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

George Rimar via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Thu Nov 8 02:38:59 PST 2018

grimar added inline comments.

Comment at: lib/Driver/ToolChains/Clang.cpp:2999-3001
+    StringRef Value = A->getOption().matches(options::OPT_fdwarf_fission_EQ)
+                          ? A->getValue()
+                          : "split";
dblaikie wrote:
> 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;
dblaikie wrote:
> 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)
It turns out that `A->getIndex()` returned can be different from index in `Args` array. 
So it is not correct to use something like `size_t Index = A->getIndex(); ....;  Arg* A = Args.getArgs()[Index]`.

I rewrote this method.

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())) {
dblaikie wrote:
> 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?
I think it should not be possible. Currently, there are 2 inclusions of the `getDebugFissionKind `. One is used for construction clang job,
and one is here, it is used to construct an assembler tool job. I do not see a way how it can be printed multiple times.

For example, the following invocation will print it only once:

clang main.c -o out.s -S -fdwarf-fission=foo
clang-8: error: unsupported argument 'foo' to option 'fdwarf-fission='


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