Omit column info for CodeView by default

[amccarth]

Summary

Clang tracks only start columns, not start-end ranges. CodeView allows for that, but the VS debugger doesn't handle anything less than a complete range well--it either highlights the wrong part of a statement or truncates source lines in the assembly view. It's better to have no column information at all.

So by default, we'll omit the column information for CodeView targeting Windows.

Since the column info is still useful for sanitizers, I've promoted -gcolumn-info (and -gno-column-info) to a CoreOption and added a couple tests to make sure that works for clang-cl.

[rnk]

lgtm

cfe/trunk/include/clang/Driver/Options.td

 def gxcoff : Joined<["-"], "gxcoff">, Group<g_Group>, Flags<[Unsupported]>;
 def gvms : Joined<["-"], "gvms">, Group<g_Group>, Flags<[Unsupported]>;
 def gtoggle : Flag<["-"], "gtoggle">, Group<g_flags_Group>, Flags<[Unsupported]>;
 def grecord_gcc_switches : Flag<["-"], "grecord-gcc-switches">, Group<g_flags_Group>;
 def gno_record_gcc_switches : Flag<["-"], "gno-record-gcc-switches">,
   Group<g_flags_Group>;
 def gstrict_dwarf : Flag<["-"], "gstrict-dwarf">, Group<g_flags_Group>;
 def gno_strict_dwarf : Flag<["-"], "gno-strict-dwarf">, Group<g_flags_Group>;
-def gcolumn_info : Flag<["-"], "gcolumn-info">, Group<g_flags_Group>;
-def gno_column_info : Flag<["-"], "gno-column-info">, Group<g_flags_Group>;
+def gcolumn_info : Flag<["-"], "gcolumn-info">, Group<g_flags_Group>, Flags<[CoreOption]>;
+def gno_column_info : Flag<["-"], "gno-column-info">, Group<g_flags_Group>, Flags<[CoreOption]>;
 def gsplit_dwarf : Flag<["-"], "gsplit-dwarf">, Group<g_flags_Group>;
 def ggnu_pubnames : Flag<["-"], "ggnu-pubnames">, Group<g_flags_Group>;
 def gdwarf_aranges : Flag<["-"], "gdwarf-aranges">, Group<g_flags_Group>;
 def gmodules : Flag <["-"], "gmodules">, Group<f_Group>,
   HelpText<"Generate debug info with external references to clang modules"
            " or precompiled headers">;
 def headerpad__max__install__names : Joined<["-"], "headerpad_max_install_names">;
 def help : Flag<["-", "--"], "help">, Flags<[CC1Option,CC1AsOption]>,

cfe/trunk/lib/Driver/Tools.cpp

case llvm::Triple::x86_64:
     getX86TargetFeatures(D, Triple, Args, Features);
     break;
   case llvm::Triple::hexagon:
     getHexagonTargetFeatures(Args, Features);
     break;
   case llvm::Triple::wasm32:
   case llvm::Triple::wasm64:
     getWebAssemblyTargetFeatures(Args, Features);
-    break; 
+    break;
   case llvm::Triple::sparc:
   case llvm::Triple::sparcel:
   case llvm::Triple::sparcv9:
     getSparcTargetFeatures(D, Args, Features);
     break;
   case llvm::Triple::r600:
   case llvm::Triple::amdgcn:
     getAMDGPUTargetFeatures(D, Args, Features);
#endif
   } else if (DwarfVersion == 0 &&
              DebugInfoKind != codegenoptions::NoDebugInfo) {
     DwarfVersion = getToolChain().GetDefaultDwarfVersion();
   }
 
   // We ignore flags -gstrict-dwarf and -grecord-gcc-switches for now.
   Args.ClaimAllArgs(options::OPT_g_flags_Group);
 
-  // PS4 defaults to no column info
+  // Column info is included by default for everything except PS4 and CodeView.
+  // Clang doesn't track end columns, just starting columns, which, in theory,
+  // is fine for CodeView (and PDB).  In practice, however, the Microsoft
+  // debuggers don't handle missing end columns well, so it's better not to
+  // include any column info.
   if (Args.hasFlag(options::OPT_gcolumn_info, options::OPT_gno_column_info,
-                   /*Default=*/ !IsPS4CPU))
+                   /*Default=*/ !IsPS4CPU && !(IsWindowsMSVC && EmitCodeView)))
     CmdArgs.push_back("-dwarf-column-info");
 
   // FIXME: Move backend command line options to the module.
   if (Args.hasArg(options::OPT_gmodules)) {
     DebugInfoKind = codegenoptions::LimitedDebugInfo;
     CmdArgs.push_back("-dwarf-ext-refs");
     CmdArgs.push_back("-fmodule-format=obj");
   }
default:
     break;
 
   case llvm::Triple::mips:
   case llvm::Triple::mipsel:
   case llvm::Triple::mips64:
   case llvm::Triple::mips64el:
     AddMIPSTargetArgs(Args, CmdArgs);
     break;
-    
   case llvm::Triple::x86:
   case llvm::Triple::x86_64:
     AddX86TargetArgs(Args, CmdArgs);
     break;
   }
 
   // Consume all the warning flags. Usually this would be handled more
   // gracefully by -cc1 (warning about unknown warning flags, etc) but -cc1as

cfe/trunk/test/Driver/cl-options.c

 // RUN: %clang_cl /fp:fast /fp:precise -### -- %s 2>&1 | FileCheck -check-prefix=fpprecise %s
 // fpprecise-NOT: -menable-unsafe-fp-math
 // fpprecise-NOT: -ffast-math
 
 // RUN: %clang_cl /fp:fast /fp:strict -### -- %s 2>&1 | FileCheck -check-prefix=fpstrict %s
 // fpstrict-NOT: -menable-unsafe-fp-math
 // fpstrict-NOT: -ffast-math
 
+// RUN: %clang_cl /Z7 -gcolumn-info -### -- %s 2>&1 | FileCheck -check-prefix=gcolumn %s
+// gcolumn: -dwarf-column-info
+
+// RUN: %clang_cl /Z7 -gno-column-info -### -- %s 2>&1 | FileCheck -check-prefix=gnocolumn %s
+// gnocolumn-NOT: -dwarf-column-info
+
+// RUN: %clang_cl /Z7 -### -- %s 2>&1 | FileCheck -check-prefix=gdefcolumn %s
+// gdefcolumn-NOT: -dwarf-column-info
+
 // RUN: %clang_cl /GA -### -- %s 2>&1 | FileCheck -check-prefix=GA %s
 // GA: -ftls-model=local-exec
 
 // RTTI is on by default; just check that we don't error.
 // RUN: %clang_cl /Zs /GR -- %s 2>&1
 
 // RUN: %clang_cl /GR- -### -- %s 2>&1 | FileCheck -check-prefix=GR_ %s
 // GR_: -fno-rtti