ping: [gcc patch] DWARF-5: Define DW_IDX_GNU_static and DW_IDX_GNU_external
diff mbox

Message ID 20170623085813.GA19725@host1.jankratochvil.net
State New
Headers show

Commit Message

Jan Kratochvil June 23, 2017, 8:58 a.m. UTC
http://dwarfstd.org/ShowIssue.php?issue=170527.1

170527.1 Jan Kratochvil DW_IDX_* for static/extern symbols Enhancement Open 

Section 6.1.1.4.7, pg 147
When a debugger wants to print 'somename' it logically tries to find first 'somename' as an 
external symbol in all available libraries.  Only if none such external symbol is found the 
debugger starts searching for a static 'somename' symbol in those libraries.

This requires to know whether a symbol in .debug_names index has DW_AT_external or not.  
Otherwise a lot of needless CU expansions happen.  This extension improves performance 
gain of the .debug_names index.

(Discovered in an original fix by Doug Evans - GDB Bug 14125.)

Proposing and asking for pre-allocation:
  DW_IDX_static   = 6 = DW_FORM_flag_present = DIE's DW_AT_external is not present
  DW_IDX_external = 7 = DW_FORM_flag_present = DIE's DW_AT_external is present
include/ChangeLog
2017-05-26  Jan Kratochvil  <jan.kratochvil@redhat.com>

        * dwarf2.def (DW_IDX_compile_unit, DW_IDX_type_unit, DW_IDX_die_offset)
        (DW_IDX_parent, DW_IDX_type_hash, DW_IDX_lo_user, DW_IDX_hi_user)
        (DW_IDX_GNU_static, DW_IDX_GNU_external): New.
        * dwarf2.h (DW_IDX, DW_IDX_DUP, DW_FIRST_IDX, DW_END_IDX): New.
        (enum dwarf_name_index_attribute): Remove.
        (get_DW_IDX_name): New declaration.

libiberty/ChangeLog
2017-05-26  Jan Kratochvil  <jan.kratochvil@redhat.com>

        * dwarfnames.c (DW_FIRST_IDX, DW_END_IDX, DW_IDX, DW_IDX_DUP): New.

Comments

Jan Kratochvil July 2, 2017, 7:25 a.m. UTC | #1
http://dwarfstd.org/ShowIssue.php?issue=170527.1

170527.1 Jan Kratochvil DW_IDX_* for static/extern symbols Enhancement Open 

Section 6.1.1.4.7, pg 147
When a debugger wants to print 'somename' it logically tries to find first 'somename' as an 
external symbol in all available libraries.  Only if none such external symbol is found the 
debugger starts searching for a static 'somename' symbol in those libraries.

This requires to know whether a symbol in .debug_names index has DW_AT_external or not.  
Otherwise a lot of needless CU expansions happen.  This extension improves performance 
gain of the .debug_names index.

(Discovered in an original fix by Doug Evans - GDB Bug 14125.)

Proposing and asking for pre-allocation:
  DW_IDX_static   = 6 = DW_FORM_flag_present = DIE's DW_AT_external is not present
  DW_IDX_external = 7 = DW_FORM_flag_present = DIE's DW_AT_external is present
Jason Merrill July 2, 2017, 4:22 p.m. UTC | #2
On Sun, Jul 2, 2017 at 3:25 AM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> http://dwarfstd.org/ShowIssue.php?issue=170527.1
>
> 170527.1 Jan Kratochvil DW_IDX_* for static/extern symbols Enhancement Open
>
> Section 6.1.1.4.7, pg 147
> When a debugger wants to print 'somename' it logically tries to find first 'somename' as an
> external symbol in all available libraries.  Only if none such external symbol is found the
> debugger starts searching for a static 'somename' symbol in those libraries.
>
> This requires to know whether a symbol in .debug_names index has DW_AT_external or not.
> Otherwise a lot of needless CU expansions happen.  This extension improves performance
> gain of the .debug_names index.
>
> (Discovered in an original fix by Doug Evans - GDB Bug 14125.)
>
> Proposing and asking for pre-allocation:
>   DW_IDX_static   = 6 = DW_FORM_flag_present = DIE's DW_AT_external is not present
>   DW_IDX_external = 7 = DW_FORM_flag_present = DIE's DW_AT_external is present

I'd suggest "internal" rather than "static".  Otherwise the patch looks good.

Jason
Jan Kratochvil July 2, 2017, 8:01 p.m. UTC | #3
On Sun, 02 Jul 2017 18:22:45 +0200, Jason Merrill wrote:
> I'd suggest "internal" rather than "static".  Otherwise the patch looks good.

