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[Bug tree-optimization/61619] Benefits from -ftree-vectorize lost easily when changing unrelated code
- From: "rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Thu, 26 Jun 2014 14:29:14 +0000
- Subject: [Bug tree-optimization/61619] Benefits from -ftree-vectorize lost easily when changing unrelated code
- Auto-submitted: auto-generated
- References: <bug-61619-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61619
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2014-06-26
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
bug.cpp:69:13: note: not vectorized: number of iterations cannot be computed.
bug.cpp:69:13: note: bad loop form.
The loop is
<bb 20>:
# sum_62 = PHI <sum_42(19), [bug.cpp : 69:80] sum_33(21)>
# p_71 = PHI <p_59(19), [bug.cpp : 29:29] p_50(21)>
[bug.cpp : 69:80] _32 = [bug.cpp : 69] *p_71;
[bug.cpp : 69:80] sum_33 = sum_62 + _32;
[bug.cpp : 29:31] p_50 = p_71 + pretmp_7;
[bug.cpp : 69:13] if (_48 != p_50)
goto <bb 21>;
else
goto <bb 22>;
<bb 21>:
goto <bb 20>;
The above is with -fopt-info-vec-missed and the excerpt is from the
bug.cpp.114t.vect file produced by -fdump-tree-vect-details-lineno
I believe the issue is that the initialization of S and E are not
inlined if none of the uncomments are done. If you expect all
abstraction to be removed by inlining the 'flatten' attribute can do magic.
Unfortunately the inits look like
[/usr/include/c++/4.9/bits/stl_algobase.h : 378:6] MEM[(char * {ref-all})&S]
= MEM[(char * {ref-all})&._94];
pretmp_22 = MEM[(struct array *)&S];
which we don't fold to the constant init 1 for some reason.