debug/96383 - emit debug info for used external functions

This makes sure to emit full declaration DIEs including
formal parameters for used external functions.  This helps
debugging when debug information of the external entity is
not available and also helps external tools cross-checking
ABI compatibility which was the bug reporters use case.

For cc1 this affects debug information size as follows:

     VM SIZE                     FILE SIZE
 ++++++++++++++ GROWING       ++++++++++++++
  [ = ]       0 .debug_info   +1.63Mi  +1.3%
  [ = ]       0 .debug_str     +263Ki  +3.4%
  [ = ]       0 .debug_abbrev  +101Ki  +4.9%
  [ = ]       0 .debug_line   +5.71Ki  +0.0%
   +44%     +16 [Unmapped]        +48  +1.2%

 -------------- SHRINKING     --------------
  [ = ]       0 .debug_loc       -213  -0.0%
  -0.0%     -48 .text             -48  -0.0%
  [ = ]       0 .debug_ranges     -16  -0.0%

  -0.0%     -32 TOTAL         +1.99Mi  +0.6%

and DWARF compression via DWZ can only shave off minor bits
here.

Previously we emitted no DIEs for external functions at all
unless they were referenced via DW_TAG_GNU_call_site which
for some GCC revs caused a regular DIE to appear and since
GCC 4.9 only a stub without formal parameters.  This means
at -O0 we did not emit any DIE for external functions
but with optimization we emitted stubs.

2020-07-30  Richard Biener  <rguenther@suse.de>

	PR debug/96383
	* langhooks-def.h (lhd_finalize_early_debug): Declare.
	(LANG_HOOKS_FINALIZE_EARLY_DEBUG): Define.
	(LANG_HOOKS_INITIALIZER): Amend.
	* langhooks.c: Include cgraph.h and debug.h.
	(lhd_finalize_early_debug): Default implementation from
	former code in finalize_compilation_unit.
	* langhooks.h (lang_hooks::finalize_early_debug): Add.
	* cgraphunit.c (symbol_table::finalize_compilation_unit):
	Call the finalize_early_debug langhook.

gcc/c-family/
	* c-common.h (c_common_finalize_early_debug): Declare.
	* c-common.c: Include debug.h.
	(c_common_finalize_early_debug): finalize_early_debug langhook
	implementation generating debug for extern declarations.

gcc/c/
	* c-objc-common.h (LANG_HOOKS_FINALIZE_EARLY_DEBUG):
	Define to c_common_finalize_early_debug.

gcc/cp/
	* cp-objcp-common.h (LANG_HOOKS_FINALIZE_EARLY_DEBUG):
	Define to c_common_finalize_early_debug.

gcc/testsuite/
	* gcc.dg/debug/dwarf2/pr96383-1.c: New testcase.
	* gcc.dg/debug/dwarf2/pr96383-2.c: Likewise.

libstdc++-v3/
	* testsuite/20_util/assume_aligned/3.cc: Use -g0.

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 116867a4513cfd2838f76a2eb6b9de8f6ea28238..b97539c0c2aa88c9743108b4b5e34cfab5cafaf3 100644 (file)
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -50,6 +50,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "spellcheck.h"
 #include "c-spellcheck.h"
 #include "selftest.h"
+#include "debug.h"
 
 cpp_reader *parse_in;          /* Declared in c-pragma.h.  */
 
@@ -9086,4 +9087,20 @@ braced_lists_to_strings (tree type, tree ctor)
   return braced_lists_to_strings (type, ctor, false);
 }
 
+
+/* Emit debug for functions before finalizing early debug.  */
+
+void
+c_common_finalize_early_debug (void)
+{
+  /* Emit early debug for reachable functions, and by consequence,
+     locally scoped symbols.  Also emit debug for extern declared
+     functions that are still reachable at this point.  */
+  struct cgraph_node *cnode;
+  FOR_EACH_FUNCTION (cnode)
+    if (!cnode->alias && !cnode->thunk.thunk_p
+       && (cnode->has_gimple_body_p () || !DECL_IS_BUILTIN (cnode->decl)))
+      (*debug_hooks->early_global_decl) (cnode->decl);
+}
+
 #include "gt-c-family-c-common.h"

diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 61627264e1ec273a25f2b3659c09087ea673c0a6..4fc64bc4aa64d4409b73bc532bd9db5ef7f7de5b 100644 (file)
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -885,6 +885,8 @@ extern bool bool_promoted_to_int_p (tree);
 extern tree fold_for_warn (tree);
 extern tree c_common_get_narrower (tree, int *);
 extern bool get_attribute_operand (tree, unsigned HOST_WIDE_INT *);
+extern void c_common_finalize_early_debug (void);
+
 
