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[6/8] Use std::unordered_map instead of htab_t.

Message ID 6182299f-ea49-9b68-8104-b797b40c0014@redhat.com
State New
Headers show

Commit Message

Keith Seitz Aug. 7, 2018, 2:57 p.m. UTC
On 07/11/2018 04:21 AM, Pedro Alves wrote:
> Yeah, it's not whether or not I _want_ you to revert.  Instead, data rules.

Ha ha. Indeed, it (data) does rule. I apologize for being so vague...

> I really have no awareness of whether that map ends up with a hundred entries
> or a hundred million entries, and thus whether the difference ends up
> significant.  So if after considering that you're not concerned, then
> neither am I.

I've revisited this topic a bit on the my C++ compile branch, and
there is sufficient evidence there to suggest that the type cache
could grow quite large -- especially for non-trivial compilations such
as compiling a file (or perhaps in the future if/when we support code
replacement or other advanced uses of this feature.

IIRC, I originally wrote this before the move to C++11 had been
proposed. Consequently unique_ptr was not available. Of course, it is
now, and it makes sense to me to move to using htab_up instead.

[The underlying storage for the error map doesn't really matter. That
map seldom has any entries in it.]

WDYT of the below patch?

Keith

Subject: [PATCH] Use unique_ptr for htabs

This patch updates the type-conversion caching in C compile to use
unique pointers.  This patch also removes the on-demand allocation of the
symbol error map in favor of initialization, simplifying the code.


gdb/ChangeLog
YYYY-MM-DD  Keith Seitz  <keiths@redhat.com>

	* compile/compile-internal.h (compile_instance::~compile_instance):
	Remove calls to htab_delete.
	<m_type_map, m_symbol_err_map>: Switch type to htab_up.
	* compile.c (compile_instance::compile_instance): Initialize
	htab unique pointers.
	(compile_instance::get_cached_type, compile_instance::insert_type)
	(compile_instance::error_symbol_once): Update for unique_ptr.
---
 gdb/compile/compile-internal.h |  7 ++-----
 gdb/compile/compile.c          | 28 ++++++++++------------------
 2 files changed, 12 insertions(+), 23 deletions(-)

Comments

Pedro Alves Aug. 8, 2018, 12:28 p.m. UTC | #1
On 08/07/2018 03:57 PM, Keith Seitz wrote:

> WDYT of the below patch?
> 
LGTM.

Thanks,
Pedro Alves
Keith Seitz Aug. 10, 2018, 6:18 p.m. UTC | #2
On 08/08/2018 05:28 AM, Pedro Alves wrote:
> On 08/07/2018 03:57 PM, Keith Seitz wrote:
> 
>> WDYT of the below patch?
>>
> LGTM.

And with that, I've pushed the entire series.

Thank you for reviewing and your advice!

Keith
diff mbox

Patch

diff --git a/gdb/compile/compile-internal.h b/gdb/compile/compile-internal.h
index 3916f84f6f..c8d2d2f427 100644
--- a/gdb/compile/compile-internal.h
+++ b/gdb/compile/compile-internal.h
@@ -49,9 +49,6 @@  public:
   virtual ~compile_instance ()
   {
     m_gcc_fe->ops->destroy (m_gcc_fe);
-    htab_delete (m_type_map);
-    if (m_symbol_err_map != NULL)
-      htab_delete (m_symbol_err_map);
   }
 
   /* Returns the GCC options to be passed during compilation.  */
@@ -148,10 +145,10 @@  protected:
   std::string m_gcc_target_options;
 
   /* Map from gdb types to gcc types.  */
-  htab_t m_type_map;
+  htab_up m_type_map;
 
   /* Map from gdb symbols to gcc error messages to emit.  */
-  htab_t m_symbol_err_map;
+  htab_up m_symbol_err_map;
 };
 
 /* Define header and footers for different scopes.  */
diff --git a/gdb/compile/compile.c b/gdb/compile/compile.c
index 308c82ee54..31ae5970b9 100644
--- a/gdb/compile/compile.c
+++ b/gdb/compile/compile.c
@@ -129,11 +129,13 @@  del_symbol_error (void *a)
 compile_instance::compile_instance (struct gcc_base_context *gcc_fe,
 				    const char *options)
   : m_gcc_fe (gcc_fe), m_gcc_target_options (options),
-    m_symbol_err_map (NULL)
+    m_type_map (htab_create_alloc (10, hash_type_map_instance,
+				   eq_type_map_instance,
+				   xfree, xcalloc, xfree)),
+    m_symbol_err_map (htab_create_alloc (10, hash_symbol_error,
+					 eq_symbol_error, del_symbol_error,
+					 xcalloc, xfree))
 {
-  m_type_map = htab_create_alloc (10, hash_type_map_instance,
-				  eq_type_map_instance,
-				  xfree, xcalloc, xfree);
 }
 
 /* See compile-internal.h.  */
@@ -144,7 +146,7 @@  compile_instance::get_cached_type (struct type *type, gcc_type &ret) const
   struct type_map_instance inst, *found;
 
   inst.type = type;
-  found = (struct type_map_instance *) htab_find (m_type_map, &inst);
+  found = (struct type_map_instance *) htab_find (m_type_map.get (), &inst);
   if (found != NULL)
     {
       ret = found->gcc_type_handle;
@@ -164,7 +166,7 @@  compile_instance::insert_type (struct type *type, gcc_type gcc_type)
 
   inst.type = type;
   inst.gcc_type_handle = gcc_type;
-  slot = htab_find_slot (m_type_map, &inst, INSERT);
+  slot = htab_find_slot (m_type_map.get (), &inst, INSERT);
 
   add = (struct type_map_instance *) *slot;
   /* The type might have already been inserted in order to handle
@@ -189,18 +191,8 @@  compile_instance::insert_symbol_error (const struct symbol *sym,
   struct symbol_error e;
   void **slot;
 
-  if (m_symbol_err_map == NULL)
-    {
-      m_symbol_err_map = htab_create_alloc (10,
-					    hash_symbol_error,
-					    eq_symbol_error,
-					    del_symbol_error,
-					    xcalloc,
-					    xfree);
-    }
-
   e.sym = sym;
-  slot = htab_find_slot (m_symbol_err_map, &e, INSERT);
+  slot = htab_find_slot (m_symbol_err_map.get (), &e, INSERT);
   if (*slot == NULL)
     {
       struct symbol_error *e = XNEW (struct symbol_error);
@@ -223,7 +215,7 @@  compile_instance::error_symbol_once (const struct symbol *sym)
     return;
 
   search.sym = sym;
-  err = (struct symbol_error *) htab_find (m_symbol_err_map, &search);
+  err = (struct symbol_error *) htab_find (m_symbol_err_map.get (), &search);
   if (err == NULL || err->message == NULL)
     return;