[Driver] Let -fno-integrated-as -gdwarf-5 use -fdwarf-directory-asm

[MaskRay]

Summary

While GNU as only allows the directory form of the .file directive for DWARF v5,
the integrated assembler prefers the directory form on all DWARF versions
(-fdwarf-directory-asm).

We currently set CC1 -fno-dwarf-directory-asm for -fno-integrated-as -gdwarf-5
which may cause the directory entry 0 and the filename entry 0 to be incorrect
(see D105662 and the example below). This patch makes -fno-integrated-as -gdwarf-5 use
-fdwarf-directory-asm as well.

cd /tmp/c

before
% clang -g -gdwarf-5 -fno-integrated-as e/a.c -S -o - | grep '\.file.*0'
        .file   0 "/tmp/c/e/a.c" md5 0x97e31cee64b4e58a4af8787512d735b6
% clang -g -gdwarf-5 -fno-integrated-as e/a.c -c
% llvm-dwarfdump a.o | grep include_directories
include_directories[  0] = "/tmp/c/e"

after
% clang -g -gdwarf-5 -fno-integrated-as e/a.c -S -o - | grep '\.file.*0'
        .file   0 "/tmp/c" "e/a.c" md5 0x97e31cee64b4e58a4af8787512d735b6
% clang -g -gdwarf-5 -fno-integrated-as e/a.c -c
% llvm-dwarfdump a.o | grep include_directories
include_directories[  0] = "/tmp/c"

[dblaikie]

Not sure I quite follow - is this an alternative to/replacement for D105662? Is the intent to revert D105662 after this (D105835) (& some corresponding change to llc?) lands?

[MaskRay]

In D105835#2872362, @dblaikie wrote:

Not sure I quite follow - is this an alternative to/replacement for D105662? Is the intent to revert D105662 after this (D105835) (& some corresponding change to llc?) lands?

It is an alternative to D105662.

This fixes the root cause: UseDwarfDirectory should be true with -fno-integrated-as -gdwarf-5.

[osandov]

I tested my reproducer and it also fixes it, thanks. Should it be an error to specify -fno-dwarf-directory-asm together with -gdwarf-5, since that produces incorrect results?

[MaskRay]

In D105835#2872393, @osandov wrote:

I tested my reproducer and it also fixes it, thanks. Should it be an error to specify -fno-dwarf-directory-asm together with -gdwarf-5, since that produces incorrect results?

I thought about this, but did not add the code because I think the option -fno-dwarf-directory-asm is so obscure that probably nobody will use...
Not sure why it became a driver option... An internal CC1 option probably suffices.

[osandov]

That's fair enough. I don't know if I'm qualified to review this, but this I think this is a better solution than my fix.

[dblaikie]

Sure, sounds OK. Please make the corresponding change to llc and revert the other patch after this one & the llc one are done.

clang/lib/Driver/ToolChains/Clang.cpp

static bool ShouldEnableAutolink(const ArgList &Args, const ToolChain &TC,
   // The linker_option directives are intended for host compilation.
   if (JA.isDeviceOffloading(Action::OFK_Cuda) ||
       JA.isDeviceOffloading(Action::OFK_HIP))
     Default = false;
   return Args.hasFlag(options::OPT_fautolink, options::OPT_fno_autolink,
                       Default);
 }
 
-static bool ShouldDisableDwarfDirectory(const ArgList &Args,
-                                        const ToolChain &TC) {
-  bool UseDwarfDirectory =
-      Args.hasFlag(options::OPT_fdwarf_directory_asm,
-                   options::OPT_fno_dwarf_directory_asm, TC.useIntegratedAs());
-  return !UseDwarfDirectory;
-}
-
 // Convert an arg of the form "-gN" or "-ggdbN" or one of their aliases
 // to the corresponding DebugInfoKind.
 static codegenoptions::DebugInfoKind DebugLevelToInfoKind(const Arg &A) {
   assert(A.getOption().matches(options::OPT_gN_Group) &&
          "Not a -g option that specifies a debug-info level");
   if (A.getOption().matches(options::OPT_g0) ||
       A.getOption().matches(options::OPT_ggdb0))
     return codegenoptions::NoDebugInfo;
if (Args.hasFlag(options::OPT_fdebug_types_section,
     } else if (checkDebugInfoOption(
                    Args.getLastArg(options::OPT_fdebug_types_section), Args, D,
                    TC)) {
       CmdArgs.push_back("-mllvm");
       CmdArgs.push_back("-generate-type-units");
     }
   }
 
