[PATCH v2 1/4] Support for CodeView debugging format

This patch and the following add initial support for Microsoft's
CodeView debugging format, as used by MSVC, to mingw targets.

Note that you will need a recent version of binutils for this to be
useful. The best way to view the output is to run Microsoft's
cvdump.exe, found in their microsoft-pdb repo on GitHub, against the
object files.

gcc/

	* Makefile.in (OBJS): Add dwarf2codeview.o.
	(GTFILES): Add dwarf2codeview.cc
	* config/i386/cygming.h (CODEVIEW_DEBUGGING_INFO): Define.
	* dwarf2codeview.cc: New file.
	* dwarf2codeview.h: New file.
	* dwarf2out.cc: Include dwarf2codeview.h.
	(dwarf2out_finish): Call codeview_debug_finish as needed.
	* flag-types.h (DINFO_TYPE_CODEVIEW): Add enum member.
	(CODEVIEW_DEBUG): Define.
	* flags.h (codeview_debuginfo_p): Proottype.
	* opts.cc (debug_type_names): Add codeview.
	(debug_type_masks): Add CODEVIEW_DEBUG.
	(df_set_names): Add codeview.
	(codeview_debuginfo_p): New function.
	(dwarf_based_debuginfo_p): Add CODEVIEW clause.
	(set_debug_level): Handle CODEVIEW_DEBUG.
	* toplev.cc (process_options): Handle codeview.

gcc/testsuite
	* gcc.dg/debug/codeview/codeview-1.c: New test.
	* gcc.dg/debug/codeview/codeview.exp: New testsuite driver.

11 files changed, 177 insertions, 5 deletions

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index ecd5114..a7f1569 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1443,6 +1443,7 @@ OBJS = \
 	dumpfile.o \
 	dwarf2asm.o \
 	dwarf2cfi.o \
+	dwarf2codeview.o \
 	dwarf2ctf.o \
 	dwarf2out.o \
 	early-remat.o \
@@ -2838,6 +2839,7 @@ GTFILES = $(CPPLIB_H) $(srcdir)/input.h $(srcdir)/coretypes.h \
   $(srcdir)/dwarf2out.h \
   $(srcdir)/dwarf2asm.cc \
   $(srcdir)/dwarf2cfi.cc \
+  $(srcdir)/dwarf2codeview.cc \
   $(srcdir)/dwarf2ctf.cc \
   $(srcdir)/dwarf2out.cc \
   $(srcdir)/ctfc.h \
diff --git a/gcc/config/i386/cygming.h b/gcc/config/i386/cygming.h
index beedf7c..98b3755 100644
--- a/gcc/config/i386/cygming.h
+++ b/gcc/config/i386/cygming.h
@@ -20,6 +20,8 @@ along with GCC; see the file COPYING3.  If not see
 
 #define DWARF2_DEBUGGING_INFO 1
 
+#define CODEVIEW_DEBUGGING_INFO 1
+
 #undef PREFERRED_DEBUGGING_TYPE
 #define PREFERRED_DEBUGGING_TYPE DWARF2_DEBUG
 
diff --git a/gcc/dwarf2codeview.cc b/gcc/dwarf2codeview.cc
new file mode 100644
index 0000000..f08f5d5
--- /dev/null
+++ b/gcc/dwarf2codeview.cc
@@ -0,0 +1,54 @@
+/* Generate CodeView debugging info from the GCC DWARF.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+/* See gas/codeview.h in binutils for more about the constants and structs
+   listed below.  References to Microsoft files refer to Microsoft's PDB
+   repository: https://github.com/microsoft/microsoft-pdb.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "target.h"
+#include "output.h"
+#include "errors.h"
+#include "md5.h"
+#include "function.h"
+#include "version.h"
+#include "tree.h"
+#include "langhooks.h"
+#include "dwarf2out.h"
+#include "dwarf2codeview.h"
+
+#ifdef CODEVIEW_DEBUGGING_INFO
+
+#define CV_SIGNATURE_C13	4
+
+/* Finish CodeView debug info emission.  */
+
+void
+codeview_debug_finish (void)
+{
+  targetm.asm_out.named_section (".debug$S", SECTION_DEBUG, NULL);
+
+  fputs (integer_asm_op (4, false), asm_out_file);
+  fprint_whex (asm_out_file, CV_SIGNATURE_C13);
+  putc ('\n', asm_out_file);
+}
+
+#endif
diff --git a/gcc/dwarf2codeview.h b/gcc/dwarf2codeview.h
new file mode 100644
index 0000000..efda148
--- /dev/null
+++ b/gcc/dwarf2codeview.h
@@ -0,0 +1,30 @@
+/* dwarf2codeview.h - DWARF interface for CodeView generation.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_DWARF2CODEVIEW_H
+#define GCC_DWARF2CODEVIEW_H 1
+
+#include "dwarf2out.h"
+#include "flags.h"
+
+/* Debug Format Interface.  Used in dwarf2out.cc.  */
+
+extern void codeview_debug_finish (void);
+
+#endif /* GCC_DWARF2CODEVIEW_H */
diff --git a/gcc/dwarf2out.cc b/gcc/dwarf2out.cc
index 1b0e8b5..f7e9f90 100644
--- a/gcc/dwarf2out.cc
+++ b/gcc/dwarf2out.cc
@@ -80,6 +80,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "expr.h"
 #include "dwarf2out.h"
 #include "dwarf2ctf.h"
+#include "dwarf2codeview.h"
 #include "dwarf2asm.h"
 #include "toplev.h"
 #include "md5.h"
@@ -32278,6 +32279,11 @@ dwarf2out_finish (const char *filename)
        || btf_debuginfo_p ()) && lang_GNU_C ())
     ctf_debug_finish (filename);
 
