[partial backport from gcc-4.8/trunk r188667 <mikpe@it.uu.se>]

Date: Tue, 29 May 2012 13:59:24 +0200 (CEST)
From: Michael Matz <matz at suse dot de>
Subject: Re: RFA: Speedup expand_used_vars by 30 times (PR38474)
List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>

Hi,

On Tue, 29 May 2012, Richard Guenther wrote:

> > The other change in function.c further improves the temp slot 
> > machinery. While expanding free_temp_slots is called after each 
> > statement, and if it is able to free a slot it needs to update the 
> > RTX->slot mapping (a htab_t).  The freeing of slots was done 
> > incorrectly, it overwrote the slot in question with NULL, but it 
> > should have used htab_clear_slot.
> 
> That looks like a bugfix applicable to branches?

Perhaps, though the results of this bug are only worse code generation.  
When the chains are broken due to the bug some RTX->slot mappings aren't 
found anymore, but the code deals conservatively with that.

gcc/

2012-06-15  Michael Matz  <matz@suse.de>

	PR middle-end/38474
	* function.c (remove_unused_temp_slot_addresses_1): Use htab_clear_slot.

--- gcc-4.7.1/gcc/function.c.~1~	2012-05-12 23:37:23.000000000 +0200
+++ gcc-4.7.1/gcc/function.c	2012-06-24 13:06:05.000000000 +0200
@@ -709,7 +709,7 @@ remove_unused_temp_slot_addresses_1 (voi
   const struct temp_slot_address_entry *t;
   t = (const struct temp_slot_address_entry *) *slot;
   if (! t->temp_slot->in_use)
-    *slot = NULL;
+    htab_clear_slot (temp_slot_address_table, slot);
   return 1;
 }