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ira.c: Add comment about threads at the top of file. 

2013-11-13  Vladimir Makarov  <vmakarov@redhat.com>

	* ira.c: Add comment about threads at the top of file.

From-SVN: r204772
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Vladimir Makarov 2013-11-14 01:51:07 +00:00 committed by Vladimir Makarov
parent fffb16d263
commit 41808d153a
2 changed files with 12 additions and 1 deletions
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@ -1,3 +1,7 @@
2013-11-13 Vladimir Makarov <vmakarov@redhat.com>
* ira.c: Add comment about threads at the top of file.
2013-11-13 Vladimir Makarov <vmakarov@redhat.com>
* ira-color.c (coalesce_allocnos): Don't allocate and free

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gcc/ira.c
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@ -192,7 +192,14 @@ along with GCC; see the file COPYING3. If not see
this point. There is some freedom in the order of putting
allocnos on the stack which can affect the final result of
the allocation. IRA uses some heuristics to improve the
order.
order. The major one is to form *threads* from colorable
allocnos and push them on the stack by threads. Thread is a
set of non-conflicting colorable allocnos connected by
copies. The thread contains allocnos from the colorable
bucket or colorable allocnos already pushed onto the coloring
stack. Pushing thread allocnos one after another onto the
stack increases chances of removing copies when the allocnos
get the same hard reg.
We also use a modification of Chaitin-Briggs algorithm which
works for intersected register classes of allocnos. To