[PATCH 1/2] Remove casts from dwarf2/index-write.c

[PATCH 1/2] Remove casts from dwarf2/index-write.c

[Tom Tromey]

dwarf2/index-write.c casts pointers to "dwarf2_psymtab *", but as far
as I can tell, it does not actually use any DWARF-specific fields of
the psymtab.  So, this patch changes this code to use partial_symtab
instead.  This removes nearly every cast, leaving just the unavoidable
one from addrmap iteration.

gdb/ChangeLog
2020-02-25  Tom Tromey  <tom@tromey.com>

	* dwarf2/index-write.c (psym_index_map): Change type.
	(add_address_entry_worker, write_one_signatured_type)
	(recursively_count_psymbols, recursively_write_psymbols)
	(class debug_names, psyms_seen_size, write_gdbindex)
	(write_debug_names): Use partial_symtab, not dwarf2_psymtab.
---
 gdb/ChangeLog            |  8 ++++++++
 gdb/dwarf2/index-write.c | 26 +++++++++++++-------------
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/gdb/dwarf2/index-write.c b/gdb/dwarf2/index-write.c
index 2cbf2ebd202..4b711d0d29a 100644
--- a/gdb/dwarf2/index-write.c
+++ b/gdb/dwarf2/index-write.c
@@ -399,7 +399,7 @@ write_hash_table (mapped_symtab *symtab, data_buf &output, data_buf &cpool)
     }
 }
 
-typedef std::unordered_map<dwarf2_psymtab *, unsigned int> psym_index_map;
+typedef std::unordered_map<partial_symtab *, unsigned int> psym_index_map;
 
 /* Helper struct for building the address table.  */
 struct addrmap_index_data
@@ -439,7 +439,7 @@ static int
 add_address_entry_worker (void *datap, CORE_ADDR start_addr, void *obj)
 {
   struct addrmap_index_data *data = (struct addrmap_index_data *) datap;
-  dwarf2_psymtab *pst = (dwarf2_psymtab *) obj;
+  partial_symtab *pst = (partial_symtab *) obj;
 
   if (data->previous_valid)
     add_address_entry (data->objfile, data->addr_vec,
@@ -582,7 +582,7 @@ write_one_signatured_type (void **slot, void *d)
   struct signatured_type_index_data *info
     = (struct signatured_type_index_data *) d;
   struct signatured_type *entry = (struct signatured_type *) *slot;
-  dwarf2_psymtab *psymtab = entry->per_cu.v.psymtab;
+  partial_symtab *psymtab = entry->per_cu.v.psymtab;
 
   write_psymbols (info->symtab,
 		  info->psyms_seen,
@@ -612,12 +612,12 @@ write_one_signatured_type (void **slot, void *d)
    if they appeared in this psymtab.  */
 
 static void
-recursively_count_psymbols (dwarf2_psymtab *psymtab,
+recursively_count_psymbols (partial_symtab *psymtab,
 			    size_t &psyms_seen)
 {
   for (int i = 0; i < psymtab->number_of_dependencies; ++i)
     if (psymtab->dependencies[i]->user != NULL)
-      recursively_count_psymbols ((dwarf2_psymtab *) psymtab->dependencies[i],
+      recursively_count_psymbols (psymtab->dependencies[i],
 				  psyms_seen);
 
   psyms_seen += psymtab->n_global_syms;
@@ -629,7 +629,7 @@ recursively_count_psymbols (dwarf2_psymtab *psymtab,
 
 static void
 recursively_write_psymbols (struct objfile *objfile,
-			    dwarf2_psymtab *psymtab,
+			    partial_symtab *psymtab,
 			    struct mapped_symtab *symtab,
 			    std::unordered_set<partial_symbol *> &psyms_seen,
 			    offset_type cu_index)
@@ -639,7 +639,7 @@ recursively_write_psymbols (struct objfile *objfile,
   for (i = 0; i < psymtab->number_of_dependencies; ++i)
     if (psymtab->dependencies[i]->user != NULL)
       recursively_write_psymbols (objfile,
-				  (dwarf2_psymtab *) psymtab->dependencies[i],
+				  psymtab->dependencies[i],
 				  symtab, psyms_seen, cu_index);
 
   write_psymbols (symtab,
@@ -869,14 +869,14 @@ public:
      as if they appeared in this psymtab.  */
   void recursively_write_psymbols
     (struct objfile *objfile,
-     dwarf2_psymtab *psymtab,
+     partial_symtab *psymtab,
      std::unordered_set<partial_symbol *> &psyms_seen,
      int cu_index)
   {
     for (int i = 0; i < psymtab->number_of_dependencies; ++i)
       if (psymtab->dependencies[i]->user != NULL)
 	recursively_write_psymbols
-	  (objfile, (dwarf2_psymtab *) psymtab->dependencies[i], psyms_seen, cu_index);
+	  (objfile, psymtab->dependencies[i], psyms_seen, cu_index);
 
