Add new -fverbose-asm that enables source interleaving

[rogfer01]

Summary

This is the clang side of the RFC in http://lists.llvm.org/pipermail/cfe-dev/2017-February/052549.html

Note that in contrast to the original suggestion -fsource-asm here we use the preferred -fverbose-asm. Basically explicitly saying -fverbose-asm in the command line enables a minimum amount of debugging, so in AsmPrinter we can use it to print the source code.

This patch introduces a -masm-source flag for cc1 that maps to the AsmSource value in the llvm code generation.

See the llvm side of this in https://reviews.llvm.org/D30897

TODO: Testing

[andreybokhanko]

Hi Roger,

I'm very glad to see you started to work on this!

A somewhat obvious comment: no chance for this to be accepted without LIT tests. I understand you have your doubts on the best approach to testing -- and it's OK to ask either here or on llvm-dev -- but tests should be added nevertheless.

Yours,
Andrey

[rogfer01]

A somewhat obvious comment: no chance for this to be accepted without LIT tests. I understand you have your doubts on the best approach to testing -- and it's OK to ask either here or on llvm-dev -- but tests should be added nevertheless.

Sure. I wasn't planning to commit this without tests! :)

Thank you.

[hfinkel]

Note that in contrast to the original suggestion -fsource-asm here we use the preferred -fverbose-asm. Basically explicitly saying -fverbose-asm in the command line enables a minimum amount of debugging, so in AsmPrinter we can use it to print the source code.

-fverbose-asm seems like a good name to me, but that's taken already. This feature should imply -fverbose-asm (that's where the value-add is over having objdump do this). But we don't always want this when we enable -fverbose-asm. How about -fsource-interleaved-asm for this feature?

This patch introduces a -masm-source flag for cc1 that maps to the AsmSource value in the llvm code generation.

I see no reason to use a different flag name for cc1. Just use the same flag (tag it with Flags<[CC1Option] in the .td file).

lib/Driver/ToolChains/Clang.cpp

2754

I think that we should factor this out a bit. This feature is not the only one with this problem. The optimization reporting features also have this property (they need to enable debug info for some reason other than an actual desire to embed debug info in the resulting binaries). I think that we should add some separate feature, which this can toggle, but that optimization reporting can also use, to avoid actually generating debug info when only needed by these features.

lib/Frontend/CompilerInvocation.cpp

855

This is where you'd enable debug line-table info when needed by this feature.

include/clang/Driver/CC1Options.td

 def fuse_register_sized_bitfield_access: Flag<["-"], "fuse-register-sized-bitfield-access">,
   HelpText<"Use register sized accesses to bit-fields, when possible.">;
 def relaxed_aliasing : Flag<["-"], "relaxed-aliasing">,
   HelpText<"Turn off Type Based Alias Analysis">;
 def no_struct_path_tbaa : Flag<["-"], "no-struct-path-tbaa">,
   HelpText<"Turn off struct-path aware Type Based Alias Analysis">;
 def masm_verbose : Flag<["-"], "masm-verbose">,
   HelpText<"Generate verbose assembly output">;
+def masm_source : Separate<["-"], "masm-source">,
+  HelpText<"Annotate assembly output with source code lines.">;
 def mcode_model : Separate<["-"], "mcode-model">,
   HelpText<"The code model to use">;
 def mdebug_pass : Separate<["-"], "mdebug-pass">,
   HelpText<"Enable additional debug output">;
 def mdisable_fp_elim : Flag<["-"], "mdisable-fp-elim">,
   HelpText<"Disable frame pointer elimination optimization">;
 def mdisable_tail_calls : Flag<["-"], "mdisable-tail-calls">,
   HelpText<"Disable tail call optimization, keeping the call stack accurate">;

include/clang/Frontend/CodeGenOptions.def

 #  define ENUM_CODEGENOPT(Name, Type, Bits, Default) \
 CODEGENOPT(Name, Bits, Default)
 #endif
 
 CODEGENOPT(DisableIntegratedAS, 1, 0) ///< -no-integrated-as
 CODEGENOPT(CompressDebugSections, 1, 0) ///< -Wa,-compress-debug-sections
 CODEGENOPT(RelaxELFRelocations, 1, 0) ///< -Wa,--mrelax-relocations
 CODEGENOPT(AsmVerbose        , 1, 0) ///< -dA, -fverbose-asm.
+CODEGENOPT(AsmSource         , 2, 0) ///< -fverbose-asm.
 CODEGENOPT(PreserveAsmComments, 1, 1) ///< -dA, -fno-preserve-as-comments.
 CODEGENOPT(AssumeSaneOperatorNew , 1, 1) ///< implicit __attribute__((malloc)) operator new
 CODEGENOPT(Autolink          , 1, 1) ///< -fno-autolink
 CODEGENOPT(ObjCAutoRefCountExceptions , 1, 0) ///< Whether ARC should be EH-safe.
 CODEGENOPT(Backchain         , 1, 0) ///< -mbackchain
 CODEGENOPT(CoverageExtraChecksum, 1, 0) ///< Whether we need a second checksum for functions in GCNO files.
 CODEGENOPT(CoverageNoFunctionNamesInData, 1, 0) ///< Do not include function names in GCDA files.
 CODEGENOPT(CoverageExitBlockBeforeBody, 1, 0) ///< Whether to emit the exit block before the body blocks in GCNO files.