 #define c_sizeof(LOC, T)  c_sizeof_or_alignof_type (LOC, T, true, false, 1)
 #define c_alignof(LOC, T) c_sizeof_or_alignof_type (LOC, T, false, false, 1)

diff --git a/gcc/c/c-objc-common.h b/gcc/c/c-objc-common.h
index 5471fc7e35519d30ef25c7bcf1c804c9fc490c27..925795986e785366fe5ee610c4dd1ce0e249e15e 100644 (file)
--- a/gcc/c/c-objc-common.h
+++ b/gcc/c/c-objc-common.h
@@ -65,6 +65,8 @@ along with GCC; see the file COPYING3.  If not see
   c_simulate_builtin_function_decl
 #undef LANG_HOOKS_EMITS_BEGIN_STMT
 #define LANG_HOOKS_EMITS_BEGIN_STMT true
+#undef LANG_HOOKS_FINALIZE_EARLY_DEBUG
+#define LANG_HOOKS_FINALIZE_EARLY_DEBUG c_common_finalize_early_debug
 
 /* Attribute hooks.  */
 #undef LANG_HOOKS_COMMON_ATTRIBUTE_TABLE

diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
index 0a95eb93ce2d05d7dbca04644d13ae96f594b413..0b1009d0dea14e9546e3d2a696c602f88005b814 100644 (file)
--- a/gcc/cgraphunit.c
+++ b/gcc/cgraphunit.c
@@ -2998,11 +2998,9 @@ symbol_table::finalize_compilation_unit (void)
 
   if (!seen_error ())
     {
-      /* Emit early debug for reachable functions, and by consequence,
-        locally scoped symbols.  */
-      struct cgraph_node *cnode;
-      FOR_EACH_FUNCTION_WITH_GIMPLE_BODY (cnode)
-       (*debug_hooks->early_global_decl) (cnode->decl);
+      /* Give the frontends the chance to emit early debug based on
+        what is still reachable in the TU.  */
+      (*lang_hooks.finalize_early_debug) ();
 
       /* Clean up anything that needs cleaning up after initial debug
         generation.  */

diff --git a/gcc/cp/cp-objcp-common.h b/gcc/cp/cp-objcp-common.h
index de8d606fe2c9e7ad6b172b26222213eca218b6ab..0936f166d5b7694ea5e39cc52e881e30c48548bb 100644 (file)
--- a/gcc/cp/cp-objcp-common.h
+++ b/gcc/cp/cp-objcp-common.h
@@ -115,6 +115,8 @@ extern tree cxx_simulate_enum_decl (location_t, const char *,
 #define LANG_HOOKS_BLOCK_MAY_FALLTHRU cxx_block_may_fallthru
 #undef LANG_HOOKS_EMITS_BEGIN_STMT
 #define LANG_HOOKS_EMITS_BEGIN_STMT true
+#undef LANG_HOOKS_FINALIZE_EARLY_DEBUG
+#define LANG_HOOKS_FINALIZE_EARLY_DEBUG c_common_finalize_early_debug
 
 /* Attribute hooks.  */
 #undef LANG_HOOKS_COMMON_ATTRIBUTE_TABLE

diff --git a/gcc/langhooks-def.h b/gcc/langhooks-def.h
index 6e4e2cc9367d3f5eca5f43af8a8c3552975f7e81..67b02107c495dcf638af1a043ec55889558c1fd9 100644 (file)
--- a/gcc/langhooks-def.h
+++ b/gcc/langhooks-def.h
@@ -92,6 +92,7 @@ extern const char *lhd_get_substring_location (const substring_loc &,
                                               location_t *out_loc);
 extern int lhd_decl_dwarf_attribute (const_tree, int);
 extern int lhd_type_dwarf_attribute (const_tree, int);
+extern void lhd_finalize_early_debug (void);
 
 #define LANG_HOOKS_NAME                        "GNU unknown"
 #define LANG_HOOKS_IDENTIFIER_SIZE     sizeof (struct lang_identifier)
@@ -139,6 +140,7 @@ extern int lhd_type_dwarf_attribute (const_tree, int);
 #define LANG_HOOKS_EMITS_BEGIN_STMT    false
 #define LANG_HOOKS_RUN_LANG_SELFTESTS   lhd_do_nothing
 #define LANG_HOOKS_GET_SUBSTRING_LOCATION lhd_get_substring_location
+#define LANG_HOOKS_FINALIZE_EARLY_DEBUG lhd_finalize_early_debug
 
 /* Attribute hooks.  */
 #define LANG_HOOKS_ATTRIBUTE_TABLE             NULL
@@ -364,7 +366,8 @@ extern void lhd_end_section (void);
   LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS, \
   LANG_HOOKS_EMITS_BEGIN_STMT, \
   LANG_HOOKS_RUN_LANG_SELFTESTS, \
-  LANG_HOOKS_GET_SUBSTRING_LOCATION \
+  LANG_HOOKS_GET_SUBSTRING_LOCATION, \
+  LANG_HOOKS_FINALIZE_EARLY_DEBUG \
 }
 