+#ifdef CODEVIEW_DEBUGGING_INFO
+  if (codeview_debuginfo_p ())
+    codeview_debug_finish ();
+#endif
+
   /* Skip emitting DWARF if not required.  */
   if (!dwarf_debuginfo_p ())
     return;
diff --git a/gcc/flag-types.h b/gcc/flag-types.h
index 5062f59..5a2b461 100644
--- a/gcc/flag-types.h
+++ b/gcc/flag-types.h
@@ -29,6 +29,7 @@ enum debug_info_type
   DINFO_TYPE_VMS,		  /* VMS debug info.  */
   DINFO_TYPE_CTF,		  /* CTF debug info.  */
   DINFO_TYPE_BTF,		  /* BTF debug info.  */
+  DINFO_TYPE_CODEVIEW,		  /* CodeView debug info.  */
   DINFO_TYPE_BTF_WITH_CORE,	  /* BTF debug info with CO-RE relocations.  */
   DINFO_TYPE_MAX = DINFO_TYPE_BTF_WITH_CORE /* Marker only.  */
 };
@@ -42,6 +43,8 @@ enum debug_info_type
 #define CTF_DEBUG     (1U << DINFO_TYPE_CTF)
 /* Write BTF debug info (using btfout.cc).  */
 #define BTF_DEBUG     (1U << DINFO_TYPE_BTF)
+/* Write CodeView debug info (using dwarf2codeview.cc).  */
+#define CODEVIEW_DEBUG     (1U << DINFO_TYPE_CODEVIEW)
 /* Write BTF debug info for BPF CO-RE usecase (using btfout.cc).  */
 #define BTF_WITH_CORE_DEBUG     (1U << DINFO_TYPE_BTF_WITH_CORE)
 
diff --git a/gcc/flags.h b/gcc/flags.h
index b3f8e2e..52d6058 100644
--- a/gcc/flags.h
+++ b/gcc/flags.h
@@ -53,6 +53,10 @@ extern bool btf_with_core_debuginfo_p ();
 
 extern bool ctf_debuginfo_p ();
 
+/* Return true iff CodeView debug info is enabled.  */
+
+extern bool codeview_debuginfo_p ();
+
 /* Return true iff DWARF2 debug info is enabled.  */
 
 extern bool dwarf_debuginfo_p (struct gcc_options *opts = &global_options);
diff --git a/gcc/opts.cc b/gcc/opts.cc
index 3333600..b38d1e4 100644
--- a/gcc/opts.cc
+++ b/gcc/opts.cc
@@ -53,7 +53,7 @@ static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
 
 const char *const debug_type_names[] =
 {
-  "none", "dwarf-2", "vms", "ctf", "btf"
+  "none", "dwarf-2", "vms", "ctf", "btf", "codeview"
 };
 
 /* Bitmasks of fundamental debug info formats indexed by enum
@@ -62,13 +62,13 @@ const char *const debug_type_names[] =
 static uint32_t debug_type_masks[] =
 {
   NO_DEBUG, DWARF2_DEBUG, VMS_DEBUG,
-  CTF_DEBUG, BTF_DEBUG
+  CTF_DEBUG, BTF_DEBUG, CODEVIEW_DEBUG
 };
 
 /* Names of the set of debug formats requested by user.  Updated and accessed
    via debug_set_names.  */
 
