[clang][AIX] Omitting Explicit Debugger Tuning Option

[qiongsiwu1]

Summary

On AIX, the default debugger is dbx so it is not necessary to explicitly set -debugger-tuning=dbx in the presence of -g.

[qiongsiwu1]

Adding one more test case.

[shchenz]

clang/lib/Driver/ToolChains/AIX.h

91

This sounds not right. Omitting -debugger-tuning=dbx does not mean we will change the default tuning debugger on AIX, right? i.e. DBX is still the default debugger on AIX no matter in the clang fe or llvm be.

We should just be able to do some customization when we call RenderDebugEnablingArgs for AIX in https://github.com/llvm/llvm-project/blob/main/clang/lib/Driver/ToolChains/Clang.cpp#L4367-L4368

[qiongsiwu1]

Address the review comment.

[shchenz]

LGTM except one minor in the testcase.

Thanks for adding this improvement.

clang/test/Driver/debug-options.c

121

nit: we can check that no -debugger-tuning= is emitted by check G_NOTUNING

[qiongsiwu1]

Adding two test cases to match G_NOTUNING.

[qiongsiwu1]

clang/test/Driver/debug-options.c

121

Ah thanks for catching this! Fixed.

[probinson]

clang/lib/Driver/ToolChains/Clang.cpp

4373

Seems like you should be able to return DebuggerKind::Default from getDefaultDebuggerTuning then you wouldn't need this complication?

[qiongsiwu1]

clang/lib/Driver/ToolChains/Clang.cpp

4373

Ah thanks for the suggestion!

We looked into an approach along this line in an earlier version (see https://reviews.llvm.org/D136187?id=468626), but it seemed that modifying the AIX default was not ideal. There are two drawbacks.

1. It complicates setting gstrict-dwarf and setting gno-column-info. The earlier version had to revise those conditions.
2. It may complicate future development that relies on the AIX tuning defaulting to DBX.

Therefore we ended up with this local change. That said, I am all ears for different ways to avoid the complication.

clang/lib/Driver/ToolChains/AIX.h

public:
   CXXStdlibType GetDefaultCXXStdlibType() const override;
 
   RuntimeLibType GetDefaultRuntimeLibType() const override;
 
   // Set default DWARF version to 3 for now as latest AIX OS supports version 3.
   unsigned GetDefaultDwarfVersion() const override { return 3; }
 
   llvm::DebuggerKind getDefaultDebuggerTuning() const override {
-    return llvm::DebuggerKind::DBX;
+    return llvm::DebuggerKind::Default;
   }
 
 protected:
   Tool *buildAssembler() const override;
   Tool *buildLinker() const override;
 
 private:
   llvm::StringRef GetHeaderSysroot(const llvm::opt::ArgList &DriverArgs) const;
   bool ParseInlineAsmUsingAsmParser;
 };
 
 } // end namespace toolchains
 } // end namespace driver
 } // end namespace clang
 
 #endif // LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_AIX_H

clang/lib/Driver/ToolChains/Clang.cpp

EffectiveDWARFVersion =
         std::min(RequestedDWARFVersion, TC.getMaxDwarfVersion());
   }
 
   // -gline-directives-only supported only for the DWARF debug info.
   if (RequestedDWARFVersion == 0 &&
       DebugInfoKind == codegenoptions::DebugDirectivesOnly)
     DebugInfoKind = codegenoptions::NoDebugInfo;
 
+  const bool UseDBX =
+      DebuggerTuning == llvm::DebuggerKind::DBX ||
+      (DebuggerTuning == llvm::DebuggerKind::Default && T.isOSAIX());
   // strict DWARF is set to false by default. But for DBX, we need it to be set
   // as true by default.
   if (const Arg *A = Args.getLastArg(options::OPT_gstrict_dwarf))
     (void)checkDebugInfoOption(A, Args, D, TC);
   if (Args.hasFlag(options::OPT_gstrict_dwarf, options::OPT_gno_strict_dwarf,
-                   DebuggerTuning == llvm::DebuggerKind::DBX))
+                   UseDBX)) {
     CmdArgs.push_back("-gstrict-dwarf");
+  }
 
   // And we handle flag -grecord-gcc-switches later with DWARFDebugFlags.
   Args.ClaimAllArgs(options::OPT_g_flags_Group);
 
   // Column info is included by default for everything except SCE 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, and the AIX
   // debugger DBX also doesn't handle the columns well, so it's better not to
   // include any column info.
   if (const Arg *A = Args.getLastArg(options::OPT_gcolumn_info))
     (void)checkDebugInfoOption(A, Args, D, TC);
   if (!Args.hasFlag(options::OPT_gcolumn_info, options::OPT_gno_column_info,
                     !EmitCodeView &&
-                        (DebuggerTuning != llvm::DebuggerKind::SCE &&
-                         DebuggerTuning != llvm::DebuggerKind::DBX)))
+                        (DebuggerTuning != llvm::DebuggerKind::SCE && !UseDBX)))
     CmdArgs.push_back("-gno-column-info");
 
   // FIXME: Move backend command line options to the module.
   // If -gline-tables-only or -gline-directives-only is the last option it wins.
   if (const Arg *A = Args.getLastArg(options::OPT_gmodules))
     if (checkDebugInfoOption(A, Args, D, TC)) {
       if (DebugInfoKind != codegenoptions::DebugLineTablesOnly &&
           DebugInfoKind != codegenoptions::DebugDirectivesOnly) {
if (willEmitRemarks(Args) &&
     DebugInfoKind = codegenoptions::DebugLineTablesOnly;
 