Checked in as r249883 with: DW_IDX_GNU_internal, DW_IDX_GNU_external


Jan

Patch
diff mbox

diff --git a/include/dwarf2.def b/include/dwarf2.def
index ea6194e..1f0d50f 100644
--- a/include/dwarf2.def
+++ b/include/dwarf2.def
@@ -782,3 +782,15 @@  DW_CFA (DW_CFA_GNU_args_size, 0x2e)
 DW_CFA (DW_CFA_GNU_negative_offset_extended, 0x2f)
 
 DW_END_CFA
+
+/* Index attributes in the Abbreviations Table.  */
+DW_FIRST_IDX (DW_IDX_compile_unit, 1)
+DW_IDX (DW_IDX_type_unit, 2)
+DW_IDX (DW_IDX_die_offset, 3)
+DW_IDX (DW_IDX_parent, 4)
+DW_IDX (DW_IDX_type_hash, 5)
+DW_IDX_DUP (DW_IDX_lo_user, 0x2000)
+DW_IDX (DW_IDX_hi_user, 0x3fff)
+DW_IDX (DW_IDX_GNU_static, 0x2000)
+DW_IDX (DW_IDX_GNU_external, 0x2001)
+DW_END_IDX
diff --git a/include/dwarf2.h b/include/dwarf2.h
index 9c78880..14b6f22 100644
--- a/include/dwarf2.h
+++ b/include/dwarf2.h
@@ -52,6 +52,8 @@ 
 #define DW_ATE(name, value) , name = value
 #define DW_ATE_DUP(name, value) , name = value
 #define DW_CFA(name, value) , name = value
+#define DW_IDX(name, value) , name = value
+#define DW_IDX_DUP(name, value) , name = value
 
 #define DW_FIRST_TAG(name, value) enum dwarf_tag { \
   name = value
@@ -71,6 +73,9 @@ 
 #define DW_FIRST_CFA(name, value) enum dwarf_call_frame_info { \
   name = value
 #define DW_END_CFA };
+#define DW_FIRST_IDX(name, value) enum dwarf_name_index_attribute { \
+  name = value
+#define DW_END_IDX };
 
 #include "dwarf2.def"
 
@@ -86,6 +91,8 @@ 
 #undef DW_END_ATE
 #undef DW_FIRST_CFA
 #undef DW_END_CFA
+#undef DW_FIRST_IDX
+#undef DW_END_IDX
 
 #undef DW_TAG
 #undef DW_TAG_DUP
@@ -97,6 +104,8 @@ 
 #undef DW_ATE
 #undef DW_ATE_DUP
 #undef DW_CFA
+#undef DW_IDX
+#undef DW_IDX_DUP
 
 /* Flag that tells whether entry has a child or not.  */
 #define DW_children_no   0
@@ -420,18 +429,6 @@  enum dwarf_macro_record_type
     DW_MACRO_GNU_hi_user = 0xff
   };
 
-/* Index attributes in the Abbreviations Table.  */
-enum dwarf_name_index_attribute
-  {
-    DW_IDX_compile_unit = 1,
-    DW_IDX_type_unit = 2,
-    DW_IDX_die_offset = 3,
-    DW_IDX_parent = 4,
-    DW_IDX_type_hash = 5,
-    DW_IDX_lo_user = 0x2000,
-    DW_IDX_hi_user = 0x3fff
-  };
-
 /* Range list entry kinds in .debug_rnglists* section.  */
 enum dwarf_range_list_entry
   {
@@ -524,6 +521,10 @@  extern const char *get_DW_ATE_name (unsigned int enc);
    recognized.  */
 extern const char *get_DW_CFA_name (unsigned int opc);
 
+/* Return the name of a DW_IDX_ constant, or NULL if the value is not
+   recognized.  */
+extern const char *get_DW_IDX_name (unsigned int idx);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
diff --git a/libiberty/dwarfnames.c b/libiberty/dwarfnames.c
index 62563b7..e58d03c 100644
--- a/libiberty/dwarfnames.c
+++ b/libiberty/dwarfnames.c
@@ -59,6 +59,11 @@  Boston, MA 02110-1301, USA.  */
   switch (opc) {					\
   DW_CFA (name, value)
 #define DW_END_CFA } return 0; }
+#define DW_FIRST_IDX(name, value) \
+  const char *get_DW_IDX_name (unsigned int idx) {	\
+  switch (idx) {					\
+  DW_IDX (name, value)
+#define DW_END_IDX } return 0; }
 
 #define DW_TAG(name, value) case name: return # name ;
 #define DW_TAG_DUP(name, value)
@@ -70,6 +75,8 @@  Boston, MA 02110-1301, USA.  */
 #define DW_ATE(name, value) case name: return # name ;
 #define DW_ATE_DUP(name, value)
 #define DW_CFA(name, value) case name: return # name ;
+#define DW_IDX(name, value) case name: return # name ;
+#define DW_IDX_DUP(name, value)
 
 #include "dwarf2.def"
 
@@ -85,6 +92,8 @@  Boston, MA 02110-1301, USA.  */
 #undef DW_END_ATE
 #undef DW_FIRST_CFA
 #undef DW_END_CFA
+#undef DW_FIRST_IDX
+#undef DW_END_IDX
 
 #undef DW_TAG
 #undef DW_TAG_DUP
@@ -96,3 +105,5 @@  Boston, MA 02110-1301, USA.  */
 #undef DW_ATE
 #undef DW_ATE_DUP
 #undef DW_CFA
+#undef DW_IDX
+#undef DW_IDX_DUP