[Debug-Info] Use inlined strings in .dwinfo section by default for DBX.

[Esme]

Summary

This is a minor patch to set the default DwarfInlinedStrings as inlined strings for DBX, due to DBX does not support .dwstr section for now.

[shchenz]

Can we set this only for DBX? This should be a limitation for DBX not for AIX?

[Esme]

llvm/lib/CodeGen/CommandFlags.cpp

417

Thanks for @shchenz's comments.
We have added tuning debugger option DBX in D99400, but missed adding it to llc/opt command flags, which is a one-line change, so I also do it in this patch as well. Is it ok?

[dblaikie]

llvm/test/DebugInfo/XCOFF/dbx-inlinedstrings.ll

32–33

I'd probably put these CHECK lines up the top near the RUN line - and flesh them out a bit, maybe? Oh, and in the RUN line, run llc to an object, run the object through llvm-dwarfdump rather than checking the assembly directly. Possibly use implicit-check-not DW_FORM_strp, and explicitly check where the DW_FORM_string turns up (perhaps dump debug_info in verbose mode, and check, for instance that the DW_AT_producer is in the right form and has the right value)

(do you have a pointer to the testing that was originally added for this feature when it was introduced for NVPTX? Might be worth comparing it/seeing if there's some inspiration there)

[shchenz]

llvm/lib/CodeGen/CommandFlags.cpp

417

The change here is for controlling the inlined string for llc. It is not necessary. Normally, when you compile source files by using clang, clang FE will set the debugger type for you. You should already test this, right?

Wth this change, now you can test the inlined string settings only with llc.

[Esme]

Addressed comments.

llvm/lib/CodeGen/CommandFlags.cpp

417

I've verified both of clang -gdbx under Linux and clang -g under AIX, and clang FE works well for them.

llvm/test/DebugInfo/XCOFF/dbx-inlinedstrings.ll

32–33

The feature for NVPTX introduced in D41827 is not the main purpose in that patch, so the whole assembly was checked directly there.

[dblaikie]

llvm/test/DebugInfo/XCOFF/dbx-inlinedstrings.ll

32–33

fair enough - thanks for the test update, it's probably a bit overkill here. Testing just the DW_AT_producer, for instance, seems like it'd be good enough to demonstrate the use of FORM_string and the value. No need to test a bunch of other (especially non-string) attributes (that sort of testing can make the test brittle - if we add new attributes, reorder attributes, etc, this test would need to be updated despite the functionality it intends to test not having changed)

[Esme]

Removed unnecessary checks.

@dblaikie Thanks! Your advice makes sense to me.

[dblaikie]

Looks good - thanks!

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h

public:
 
   /// \defgroup DebuggerTuning Predicates to tune DWARF for a given debugger.
   ///
   /// Returns whether we are "tuning" for a given debugger.
   /// @{
   bool tuneForGDB() const { return DebuggerTuning == DebuggerKind::GDB; }
   bool tuneForLLDB() const { return DebuggerTuning == DebuggerKind::LLDB; }
   bool tuneForSCE() const { return DebuggerTuning == DebuggerKind::SCE; }
+  bool tuneForDBX() const { return DebuggerTuning == DebuggerKind::DBX; }
   /// @}
 
   const MCSymbol *getSectionLabel(const MCSection *S);
   void insertSectionLabel(const MCSymbol *S);
 
   static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
                                 const DbgValueLoc &Value,
                                 DwarfExpression &DwarfExpr);

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

DwarfDebug::DwarfDebug(AsmPrinter *A)
   else if (IsDarwin)
     DebuggerTuning = DebuggerKind::LLDB;
   else if (TT.isPS4CPU())
     DebuggerTuning = DebuggerKind::SCE;
   else
     DebuggerTuning = DebuggerKind::GDB;
 
   if (DwarfInlinedStrings == Default)
-    UseInlineStrings = TT.isNVPTX();
+    UseInlineStrings = TT.isNVPTX() || tuneForDBX();
   else
     UseInlineStrings = DwarfInlinedStrings == Enable;
 
   UseLocSection = !TT.isNVPTX();
 
   HasAppleExtensionAttributes = tuneForLLDB();
 
   // Handle split DWARF.

llvm/lib/CodeGen/CommandFlags.cpp

#define CGBINDOPT(NAME)                                                        \
   CGBINDOPT(EABIVersion);
 
   static cl::opt<DebuggerKind> DebuggerTuningOpt(
       "debugger-tune", cl::desc("Tune debug info for a particular debugger"),
       cl::init(DebuggerKind::Default),
       cl::values(
           clEnumValN(DebuggerKind::GDB, "gdb", "gdb"),
           clEnumValN(DebuggerKind::LLDB, "lldb", "lldb"),
+          clEnumValN(DebuggerKind::DBX, "dbx", "dbx"),
           clEnumValN(DebuggerKind::SCE, "sce", "SCE targets (e.g. PS4)")));
   CGBINDOPT(DebuggerTuningOpt);
 
   static cl::opt<bool> EnableStackSizeSection(
       "stack-size-section",
       cl::desc("Emit a section containing stack size metadata"),
       cl::init(false));
   CGBINDOPT(EnableStackSizeSection);

llvm/test/DebugInfo/XCOFF/dbx-inlinedstrings.ll

+; RUN: llc -debugger-tune=dbx -dwarf-version=3 < %s | FileCheck %s
+
+source_filename = "1.c"
+target datalayout = "E-m:a-p:32:32-i64:64-n32"
+
+; Function Attrs: noinline nounwind optnone
+define i32 @main() #0 !dbg !8 {
+entry:
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  ret i32 0, !dbg !12
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 12.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "1.c", directory: "debug")
+!2 = !{}
+!3 = !{i32 7, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 12.0.0"}
+!8 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 1, type: !9, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!9 = !DISubroutineType(types: !10)
+!10 = !{!11}
+!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!12 = !DILocation(line: 3, column: 3, scope: !8)
+
+; CHECK-NOT: DW_FORM_strp
+; CHECK: DW_FORM_string