-static char df_set_names[sizeof "none dwarf-2 vms ctf btf"];
+static char df_set_names[sizeof "none dwarf-2 vms ctf btf codeview"];
 
 /* Get enum debug_info_type of the specified debug format, for error messages.
    Can be used only for individual debug format types.  */
@@ -162,6 +162,14 @@ ctf_debuginfo_p ()
   return (write_symbols & CTF_DEBUG);
 }
 
+/* Return TRUE iff CodeView debug info is enabled.  */
+
+bool
+codeview_debuginfo_p ()
+{
+  return (write_symbols & CODEVIEW_DEBUG);
+}
+
 /* Return TRUE iff dwarf2 debug info is enabled.  */
 
 bool
@@ -176,7 +184,8 @@ dwarf_debuginfo_p (struct gcc_options *opts)
 bool dwarf_based_debuginfo_p ()
 {
   return ((write_symbols & CTF_DEBUG)
-	  || (write_symbols & BTF_DEBUG));
+	  || (write_symbols & BTF_DEBUG)
+	  || (write_symbols & CODEVIEW_DEBUG));
 }
 
 /* All flag uses below need to explicitely reference the option sets
@@ -3206,6 +3215,9 @@ common_handle_option (struct gcc_options *opts,
       break;
 
     case OPT_gcodeview:
+      set_debug_level (CODEVIEW_DEBUG, false, arg, opts, opts_set, loc);
+      if (opts->x_debug_info_level < DINFO_LEVEL_NORMAL)
+	opts->x_debug_info_level = DINFO_LEVEL_NORMAL;
       break;
 
     case OPT_gbtf:
@@ -3480,7 +3492,8 @@ set_debug_level (uint32_t dinfo, int extended, const char *arg,
 	    warning_at (loc, 0, "target system does not support debug output");
 	}
       else if ((opts->x_write_symbols & CTF_DEBUG)
-	       || (opts->x_write_symbols & BTF_DEBUG))
+	       || (opts->x_write_symbols & BTF_DEBUG)
+	       || (opts->x_write_symbols & CODEVIEW_DEBUG))
 	{
 	  opts->x_write_symbols |= DWARF2_DEBUG;
 	  opts_set->x_write_symbols |= DWARF2_DEBUG;
diff --git a/gcc/testsuite/gcc.dg/debug/codeview/codeview-1.c b/gcc/testsuite/gcc.dg/debug/codeview/codeview-1.c
new file mode 100644
index 0000000..eb5f145
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/codeview/codeview-1.c
@@ -0,0 +1,6 @@
+/* { dg-do compile } */
+/* { dg-options "-gcodeview" } */
+
+void func(void)
+{
+}
diff --git a/gcc/testsuite/gcc.dg/debug/codeview/codeview.exp b/gcc/testsuite/gcc.dg/debug/codeview/codeview.exp
new file mode 100644
index 0000000..ff705a4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/codeview/codeview.exp
@@ -0,0 +1,48 @@
+#   Copyright (C) 2023 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+# GCC testsuite that uses the `dg.exp' driver.
+
+# Load support procs.
+load_lib gcc-dg.exp
+
+if {![istarget i*86-*-mingw*]
+  && ![istarget x86_64-*-mingw*]} {
+    return 0
+}
+
+# If a testcase doesn't have special options, use these.
+global DEFAULT_CFLAGS
+if ![info exists DEFAULT_CFLAGS] then {
+    set DEFAULT_CFLAGS " -ansi -pedantic-errors"
+}
+
+# Initialize `dg'.
+dg-init
+
+# Main loop.
+set comp_output [gcc_target_compile \
+    "$srcdir/$subdir/../trivial.c" "trivial.S" assembly \
+    "additional_flags=-gcodeview"]
+if { ! [string match "*: target system does not support the * debug format*" \
+    $comp_output] } {
+    remove-build-file "trivial.S"
+    dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.\[cS\] ]] \
+	    "" $DEFAULT_CFLAGS
+}
+
+# All done.
+dg-finish
diff --git a/gcc/toplev.cc b/gcc/toplev.cc
index 2cd4096..bed1b0b 100644
--- a/gcc/toplev.cc
+++ b/gcc/toplev.cc
@@ -1438,6 +1438,10 @@ process_options ()
   else if (write_symbols == DWARF2_DEBUG)
     debug_hooks = &dwarf2_lineno_debug_hooks;
 #endif
+#ifdef CODEVIEW_DEBUGGING_INFO
+  else if (codeview_debuginfo_p ())
+    debug_hooks = &dwarf2_debug_hooks;
+#endif
   else
     {
       gcc_assert (debug_set_count (write_symbols) <= 1);