 #endif /* GCC_LANG_HOOKS_DEF_H */

diff --git a/gcc/langhooks.c b/gcc/langhooks.c
index 1cb7cda5b79309491bd89d3752a9a5b2a445120f..3cbe04c6899ae72468c4a89c2391a15e0b83c8fe 100644 (file)
--- a/gcc/langhooks.c
+++ b/gcc/langhooks.c
@@ -36,6 +36,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "output.h"
 #include "timevar.h"
 #include "stor-layout.h"
+#include "cgraph.h"
+#include "debug.h"
 
 /* Do nothing; in many cases the default hook.  */
 
@@ -866,6 +868,18 @@ lhd_unit_size_without_reusable_padding (tree t)
   return TYPE_SIZE_UNIT (t);
 }
 
+/* Default implementation for the finalize_early_debug hook.  */
+
+void
+lhd_finalize_early_debug (void)
+{
+  /* Emit early debug for reachable functions, and by consequence,
+     locally scoped symbols.  */
+  struct cgraph_node *cnode;
+  FOR_EACH_FUNCTION_WITH_GIMPLE_BODY (cnode)
+    (*debug_hooks->early_global_decl) (cnode->decl);
+}
+
 /* Returns true if the current lang_hooks represents the GNU C frontend.  */
 
 bool

diff --git a/gcc/langhooks.h b/gcc/langhooks.h
index 2bd5a67cd3703ecc4affa9cd9fcdc2cc622a3315..6ab6fb682f3bf63d63ac48d8b0de3a5a2242dae5 100644 (file)
--- a/gcc/langhooks.h
+++ b/gcc/langhooks.h
@@ -580,6 +580,9 @@ struct lang_hooks
   const char *(*get_substring_location) (const substring_loc &,
                                         location_t *out_loc);
 
+  /* Invoked before the early_finish debug hook is invoked.  */
+  void (*finalize_early_debug) (void);
+
   /* Whenever you add entries here, make sure you adjust langhooks-def.h
      and langhooks.c accordingly.  */
 };

diff --git a/gcc/testsuite/gcc.dg/debug/dwarf2/pr96383-1.c b/gcc/testsuite/gcc.dg/debug/dwarf2/pr96383-1.c
new file mode 100644 (file)
index 0000000..a9c0efb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/dwarf2/pr96383-1.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-g -gdwarf -dA" } */
+
+extern void foo (int);
+extern void unusedbar (int);
+
+int main()
+{
+  foo (1);
+}
+
+/* We want subprogram DIEs for both foo and main and a DIE for
+   the formal parameter of foo.  We do not want a DIE for
+   unusedbar.  */
+/* { dg-final { scan-assembler-times "DW_TAG_subprogram" 4 } } */
+/* { dg-final { scan-assembler-times "DW_TAG_formal_parameter" 2 } } */
+/* { dg-final { scan-assembler-not "unusedbar" } } */

diff --git a/gcc/testsuite/gcc.dg/debug/dwarf2/pr96383-2.c b/gcc/testsuite/gcc.dg/debug/dwarf2/pr96383-2.c
new file mode 100644 (file)
index 0000000..c3a710e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/dwarf2/pr96383-2.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-g -O2 -gdwarf -dA" } */
+
+extern void foo (int);
+extern void unusedbar (int);
+
+int main()
+{
+  foo (1);
+}
+
+/* We want subprogram DIEs for both foo and main and a DIE for
+   the formal parameter of foo.  We do not want a DIE for
+   unusedbar.  */
+/* { dg-final { scan-assembler-times "DW_TAG_subprogram" 4 } } */
+/* { dg-final { scan-assembler-times "DW_TAG_formal_parameter" 2 } } */
+/* { dg-final { scan-assembler-not "unusedbar" } } */

diff --git a/libstdc++-v3/testsuite/20_util/assume_aligned/3.cc b/libstdc++-v3/testsuite/20_util/assume_aligned/3.cc
index d1435b54014f46e6f512507af22d92f28331c192..25f64d7aad144499cc6891bf5102f677e5c68a26 100644 (file)
--- a/libstdc++-v3/testsuite/20_util/assume_aligned/3.cc
+++ b/libstdc++-v3/testsuite/20_util/assume_aligned/3.cc
@@ -15,7 +15,7 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-// { dg-options "-std=gnu++2a -O2" }
+// { dg-options "-std=gnu++2a -O2 -g0" }
 // { dg-do compile { target c++2a } }
 // { dg-final { scan-assembler-not "undefined" } }