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* [Bug tree-optimization/61171] New: vectorization fails for a reduction in presence of subtraction
@ 2014-05-13 12:55 vincenzo.innocente at cern dot ch
2015-04-29 12:10 ` [Bug tree-optimization/61171] " rguenth at gcc dot gnu.org
2015-06-17 11:48 ` alalaw01 at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: vincenzo.innocente at cern dot ch @ 2014-05-13 12:55 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171
Bug ID: 61171
Summary: vectorization fails for a reduction in presence of
subtraction
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vincenzo.innocente at cern dot ch
give this code
cat bug.cc
float px[1024];
float xx, vv;
unsigned int N=1024;
void ok() {
for (auto j=0U; j<N; ++j) {
auto ax = px[j]-xx;
vv-=ax;
}
}
void noOk() {
for (auto j=0U; j<N; ++j) {
auto ax = xx-px[j];
vv+=ax;
}
}
c++ -std=c++11 -Ofast -S bug.cc -march=haswell -fopt-info-vec-missed; cat
bug.s
ok vectorize, noOk does not because
bug.cc:13:3: note: reduction: not commutative/associative: vv.6_9 = _2 - _6;
even if the code is clearly identical (at least with Ofast)
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/61171] vectorization fails for a reduction in presence of subtraction
2014-05-13 12:55 [Bug tree-optimization/61171] New: vectorization fails for a reduction in presence of subtraction vincenzo.innocente at cern dot ch
@ 2015-04-29 12:10 ` rguenth at gcc dot gnu.org
2015-06-17 11:48 ` alalaw01 at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu.org @ 2015-04-29 12:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2015-04-29
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/61171] vectorization fails for a reduction in presence of subtraction
2014-05-13 12:55 [Bug tree-optimization/61171] New: vectorization fails for a reduction in presence of subtraction vincenzo.innocente at cern dot ch
2015-04-29 12:10 ` [Bug tree-optimization/61171] " rguenth at gcc dot gnu.org
@ 2015-06-17 11:48 ` alalaw01 at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: alalaw01 at gcc dot gnu.org @ 2015-06-17 11:48 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171
alalaw01 at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |alalaw01 at gcc dot gnu.org
--- Comment #2 from alalaw01 at gcc dot gnu.org ---
This vectorizes fine, if vv is made a local variable:
float isOk() {
float vv = 0;
for (int j=0U; j<N; ++j) {
float ax = xx-px[j];
vv+=ax;
}
return vv;
}
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2015-06-17 11:48 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2014-05-13 12:55 [Bug tree-optimization/61171] New: vectorization fails for a reduction in presence of subtraction vincenzo.innocente at cern dot ch
2015-04-29 12:10 ` [Bug tree-optimization/61171] " rguenth at gcc dot gnu.org
2015-06-17 11:48 ` alalaw01 at gcc dot gnu.org
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