   // Adjust the debug info kind for the given toolchain.
   TC.adjustDebugInfoKind(DebugInfoKind, Args);
 
   RenderDebugEnablingArgs(Args, CmdArgs, DebugInfoKind, EffectiveDWARFVersion,
                           DebuggerTuning);
 
   // -fdebug-macro turns on macro debug info generation.
   if (Args.hasFlag(options::OPT_fdebug_macro, options::OPT_fno_debug_macro,
                    false))
     if (checkDebugInfoOption(Args.getLastArg(options::OPT_fdebug_macro), Args,
                              D, TC))
       CmdArgs.push_back("-debug-info-macro");
 
   // -ggnu-pubnames turns on gnu style pubnames in the backend.
   const auto *PubnamesArg =

clang/test/Driver/debug-options.c

 // RUN:             | FileCheck -check-prefix=SNLDTLTOGARANGE %s
 // RUN: %clang -### %s -g -flto=full -target x86_64-scei-ps4 2>&1 \
 // RUN:             | FileCheck -check-prefix=SNLDFLTOGARANGE %s
 // RUN: %clang -### %s -g -flto -target x86_64-scei-ps5 2>&1 \
 // RUN:             | FileCheck -check-prefix=LLDGARANGE %s
 // RUN: %clang -### %s -g -target x86_64-scei-ps5 2>&1 \
 // RUN:             | FileCheck -check-prefix=LDGARANGE %s
 
-// On the AIX, -g defaults to -gdbx and limited debug info.
+// On the AIX, -g defaults to limited debug info.
 // RUN: %clang -### -c -g %s -target powerpc-ibm-aix-xcoff 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_LIMITED -check-prefix=G_DBX %s
+// RUN:             | FileCheck -check-prefix=G_LIMITED %s
 // RUN: %clang -### -c -g %s -target powerpc64-ibm-aix-xcoff 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_LIMITED -check-prefix=G_DBX %s
+// RUN:             | FileCheck -check-prefix=G_LIMITED %s
+// RUN: %clang -### -c -g -gdbx %s -target powerpc-ibm-aix-xcoff 2>&1 \
+// RUN:             | FileCheck -check-prefixes=G_LIMITED,G_DBX %s
+// RUN: %clang -### -c -g -gdbx %s -target powerpc64-ibm-aix-xcoff 2>&1 \
+// RUN:             | FileCheck -check-prefixes=G_LIMITED,G_DBX %s
 
 // For DBX, -g defaults to -gstrict-dwarf.
 // RUN: %clang -### -c -g %s -target powerpc-ibm-aix-xcoff 2>&1 \
 // RUN:             | FileCheck -check-prefix=STRICT %s
 // RUN: %clang -### -c -g %s -target powerpc64-ibm-aix-xcoff 2>&1 \
 // RUN:             | FileCheck -check-prefix=STRICT %s
+// RUN: %clang -### -c -g -gdbx %s -target powerpc-ibm-aix-xcoff 2>&1 \
+// RUN:             | FileCheck -check-prefix=STRICT %s
+// RUN: %clang -### -c -g -gdbx %s -target powerpc64-ibm-aix-xcoff 2>&1 \
+// RUN:             | FileCheck -check-prefix=STRICT %s
 // RUN: %clang -### -c -g -gno-strict-dwarf %s -target powerpc-ibm-aix-xcoff \
 // RUN:             2>&1 | FileCheck -check-prefix=NOSTRICT %s
 // RUN: %clang -### -c -g %s -target x86_64-linux-gnu 2>&1 \
 // RUN:             | FileCheck -check-prefix=NOSTRICT %s
 // RUN: %clang -### -c -g -ggdb %s -target powerpc-ibm-aix-xcoff 2>&1 \
 // RUN:             | FileCheck -check-prefix=NOSTRICT %s
 
 // On the AIX, -g defaults to -gno-column-info.
 // RUN: %clang -### -c -g %s -target powerpc-ibm-aix-xcoff 2>&1 \
 // RUN:             | FileCheck -check-prefix=NOCI %s
 // RUN: %clang -### -c -g %s -target powerpc64-ibm-aix-xcoff 2>&1 \
 // RUN:             | FileCheck -check-prefix=NOCI %s
 // RUN: %clang -### -c -g %s -target powerpc-ibm-aix-xcoff -gcolumn-info 2>&1 \
 // RUN:             | FileCheck -check-prefix=CI %s
 // RUN: %clang -### -c -g %s -target powerpc64-ibm-aix-xcoff -gcolumn-info \
 // RUN:             2>&1 | FileCheck -check-prefix=CI %s
+// RUN: %clang -### -c -g -gdbx %s -target powerpc-ibm-aix-xcoff \
+// RUN:             -gcolumn-info 2>&1 | FileCheck -check-prefix=CI %s
+// RUN: %clang -### -c -g -gdbx %s -target powerpc64-ibm-aix-xcoff \
+// RUN:             -gcolumn-info 2>&1 | FileCheck -check-prefix=CI %s
 
 // WebAssembly.
 // WebAssembly should default to DWARF4.
 // RUN: %clang -### -c -g %s -target wasm32 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_DWARF4 %s
 // RUN: %clang -### -c -g %s -target wasm64 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_DWARF4 %s