[clang] Remove -g[no-]-* bool flags from g_Group (#162750)

There are four uses of BoolGOption, and all of them are essentially debug
info feature flags, which I believe should not the enablement or
disablement of all debug info emission. `OPT_g_group` is used to control
the debug info level here:

https://github.com/llvm/llvm-project/blob/main/clang/lib/Driver/ToolChains/Clang.cpp#L4387

This doesn't cause any test failures, and seems like the right behavior
for all four flags:
* -g[no-]flag-base
* -g[no-]inline-line-tables
* -g[no-]key-instructions
* -g[no-]structor-decl-linkage-names

None of these, even in the positive form, should enable debug info
emission.

Fixes #162747

Author: rnk

clang/include/clang/Driver/Options.td

@@ -545,15 +545,16 @@ multiclass BoolFOption<string flag_base, KeyPathAndMacro kpm,
               Group<f_Group>;
 }
 
-// Creates a BoolOption where both of the flags are prefixed with "g" and have
-// the Group<g_Group>.
+// Creates a BoolOption where both of the flags are prefixed with "g".
+// Does *not* map to g_Group, because that is reserved for flags that are
+// intended to enable (or disable) debug info, which is not appropriate for a
+// negative boolean flag (-gno-${feature}).
 // Used for -cc1 frontend options. Driver-only options do not map to
 // CompilerInvocation.
 multiclass BoolGOption<string flag_base, KeyPathAndMacro kpm,
                        Default default, FlagDef flag1, FlagDef flag2,
                        BothFlags both = BothFlags<[]>> {
-  defm NAME : BoolOption<"g", flag_base, kpm, default, flag1, flag2, both>,
-              Group<g_Group>;
+  defm NAME : BoolOption<"g", flag_base, kpm, default, flag1, flag2, both>;
 }
 
 multiclass BoolMOption<string flag_base, KeyPathAndMacro kpm,
@@ -4845,8 +4846,7 @@ defm structor_decl_linkage_names
                   NegFlag<SetFalse>,
                   PosFlag<SetTrue, [], [],
                           "Attach linkage names to C++ constructor/destructor "
-                          "declarations in DWARF."
-                          "Implies -g.">,
+                          "declarations in DWARF.">,
                   BothFlags<[], [ClangOption, CLOption, CC1Option]>>,
                   DocBrief<[{On some ABIs (e.g., Itanium), constructors and destructors may have multiple variants. Historically, when generating DWARF, Clang did not attach ``DW_AT_linkage_name`` to structor DIEs because there were multiple possible manglings (depending on the structor variant) that could be used. With ``-gstructor-decl-linkage-names``, for ABIs with structor variants, we attach a "unified" mangled name to structor declarations DIEs which debuggers can use to look up all the definitions for a structor declaration. E.g., a "unified" mangled name ``_ZN3FooC4Ev`` may have multiple definitions associated with it such as ``_ZN3FooC1Ev`` and ``_ZN3FooC2Ev``.
 
@@ -4855,7 +4855,7 @@ defm key_instructions : BoolGOption<"key-instructions",
     CodeGenOpts<"DebugKeyInstructions">, DefaultFalse,
     NegFlag<SetFalse>, PosFlag<SetTrue, [], [],
         "Enable Key Instructions, which reduces the jumpiness of debug stepping in optimized C/C++ code"
-        " in some debuggers. DWARF only. Implies -g.">,
+        " in some debuggers. DWARF only.">,
     BothFlags<[], [ClangOption, CLOption, CC1Option]>>;
 def headerpad__max__install__names : Joined<["-"], "headerpad_max_install_names">;
 def help : Flag<["-", "--"], "help">,

clang/test/DebugInfo/KeyInstructions/flag.cpp

@@ -1,12 +1,15 @@
 // RUN: %clang -### -target x86_64 -c -gdwarf -gkey-instructions %s 2>&1 | FileCheck %s --check-prefixes=KEY-INSTRUCTIONS
 // RUN: %clang -### -target x86_64 -c -gdwarf -gno-key-instructions %s 2>&1 | FileCheck %s --check-prefixes=NO-KEY-INSTRUCTIONS
+// RUN: %clang -### -target x86_64 -c -gno-key-instructions %s 2>&1 | FileCheck %s --check-prefixes=NO-DEBUG
 
 //// Help.
 // RUN %clang --help | FileCheck %s --check-prefix=HELP
-// HELP: -gkey-instructions  Enable Key Instructions, which reduces the jumpiness of debug stepping in optimized C/C++ code in some debuggers. DWARF only. Implies -g.
+// HELP: -gkey-instructions  Enable Key Instructions, which reduces the jumpiness of debug stepping in optimized C/C++ code in some debuggers. DWARF only.
 
 // KEY-INSTRUCTIONS: "-gkey-instructions"
 // NO-KEY-INSTRUCTIONS-NOT: key-instructions
+// NO-DEBUG-NOT: debug-info-kind
+// NO-DEBUG-NOT: dwarf
 
 //// Help hidden: flag should not be visible.
 // RUN: %clang --help | FileCheck %s --check-prefix=HELP

clang/test/Driver/debug-options.c

@@ -268,11 +268,11 @@
 // 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 -gomit-unreferenced-methods -fno-standalone-debug %s 2>&1 | FileCheck -check-prefix=INCTYPES %s
+// RUN: %clang -### -c -g -gomit-unreferenced-methods -fno-standalone-debug %s 2>&1 | FileCheck -check-prefix=INCTYPES %s
 // RUN: %clang -### -c %s 2>&1 | FileCheck -check-prefix=NOINCTYPES %s
-// RUN: %clang -### -c -gomit-unreferenced-methods -fdebug-types-section -target x86_64-unknown-linux %s 2>&1 \
+// RUN: %clang -### -c -g -gomit-unreferenced-methods -fdebug-types-section -target x86_64-unknown-linux %s 2>&1 \
 // RUN:        | FileCheck -check-prefix=NOINCTYPES %s
-// RUN: %clang -### -c -gomit-unreferenced-methods -fstandalone-debug %s 2>&1 | FileCheck -check-prefix=NOINCTYPES %s
+// RUN: %clang -### -c -g -gomit-unreferenced-methods -fstandalone-debug %s 2>&1 | FileCheck -check-prefix=NOINCTYPES %s
 //
 // RUN: %clang -### -c -glldb %s 2>&1 | FileCheck -check-prefix=NOPUB %s
 // RUN: %clang -### -c -glldb -gno-pubnames %s 2>&1 | FileCheck -check-prefix=NOPUB %s