DebugInfo: Add a driver flag for DWARF debug_ranges base address specifier use.

[dblaikie]

Summary

This saves a lot of relocations in optimized object files (at the cost
of some cost/increase in linked executable bytes), but gold's 32 bit
gdb-index support has a bug (
https://sourceware.org/bugzilla/show_bug.cgi?id=21894 ) so we can't
switch to this unconditionally. (& even if it weren't for that bug, one
might argue that some users would want to optimize in one direction or
the other - prioritizing object size or linked executable size)

Mostly sending this for review to bikeshed the flag name. (let's
bikeshed the IR names in the LLVM code review)

-fdwarf-base-address is my first prototype. Issues:

• Some existing flags (like -fdebug-types-section) use 'debug' rather than 'dwarf', but Clang supports formats other than dwarf, so perhaps names related to dwarf-specific features should have dwarf in the name, though it's unlikely GCC would ever be consistent with that goal?

• base addresses are part of DWARF even beyond this change (eg: range lists are relative to the CU's base address - which is somewhat unrelated to the base address specifiers used in the range list). So should this specifically call out that it's related to ranges? that it's base address /specifiers/ that are in use?

[echristo]

I have no other bikeshed colors here. :)

[dblaikie]

Settled on renaming the flag for consistency with, say, -fdebug-types-section, to -fdebug-ranges-base-address (though 'debug' is sort of ambiguous (Clang can produce non-DWARF debug info) but this driver (as opposed to clang-cl) is intended for DWARF emission, not PDB emission - and the "debug-ranges" part of the flag names the literal debug_ranges section (like debug-types refers to the debug_types section)).

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

def fallow_editor_placeholders : Flag<["-"], "fallow-editor-placeholders">,
   HelpText<"Treat editor placeholders as valid source code">;
 def fno_allow_editor_placeholders : Flag<["-"],
   "fno-allow-editor-placeholders">, Group<f_Group>;
 
 def fdebug_types_section: Flag <["-"], "fdebug-types-section">, Group<f_Group>,
   Flags<[CC1Option]>, HelpText<"Place debug types in their own section (ELF Only)">;
 def fno_debug_types_section: Flag<["-"], "fno-debug-types-section">, Group<f_Group>,
   Flags<[CC1Option]>;
+def fdebug_ranges_base_address: Flag <["-"], "fdebug-ranges-base-address">, Group<f_Group>,
+  Flags<[CC1Option]>, HelpText<"Use DWARF base address selection entries in debug_ranges">;
+def fno_debug_ranges_base_address: Flag <["-"], "fno-debug-ranges-base-address">, Group<f_Group>,
+  Flags<[CC1Option]>;
 def fsplit_dwarf_inlining: Flag <["-"], "fsplit-dwarf-inlining">, Group<f_Group>,
   Flags<[CC1Option]>, HelpText<"Provide minimal debug info in the object/executable to facilitate online symbolication/stack traces in the absence of .dwo/.dwp files when using Split DWARF">;
 def fno_split_dwarf_inlining: Flag<["-"], "fno-split-dwarf-inlining">, Group<f_Group>,
   Flags<[CC1Option]>;
 def fdebug_prefix_map_EQ
   : Joined<["-"], "fdebug-prefix-map=">, Group<f_Group>,
     Flags<[CC1Option,CC1AsOption]>,
     HelpText<"remap file source paths in debug info">;

cfe/trunk/include/clang/Frontend/CodeGenOptions.def

 CODEGENOPT(DebugInfoForProfiling, 1, 0)
 
 /// Whether 3-component vector type is preserved.
 CODEGENOPT(PreserveVec3Type, 1, 0)
 
 /// Whether to emit .debug_gnu_pubnames section instead of .debug_pubnames.
 CODEGENOPT(DebugNameTable, 2, 0)
 
+/// Whether to use DWARF base address specifiers in .debug_ranges.
+CODEGENOPT(DebugRangesBaseAddress, 1, 0)
+
 CODEGENOPT(NoPLT, 1, 0)
 
 /// Whether to embed source in DWARF debug line section.
 CODEGENOPT(EmbedSource, 1, 0)
 
 /// Whether to emit all vtables
 CODEGENOPT(ForceEmitVTables, 1, 0)
 

cfe/trunk/lib/CodeGen/CGDebugInfo.cpp

TheCU = DBuilder.createCompileUnit(
       CGOpts.EmitVersionIdentMetadata ? Producer : "",
       LO.Optimize || CGOpts.PrepareForLTO || CGOpts.PrepareForThinLTO,
       CGOpts.DwarfDebugFlags, RuntimeVers,
       CGOpts.EnableSplitDwarf ? "" : CGOpts.SplitDwarfFile, EmissionKind,
       0 /* DWOid */, CGOpts.SplitDwarfInlining, CGOpts.DebugInfoForProfiling,
       CGM.getTarget().getTriple().isNVPTX()
           ? llvm::DICompileUnit::DebugNameTableKind::None
           : static_cast<llvm::DICompileUnit::DebugNameTableKind>(
-                CGOpts.DebugNameTable));
+                CGOpts.DebugNameTable),
+      CGOpts.DebugRangesBaseAddress);
 }
 
 llvm::DIType *CGDebugInfo::CreateType(const BuiltinType *BT) {
   llvm::dwarf::TypeKind Encoding;
   StringRef BTName;
   switch (BT->getKind()) {
 #define BUILTIN_TYPE(Id, SingletonId)
 #define PLACEHOLDER_TYPE(Id, SingletonId) case BuiltinType::Id:

cfe/trunk/lib/Driver/ToolChains/Clang.cpp

if (SplitDWARFArg || DebuggerTuning == llvm::DebuggerKind::LLDB ||
     if (!PubnamesArg ||
         (!PubnamesArg->getOption().matches(options::OPT_gno_gnu_pubnames) &&
          !PubnamesArg->getOption().matches(options::OPT_gno_pubnames)))
       CmdArgs.push_back(PubnamesArg && PubnamesArg->getOption().matches(
                                            options::OPT_gpubnames)
                             ? "-gpubnames"
                             : "-ggnu-pubnames");
 
