[PATCH] D52296: [Clang] - Add -fdwarf-fission=split,single option.

David Blaikie via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Wed Nov 7 07:54:30 PST 2018

dblaikie added a comment.

Thanks! - though on reflection I'm going to invoke @echristo again about the naming. It's unfortunately a bit backwards that the pre-standard flag is -gsplit-dwarf and what we're proposing as the standard flag is -fdwarf-fission, when the DWARF standard doesn't use the word "Fission" at all (only "split DWARF").

Maybe it'd be easy enough/better to add the "=single" suffix to the existing "-gsplit-dwarf"? (as much as I'm still a bit confused by which debug options use a '-g' and which ones use a '-f', etc).

Really sorry to go back/forth/around about on this, George.

Comment at: lib/Driver/ToolChains/Clang.cpp:2999-3001
+    StringRef Value = A->getOption().matches(options::OPT_fdwarf_fission_EQ)
+                          ? A->getValue()
+                          : "split";
Rather than creating a string in the case where there's no need for string matching/parsing, perhaps that could be avoided?

  if (!A->getOption().matches(options::OPT_fdwarf_fission_EQ))
    return DwarfFissionKind::Split;

  StringRef Value = A->getValue();
  if (Value == "split")

Comment at: lib/Driver/ToolChains/Clang.cpp:3010-3011
+  }
+  if (ArgIndex)
+    *ArgIndex = 0;
+  return DwarfFissionKind::None;
I'd probably either accept this as a precondition (assert(!ArgIndex || ArgIndex == 0)) or do this bit at the start of the function rather than the end here, to make it simpler/clearer that all paths assign some value to ArgIndex before exit of the function (even though that does mean checking/assigning ArgIndex unnecessarily in the case where the argument is given, etc)

Comment at: lib/Driver/ToolChains/Clang.cpp:5889
   const llvm::Triple &T = getToolChain().getTriple();
-  if (Args.hasArg(options::OPT_gsplit_dwarf) &&
+  if ((getDebugFissionKind(D, Args) == DwarfFissionKind::Split) &&
       (T.isOSLinux() || T.isOSFuchsia())) {
Could having more than one call to getDebugFissionKind lead to the error message (for -fdwarf-fission=garbage) being printed multiple times? Or is this call on a distinct/mutually exclusive codepath to the other?


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