[PATCH] Set a debugger "target" to guide DWARF choices

[Eric Christopher]

Some inline comments.

-eric


================
Comment at: include/llvm/CodeGen/CommandFlags.h:236
@@ +235,3 @@
+cl::opt<DebuggerKind>
+DebuggerTuning("debugger-tune",
+               cl::desc("Tune debug info for a particular debugger"),
----------------
probinson wrote:
> probinson wrote:
> > dblaikie wrote:
> > > What's the command line argument for? I mean convenience of testing LLVM, a bit, but in general we don't want to use backend options like this when actually interacting with LLVM from Clang and other frontends. This should probably end up as a part of the CU debug info metadata? Or a module-level debug info metadata flag? (ala DWARF version)
> > The command line option is precisely for testing; it is not how Clang communicates to LLVM.
> > CommandFlags.h exists to define command-line options for the tools (llc, opt etc) only.  It does not define a command-line option that is accessible to Clang.
> > Clang will set the TargetOptions field directly.
> > 
> David pointed out in email that using a TargetOptions field, it is hard to test that Clang got it right, and might not play nicely with LTO.  I'll look at doing it with module-level metadata.
> 
Module level metadata is a possibility if we think it's something that we'll need to make sure stays consistent at LTO time etc. You'll need to define a way for the metadata to merge, etc. I don't necessarily like encoding the data this way, but without a later LTO codegen pass we can pass options to it's your best bet.

================
Comment at: lib/CodeGen/AsmPrinter/DwarfDebug.cpp:222-223
@@ -212,3 +221,4 @@
+
   // Turn on accelerator tables for Darwin by default, pubnames by
-  // default for non-Darwin/PS4, and handle split dwarf.
+  // default for GDB, and handle split dwarf.
   if (DwarfAccelTables == Default)
----------------
Feel free to update this comment separately.

================
Comment at: lib/CodeGen/AsmPrinter/DwarfDebug.cpp:245
@@ -234,3 +244,3 @@
   // Everybody else uses GNU's.
-  UseGNUTLSOpcode = !(IsDarwin || IsPS4) || DwarfVersion < 3;
+  UseGNUTLSOpcode = !(IsDarwin || TT.isPS4CPU()) || DwarfVersion < 3;
 
----------------
I don't like the use of TT.isPS4CPU() here on first look, can you explain a bit?

http://reviews.llvm.org/D8506

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