     write_psymbols (psyms_seen,
 		    (objfile->partial_symtabs->global_psymbols.data ()
@@ -1234,7 +1234,7 @@ private:
   write_one_signatured_type (struct signatured_type *entry,
 			     struct signatured_type_index_data *info)
   {
-    dwarf2_psymtab *psymtab = entry->per_cu.v.psymtab;
+    partial_symtab *psymtab = entry->per_cu.v.psymtab;
 
     write_psymbols (info->psyms_seen,
 		    (info->objfile->partial_symtabs->global_psymbols.data ()
@@ -1320,7 +1320,7 @@ psyms_seen_size (struct dwarf2_per_objfile *dwarf2_per_objfile)
   size_t psyms_count = 0;
   for (dwarf2_per_cu_data *per_cu : dwarf2_per_objfile->all_comp_units)
     {
-      dwarf2_psymtab *psymtab = per_cu->v.psymtab;
+      partial_symtab *psymtab = per_cu->v.psymtab;
 
       if (psymtab != NULL && psymtab->user == NULL)
 	recursively_count_psymbols (psymtab, psyms_count);
@@ -1423,7 +1423,7 @@ write_gdbindex (struct dwarf2_per_objfile *dwarf2_per_objfile, FILE *out_file,
     {
       struct dwarf2_per_cu_data *per_cu
 	= dwarf2_per_objfile->all_comp_units[i];
-      dwarf2_psymtab *psymtab = per_cu->v.psymtab;
+      partial_symtab *psymtab = per_cu->v.psymtab;
 
       /* CU of a shared file from 'dwz -m' may be unused by this main file.
 	 It may be referenced from a local scope but in such case it does not
@@ -1508,7 +1508,7 @@ write_debug_names (struct dwarf2_per_objfile *dwarf2_per_objfile,
   for (int i = 0; i < dwarf2_per_objfile->all_comp_units.size (); ++i)
     {
       const dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->all_comp_units[i];
-      dwarf2_psymtab *psymtab = per_cu->v.psymtab;
+      partial_symtab *psymtab = per_cu->v.psymtab;
 
       /* CU of a shared file from 'dwz -m' may be unused by this main
 	 file.  It may be referenced from a local scope but in such
-- 
2.17.2

[PATCH 2/2] Specialize partial_symtab for DWARF include files

[Tom Tromey]

Include files are represented by a partial symtab, but don't expand to
anything.  From dwarf2_psymtab::expand_psymtab:

  if (per_cu == NULL)
    {
      /* It's an include file, no symbols to read for it.
         Everything is in the parent symtab.  */
      readin = true;
      return;
    }

This patch introduces a new specialization of partial_symtab to handle
this case.  In addition to being slightly smaller, I believe an
include file is the only situation where a DWARF psymtab can result in
a null compunit_symtab.  This adds an assert to that effect as well.
This change will simplify one of the psymtab sharing patches.

gdb/ChangeLog
2020-02-25  Tom Tromey  <tom@tromey.com>

	* dwarf2/read.c (struct dwarf2_include_psymtab): New.
	(dwarf2_create_include_psymtab): Use dwarf2_include_psymtab.
	(dwarf2_psymtab::expand_psymtab, dwarf2_psymtab::readin_p)
	(dwarf2_psymtab::get_compunit_symtab): Remove null checks for
	per_cu_data.
---
 gdb/ChangeLog     |  8 +++++++
 gdb/dwarf2/read.c | 61 ++++++++++++++++++++++++++++++++---------------
 2 files changed, 50 insertions(+), 19 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 8c40ddb727a..d22a53deb25 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -5894,6 +5894,45 @@ read_abbrev_offset (struct dwarf2_per_objfile *dwarf2_per_objfile,
   return (sect_offset) read_offset (abfd, info_ptr, offset_size);
 }
 
+/* A partial symtab that is used only for include files.  */
+struct dwarf2_include_psymtab : public partial_symtab
+{
+  dwarf2_include_psymtab (const char *filename, struct objfile *objfile)
+    : partial_symtab (filename, objfile)
+  {
+  }
+
+  void read_symtab (struct objfile *objfile) override
+  {
+    expand_psymtab (objfile);
+  }
+
+  void expand_psymtab (struct objfile *objfile) override
+  {
+    if (m_readin)
+      return;
+    /* It's an include file, no symbols to read for it.
+       Everything is in the parent symtab.  */
+    read_dependencies (objfile);
+    m_readin = true;
+  }
+
+  bool readin_p () const override
+  {
+    return m_readin;
+  }
+
+  struct compunit_symtab *get_compunit_symtab () const
+    override
+  {
+    return nullptr;
+  }
+
+private:
+
+  bool m_readin = false;
+};
+
 /* Allocate a new partial symtab for file named NAME and mark this new
    partial symtab as being an include of PST.  */
 
@@ -5901,7 +5940,7 @@ static void
 dwarf2_create_include_psymtab (const char *name, dwarf2_psymtab *pst,
                                struct objfile *objfile)
 {
-  dwarf2_psymtab *subpst = new dwarf2_psymtab (name, objfile);
+  dwarf2_include_psymtab *subpst = new dwarf2_include_psymtab (name, objfile);
 
   if (!IS_ABSOLUTE_PATH (subpst->filename))
     {
@@ -5912,11 +5951,6 @@ dwarf2_create_include_psymtab (const char *name, dwarf2_psymtab *pst,
   subpst->dependencies = objfile->partial_symtabs->allocate_dependencies (1);
   subpst->dependencies[0] = pst;
   subpst->number_of_dependencies = 1;
-
-  /* No private part is necessary for include psymtabs.  This property
-     can be used to differentiate between such include psymtabs and
-     the regular ones.  */
-  subpst->per_cu_data = nullptr;
 }
 