+  if (Args.hasFlag(options::OPT_fdebug_ranges_base_address,
+                   options::OPT_fno_debug_ranges_base_address, false)) {
+    CmdArgs.push_back("-fdebug-ranges-base-address");
+  }
+
   // -gdwarf-aranges turns on the emission of the aranges section in the
   // backend.
   // Always enabled for SCE tuning.
   bool NeedAranges = DebuggerTuning == llvm::DebuggerKind::SCE;
   if (const Arg *A = Args.getLastArg(options::OPT_gdwarf_aranges))
     NeedAranges = checkDebugInfoOption(A, Args, D, TC) || NeedAranges;
   if (NeedAranges) {
     CmdArgs.push_back("-mllvm");

cfe/trunk/lib/Frontend/CompilerInvocation.cpp

static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.DebugInfoForProfiling = Args.hasFlag(
       OPT_fdebug_info_for_profiling, OPT_fno_debug_info_for_profiling, false);
   Opts.DebugNameTable = static_cast<unsigned>(
       Args.hasArg(OPT_ggnu_pubnames)
           ? llvm::DICompileUnit::DebugNameTableKind::GNU
           : Args.hasArg(OPT_gpubnames)
                 ? llvm::DICompileUnit::DebugNameTableKind::Default
                 : llvm::DICompileUnit::DebugNameTableKind::None);
+  Opts.DebugRangesBaseAddress = Args.hasArg(OPT_fdebug_ranges_base_address);
 
   setPGOInstrumentor(Opts, Args, Diags);
   Opts.InstrProfileOutput =
       Args.getLastArgValue(OPT_fprofile_instrument_path_EQ);
   Opts.ProfileInstrumentUsePath =
       Args.getLastArgValue(OPT_fprofile_instrument_use_path_EQ);
   if (!Opts.ProfileInstrumentUsePath.empty())
     setPGOUseInstrumentor(Opts, Opts.ProfileInstrumentUsePath);

cfe/trunk/test/CodeGen/debug-info-ranges-base-address.c

+// RUN: %clang_cc1 -emit-llvm -debug-info-kind=limited %s -o - | FileCheck --check-prefix=NORNGBSE %s
+// RUN: %clang_cc1 -emit-llvm -debug-info-kind=limited %s -o - -fdebug-ranges-base-address | FileCheck --check-prefix=RNGBSE %s
+
+// NORNGBSE-NOT: rangesBaseAddress
+// RNGBSE: !DICompileUnit({{.*}}, rangesBaseAddress: true
+
+void f1() {
+}
+

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

 // RUN: %clang -### -c -gpubnames %s 2>&1 | FileCheck -check-prefix=PUB %s
 // RUN: %clang -### -c -ggdb %s 2>&1 | FileCheck -check-prefix=NOPUB %s
 // RUN: %clang -### -c -gpubnames -gno-gnu-pubnames %s 2>&1 | FileCheck -check-prefix=NOPUB %s
 // RUN: %clang -### -c -gpubnames -gno-pubnames %s 2>&1 | FileCheck -check-prefix=NOPUB %s
 //
 // RUN: %clang -### -c -gsplit-dwarf %s 2>&1 | FileCheck -check-prefix=GPUB %s
 // RUN: %clang -### -c -gsplit-dwarf -gno-pubnames %s 2>&1 | FileCheck -check-prefix=NOPUB %s
 //
+// RUN: %clang -### -c -fdebug-ranges-base-address %s 2>&1 | FileCheck -check-prefix=RNGBSE %s
+// RUN: %clang -### -c %s 2>&1 | FileCheck -check-prefix=NORNGBSE %s
+// RUN: %clang -### -c -fdebug-ranges-base-address -fno-debug-ranges-base-address %s 2>&1 | FileCheck -check-prefix=NORNGBSE %s
+//
 // RUN: %clang -### -c -glldb %s 2>&1 | FileCheck -check-prefix=GPUB %s
 // RUN: %clang -### -c -glldb -gno-pubnames %s 2>&1 | FileCheck -check-prefix=NOPUB %s
 //
 // RUN: %clang -### -c -gdwarf-aranges %s 2>&1 | FileCheck -check-prefix=GARANGE %s
 //
 // RUN: %clang -### -fdebug-types-section -target x86_64-unknown-linux %s 2>&1 \
 // RUN:        | FileCheck -check-prefix=FDTS %s
 //

 // GIGNORE-NOT: "argument unused during compilation"
 //
 // GPUB: -ggnu-pubnames
 // NOPUB-NOT: -ggnu-pubnames
 // NOPUB-NOT: -gpubnames
 //
 // PUB: -gpubnames
 //
+// RNGBSE: -fdebug-ranges-base-address
+// NORNGBSE-NOT: -fdebug-ranges-base-address
+//
 // GARANGE: -generate-arange-section
 //
 // FDTS: "-mllvm" "-generate-type-units"
 // FDTSE: error: unsupported option '-fdebug-types-section' for target 'x86_64-apple-darwin'
 //
 // NOFDTS-NOT: "-mllvm" "-generate-type-units"
 // NOFDTSE-NOT: error: unsupported option '-fdebug-types-section' for target 'x86_64-apple-darwin'
 //