lib/CodeGen/BackendUtil.cpp

void EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
   Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
   Options.MCOptions.MCUseDwarfDirectory = !CodeGenOpts.NoDwarfDirectoryAsm;
   Options.MCOptions.MCNoExecStack = CodeGenOpts.NoExecStack;
   Options.MCOptions.MCIncrementalLinkerCompatible =
       CodeGenOpts.IncrementalLinkerCompatible;
   Options.MCOptions.MCPIECopyRelocations = CodeGenOpts.PIECopyRelocations;
   Options.MCOptions.MCFatalWarnings = CodeGenOpts.FatalWarnings;
   Options.MCOptions.AsmVerbose = CodeGenOpts.AsmVerbose;
+  Options.MCOptions.AsmSource = CodeGenOpts.AsmSource;
   Options.MCOptions.PreserveAsmComments = CodeGenOpts.PreserveAsmComments;
   Options.MCOptions.ABIName = TargetOpts.ABI;
   for (const auto &Entry : HSOpts.UserEntries)
     if (!Entry.IsFramework &&
         (Entry.Group == frontend::IncludeDirGroup::Quoted ||
          Entry.Group == frontend::IncludeDirGroup::Angled ||
          Entry.Group == frontend::IncludeDirGroup::System))
       Options.MCOptions.IASSearchPaths.push_back(

lib/Driver/ToolChains/Clang.cpp

if (getToolChain().getTriple().isOSLinux() && SplitDwarfArg) {
     if (!splitDwarfInlining)
       CmdArgs.push_back("-fno-split-dwarf-inlining");
     if (DebugInfoKind == codegenoptions::NoDebugInfo)
       DebugInfoKind = codegenoptions::LimitedDebugInfo;
     CmdArgs.push_back("-backend-option");
     CmdArgs.push_back("-split-dwarf=Enable");
   }
 
+  // If -fverbose-asm explicitly appears enable at least DebugLineTablesOnly
+  // but remember that no debug info was requested, to avoid cluttering
+  // assembler output with debug directives.
+  if (Args.hasArg(options::OPT_fverbose_asm)) {
+    CmdArgs.push_back("-masm-source");
+    if (DebugInfoKind == codegenoptions::NoDebugInfo) {
+      // FIXME: Check whether LimitedDebugInfo will give us line information,
+      // otherwise we should be overriding it as well.
+      DebugInfoKind = codegenoptions::DebugLineTablesOnly;
+      CmdArgs.push_back("1");
+    } else
+      CmdArgs.push_back("2");
+  }
+
   // After we've dealt with all combinations of things that could
   // make DebugInfoKind be other than None or DebugLineTablesOnly,
   // figure out if we need to "upgrade" it to standalone debug info.
   // We parse these two '-f' options whether or not they will be used,
   // to claim them even if you wrote "-fstandalone-debug -gline-tables-only"
   bool NeedFullDebug = Args.hasFlag(options::OPT_fstandalone_debug,
                                     options::OPT_fno_standalone_debug,
                                     getToolChain().GetDefaultStandaloneDebug());

lib/Frontend/CompilerInvocation.cpp

Opts.ProfileInstrumentUsePath =
       Args.getLastArgValue(OPT_fprofile_instrument_use_path_EQ);
   if (!Opts.ProfileInstrumentUsePath.empty())
     setPGOUseInstrumentor(Opts, Opts.ProfileInstrumentUsePath);
 
   Opts.CoverageMapping =
       Args.hasFlag(OPT_fcoverage_mapping, OPT_fno_coverage_mapping, false);
   Opts.DumpCoverageMapping = Args.hasArg(OPT_dump_coverage_mapping);
   Opts.AsmVerbose = Args.hasArg(OPT_masm_verbose);
+  Opts.AsmSource = getLastArgIntValue(Args, OPT_masm_source, 0, Diags);
   Opts.PreserveAsmComments = !Args.hasArg(OPT_fno_preserve_as_comments);
   Opts.AssumeSaneOperatorNew = !Args.hasArg(OPT_fno_assume_sane_operator_new);
   Opts.ObjCAutoRefCountExceptions = Args.hasArg(OPT_fobjc_arc_exceptions);
   Opts.CXAAtExit = !Args.hasArg(OPT_fno_use_cxa_atexit);
   Opts.CXXCtorDtorAliases = Args.hasArg(OPT_mconstructor_aliases);
   Opts.CodeModel = getCodeModel(Args, Diags);
   Opts.DebugPass = Args.getLastArgValue(OPT_mdebug_pass);
   Opts.DisableFPElim =
static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
 
   Opts.DependentLibraries = Args.getAllArgValues(OPT_dependent_lib);
   Opts.LinkerOptions = Args.getAllArgValues(OPT_linker_option);
   bool NeedLocTracking = false;
 
   Opts.OptRecordFile = Args.getLastArgValue(OPT_opt_record_file);
   if (!Opts.OptRecordFile.empty())
     NeedLocTracking = true;
 
   if (Arg *A = Args.getLastArg(OPT_Rpass_EQ)) {
     Opts.OptimizationRemarkPattern =
         GenerateOptimizationRemarkRegex(Diags, Args, A);
     NeedLocTracking = true;
   }
 
   if (Arg *A = Args.getLastArg(OPT_Rpass_missed_EQ)) {
     Opts.OptimizationRemarkMissedPattern =