The following patch solves PR49865. The problem is described on
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49865
The patch changes code a bit only for gcc, crafty, and mesa on x86.
There is no visible change in the performance.
Only code for crafty is changed on x86-64 and improvement in the
performance is about 0.3%.
The patch was successfully bootstrapped on x86/x86-64.
The patch has been committed as rev. 182553.
2011-12-20 Vladimir Makarov <vmaka...@redhat.com>
PR target/49865
* ira-costs.c (find_costs_and_classes): Prefer registers even
if the memory cost is the same.
Index: ira-costs.c
===================================================================
--- ira-costs.c (revision 182552)
+++ ira-costs.c (working copy)
@@ -1693,7 +1693,14 @@ find_costs_and_classes (FILE *dump_file)
else if (i_costs[k] == best_cost)
best = ira_reg_class_subunion[best][rclass];
if (pass == flag_expensive_optimizations
- && i_costs[k] < i_mem_cost
+ /* We still prefer registers to memory even at this
+ stage if their costs are the same. We will make
+ a final decision during assigning hard registers
+ when we have all info including more accurate
+ costs which might be affected by assigning hard
+ registers to other pseudos because the pseudos
+ involved in moves can be coalesced. */
+ && i_costs[k] <= i_mem_cost
&& (reg_class_size[reg_class_subunion[alt_class][rclass]]
> reg_class_size[alt_class]))
alt_class = reg_class_subunion[alt_class][rclass];