 /* Read the Line Number Program data and extract the list of files
@@ -8827,24 +8861,13 @@ process_queue (struct dwarf2_per_objfile *dwarf2_per_objfile)
 void
 dwarf2_psymtab::expand_psymtab (struct objfile *objfile)
 {
-  struct dwarf2_per_cu_data *per_cu;
-
   if (readin)
     return;
 
   read_dependencies (objfile);
 
-  per_cu = per_cu_data;
-
-  if (per_cu == NULL)
-    {
-      /* It's an include file, no symbols to read for it.
-         Everything is in the parent symtab.  */
-      readin = true;
-      return;
-    }
-
-  dw2_do_instantiate_symtab (per_cu, false);
+  dw2_do_instantiate_symtab (per_cu_data, false);
+  gdb_assert (get_compunit_symtab () != nullptr);
 }
 
 /* Trivial hash function for die_info: the hash value of a DIE
-- 
2.17.2

[PATCH 0/2] Specialize partial_symtab for DWARF include files

[Tom Tromey]

This started as just a patch to Specialize partial_symtab for DWARF
include files, but then I noticed a bunch of casts in index-write.c
that would no longer be correct; and so it turned into a 2-patch
series.

This is the patch I was talking about in another thread.  I think it
will let us remove the optional<> from the psymtab sharing series.

Tested by the buildbot.

Tom

Re: [PATCH 1/2] Remove casts from dwarf2/index-write.c

[Simon Marchi]

On 2020-02-25 8:09 a.m., Tom Tromey wrote:
> dwarf2/index-write.c casts pointers to "dwarf2_psymtab *", but as far
> as I can tell, it does not actually use any DWARF-specific fields of
> the psymtab.  So, this patch changes this code to use partial_symtab
> instead.  This removes nearly every cast, leaving just the unavoidable
> one from addrmap iteration.

Thanks, that LGTM.

Simon

Re: [PATCH 2/2] Specialize partial_symtab for DWARF include files

[Simon Marchi]

On 2020-02-25 8:09 a.m., Tom Tromey wrote:
> Include files are represented by a partial symtab, but don't expand to
> anything.  From dwarf2_psymtab::expand_psymtab:
> 
>   if (per_cu == NULL)
>     {
>       /* It's an include file, no symbols to read for it.
>          Everything is in the parent symtab.  */
>       readin = true;
>       return;
>     }
> 
> This patch introduces a new specialization of partial_symtab to handle
> this case.  In addition to being slightly smaller, I believe an
> include file is the only situation where a DWARF psymtab can result in
> a null compunit_symtab.  This adds an assert to that effect as well.
> This change will simplify one of the psymtab sharing patches.
> 
> gdb/ChangeLog
> 2020-02-25  Tom Tromey  <tom@tromey.com>
> 
> 	* dwarf2/read.c (struct dwarf2_include_psymtab): New.
> 	(dwarf2_create_include_psymtab): Use dwarf2_include_psymtab.
> 	(dwarf2_psymtab::expand_psymtab, dwarf2_psymtab::readin_p)
> 	(dwarf2_psymtab::get_compunit_symtab): Remove null checks for
> 	per_cu_data.

Hi Tom,

From what I understand, this is fine, thanks.

> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index 8c40ddb727a..d22a53deb25 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -5894,6 +5894,45 @@ read_abbrev_offset (struct dwarf2_per_objfile *dwarf2_per_objfile,
>    return (sect_offset) read_offset (abfd, info_ptr, offset_size);
>  }
>  
> +/* A partial symtab that is used only for include files.  */
> +struct dwarf2_include_psymtab : public partial_symtab
> +{
> +  dwarf2_include_psymtab (const char *filename, struct objfile *objfile)
> +    : partial_symtab (filename, objfile)
> +  {
> +  }
> +
> +  void read_symtab (struct objfile *objfile) override
> +  {
> +    expand_psymtab (objfile);
> +  }
> +
> +  void expand_psymtab (struct objfile *objfile) override
> +  {
> +    if (m_readin)
> +      return;
> +    /* It's an include file, no symbols to read for it.
> +       Everything is in the parent symtab.  */
> +    read_dependencies (objfile);
> +    m_readin = true;
> +  }
> +
> +  bool readin_p () const override
> +  {
> +    return m_readin;
> +  }
> +
> +  struct compunit_symtab *get_compunit_symtab () const
> +    override

The override can be on the previous line.

Simon

Re: [PATCH 2/2] Specialize partial_symtab for DWARF include files

[Tom Tromey]

>> +  struct compunit_symtab *get_compunit_symtab () const
>> +    override

Simon> The override can be on the previous line.

Thanks.  I checked it in with that change.

Tom