[PATCH][PR28071]: Fix sched-deps.c to flush dependencies.

[Maxim Kuvyrkov]

Hi!

This is a patch for a problem described in 
http://gcc.gnu.org/ml/gcc-patches/2007-04/msg00760.html .

The problem is in sched-deps.c: flush_pending_lists () which 
*unconditionally* sets pending_lists_length to zero but flushes 
pending_read_* lists *conditionally*.  Such scenario happens when 
flushing on processing of a pure call which doesn't require 
pending_read_* to be flushed.

Adding separate counters for read_mems and write_mems instead of one 
cumulative pending_list_length counter will solve the problem.

PR28071: As a result of this patch the dependency analyzer now creates 
480K of dependencies instead of 3.5M it was used to.  Thus making the 
scheduler use ~7 time less memory on the testcase.

The patch is obvious and fixes a long standing issue which, IMHO, are 
good reasons for considering it for 4.2/4.1 branches as well.

Ok for trunk/4.2/4.1 ?


Thanks,

Maxim
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