+  // To avoid join/split of directory+filename, the integrated assembler prefers
+  // the directory form of .file on all DWARF versions. GNU as doesn't allow the
+  // form before DWARF v5.
+  if (!Args.hasFlag(options::OPT_fdwarf_directory_asm,
+                    options::OPT_fno_dwarf_directory_asm,
+                    TC.useIntegratedAs() || EffectiveDWARFVersion >= 5))
+    CmdArgs.push_back("-fno-dwarf-directory-asm");
+
   // Decide how to render forward declarations of template instantiations.
   // SCE wants full descriptions, others just get them in the name.
   if (DebuggerTuning == llvm::DebuggerKind::SCE)
     CmdArgs.push_back("-debug-forward-template-params");
 
   // Do we need to explicitly import anonymous namespaces into the parent
   // scope?
   if (DebuggerTuning == llvm::DebuggerKind::SCE)
#endif
   // Translate GCC's misnamer '-fasm' arguments to '-fgnu-keywords'.
   if (Arg *Asm = Args.getLastArg(options::OPT_fasm, options::OPT_fno_asm)) {
     if (Asm->getOption().matches(options::OPT_fasm))
       CmdArgs.push_back("-fgnu-keywords");
     else
       CmdArgs.push_back("-fno-gnu-keywords");
   }
 
-  if (ShouldDisableDwarfDirectory(Args, TC))
-    CmdArgs.push_back("-fno-dwarf-directory-asm");
-
   if (!ShouldEnableAutolink(Args, TC, JA))
     CmdArgs.push_back("-fno-autolink");
 
   // Add in -fdebug-compilation-dir if necessary.
   addDebugCompDirArg(Args, CmdArgs, D.getVFS());
 
   addDebugPrefixMapArg(D, Args, CmdArgs);
 

clang/test/Driver/debug-options.c

 // RUN:       | FileCheck -check-prefix=GDWARF64_32ARCH %s
 // RUN: %clang -### -c -gdwarf-4 -gdwarf64 -target x86_64-apple-darwin %s 2>&1 \
 // RUN:       | FileCheck -check-prefix=GDWARF64_ELF %s
 //
 // GDWARF64_ON:  "-gdwarf64"
 // GDWARF64_VER:  error: invalid argument '-gdwarf64' only allowed with 'DWARFv3 or greater'
 // GDWARF64_32ARCH: error: invalid argument '-gdwarf64' only allowed with '64 bit architecture'
 // GDWARF64_ELF: error: invalid argument '-gdwarf64' only allowed with 'ELF platforms'
+
+/// Default to -fno-dwarf-directory-asm for -fno-integrated-as before DWARF v5.
+// RUN: %clang -### -target x86_64 -c -gdwarf-2 %s 2>&1 | FileCheck --check-prefix=DIRECTORY %s
+// RUN: %clang -### -target x86_64 -c -gdwarf-5 %s 2>&1 | FileCheck --check-prefix=DIRECTORY %s
+// RUN: %clang -### -target x86_64 -c -gdwarf-4 -fno-integrated-as %s 2>&1 | FileCheck --check-prefix=NODIRECTORY %s
+// RUN: %clang -### -target x86_64 -c -gdwarf-5 -fno-integrated-as %s 2>&1 | FileCheck --check-prefix=DIRECTORY %s
+
+// RUN: %clang -### -target x86_64 -c -gdwarf-4 -fno-dwarf-directory-asm %s 2>&1 | FileCheck --check-prefix=NODIRECTORY %s
+
+// DIRECTORY-NOT: "-fno-dwarf-directory-asm"
+// NODIRECTORY: "-fno-dwarf-directory-asm"