https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63155
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2014-09-03
Target Milestone|--- |4.9.2
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Clearly caused by the correctness fix for setjmp to wire abnormal edges.
For me it is out-of-ssa which uses too much memory while building
the conflict graph.
We have gigantic PHI nodes here:
_10263(ab) = PHI <_109925(D)(ab)(2),...., _10592(ab)(1489)>
it's fast when optimizing.
At -O0 we have a _lot_ more anonymous SSA names.
-O1:
<bb 4>:
# _1(ab) = PHI <_1902(3), _2(ab)(5)>
_1905 = _setjmp (_1(ab));
if (_1905 == 0)
goto <bb 6>;
else
goto <bb 8>;
<bb 5>
# _2(ab) = PHI <_1895(D), .... single gigantic PHI
-O0:
<bb 4>:
# _1(ab) = PHI <_398164(3), _2(ab)(5)>
# _632(ab) = PHI <_397532(D)(ab)(3), _633(ab)(5)>
# _1263(ab) = PHI <_397533(D)(ab)(3), _1264(ab)(5)>
# _1894(ab) = PHI <_397534(D)(ab)(3), _1895(ab)(5)>
# _2525(ab) = PHI <_397535(D)(ab)(3), _2526(ab)(5)>
...
# _396900(ab) = PHI <_398160(D)(ab)(3), _396901(ab)(5)>
_398165 = _setjmp (_1(ab));
if (_398165 == 0)
goto <bb 6>;
else
goto <bb 8>;
<bb 5>
# _2(ab) = PHI <_397531(D)(ab)(2)...
....
# _396901(ab) = PHI <_398160(D)(ab)(2), _3...
gazillion of gigantic PHIs. And very many PHIs in every block.
It's into-SSA that introduces the difference for the PHI nodes
but already GIMPLIFICATION that introduces very many more
temporaries which is the underlying issue (lookup_tmp_var
!optimize check).
Index: gcc/gimplify.c
===================================================================
--- gcc/gimplify.c (revision 214810)
+++ gcc/gimplify.c (working copy)
@@ -476,7 +476,7 @@ lookup_tmp_var (tree val, bool is_formal
block, which means it will go into memory, causing much extra
work in reload and final and poorer code generation, outweighing
the extra memory allocation here. */
- if (!optimize || !is_formal || TREE_SIDE_EFFECTS (val))
+ if (!is_formal || TREE_SIDE_EFFECTS (val))
ret = create_tmp_from_val (val);
else
{
fixes it (but it means that changing the testcase to use more distinct
user variables would produce the same issue even when optimizing).
