing \
 // RUN:     -fsyntax-only \
 // RUN:     -fms-compatibility \

clang/test/Driver/clang_f_opts.c

 // RUN: %clang -### -S %s 2>&1 | FileCheck -check-prefix=CHECK-NO-CF-PROTECTION-RETURN %s
 // CHECK-CF-PROTECTION-RETURN: -fcf-protection=return
 // CHECK-NO-CF-PROTECTION-RETURN-NOT: -fcf-protection=return
 // RUN: %clang -### -S -fcf-protection=branch %s 2>&1 | FileCheck -check-prefix=CHECK-CF-PROTECTION-BRANCH %s
 // RUN: %clang -### -S %s 2>&1 | FileCheck -check-prefix=CHECK-NO-CF-PROTECTION-BRANCH %s
 // CHECK-CF-PROTECTION-BRANCH: -fcf-protection=branch
 // CHECK-NO-CF-PROTECTION-BRANCH-NOT: -fcf-protection=branch
 
+// RUN: %clang -### -S -fdebug-compilation-dir . %s 2>&1 | FileCheck -check-prefix=CHECK-DEBUG-COMPILATION-DIR %s
+// RUN: %clang -### -fdebug-compilation-dir . -x assembler %s 2>&1 | FileCheck -check-prefix=CHECK-DEBUG-COMPILATION-DIR %s
+// CHECK-DEBUG-COMPILATION-DIR: "-fdebug-compilation-dir" "."
+
 // RUN: %clang -### -S -fdiscard-value-names %s 2>&1 | FileCheck -check-prefix=CHECK-DISCARD-NAMES %s
 // RUN: %clang -### -S -fno-discard-value-names %s 2>&1 | FileCheck -check-prefix=CHECK-NO-DISCARD-NAMES %s
 // CHECK-DISCARD-NAMES: "-discard-value-names"
 // CHECK-NO-DISCARD-NAMES-NOT: "-discard-value-names"
-//
+
 // RUN: %clang -### -S -fmerge-all-constants %s 2>&1 | FileCheck -check-prefix=CHECK-MERGE-ALL-CONSTANTS %s
 // RUN: %clang -### -S -fno-merge-all-constants %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MERGE-ALL-CONSTANTS %s
 // RUN: %clang -### -S -fmerge-all-constants -fno-merge-all-constants %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MERGE-ALL-CONSTANTS %s
 // RUN: %clang -### -S -fno-merge-all-constants -fmerge-all-constants %s 2>&1 | FileCheck -check-prefix=CHECK-MERGE-ALL-CONSTANTS %s
 // CHECK-NO-MERGE-ALL-CONSTANTS-NOT: "-fmerge-all-constants"
 // CHECK-MERGE-ALL-CONSTANTS: "-fmerge-all-constants"
 
 // RUN: %clang -### -S -fdelete-null-pointer-checks %s 2>&1 | FileCheck -check-prefix=CHECK-NULL-POINTER-CHECKS %s