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* [Bug tree-optimization/56625] New: After if-conversion vectorizer doesn't recognize similar stores
@ 2013-03-15 12:18 michael.v.zolotukhin at gmail dot com
2013-03-15 12:27 ` [Bug tree-optimization/56625] " rguenth at gcc dot gnu.org
2013-03-15 12:30 ` [Bug tree-optimization/56625] After if-conversion vectorizer doesn't recognize similar loads rguenth at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: michael.v.zolotukhin at gmail dot com @ 2013-03-15 12:18 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56625
Bug #: 56625
Summary: After if-conversion vectorizer doesn't recognize
similar stores
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: michael.v.zolotukhin@gmail.com
CC: kirill.yukhin@intel.com,
michael.v.zolotukhin@gmail.com
Build: 4.8.0 20130313
Created attachment 29673
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29673
Reproducer
In the following example there are two stores a[i]<-b[i] after if-conversion.
void foo (double a[], double b[])
{
int i;
for (i = 0; i < 100; i++)
{
if (a[i] == 0)
a[i] = b[i]*4;
else
a[i] = b[i]*3;
}
}
As vectorizer knows nothing about dependencies between a and b, it needs a
runtime test for it. But in the given example, vectorizer generates two
runtime-tests instead of one:
note: mark for run-time aliasing test between *_11 and *_8
note: mark for run-time aliasing test between *_15 and *_8
The test is attached, command line to reproduce:
gcc if-conv-runtime-tests.c -O3 -c -ftree-vectorizer-verbose=15
-ftree-loop-if-convert-stores -fdump-tree-vect
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/56625] After if-conversion vectorizer doesn't recognize similar stores
2013-03-15 12:18 [Bug tree-optimization/56625] New: After if-conversion vectorizer doesn't recognize similar stores michael.v.zolotukhin at gmail dot com
@ 2013-03-15 12:27 ` rguenth at gcc dot gnu.org
2013-03-15 12:30 ` [Bug tree-optimization/56625] After if-conversion vectorizer doesn't recognize similar loads rguenth at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-03-15 12:27 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56625
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |WAITING
Last reconfirmed| |2013-03-15
Ever Confirmed|0 |1
Build|4.8.0 20130313 |
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-15 12:27:08 UTC ---
For me cselim already sinks the store, making this a non-issue (and vectorizing
the loop). On x86_64, that is.
So - which target?
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/56625] After if-conversion vectorizer doesn't recognize similar loads
2013-03-15 12:18 [Bug tree-optimization/56625] New: After if-conversion vectorizer doesn't recognize similar stores michael.v.zolotukhin at gmail dot com
2013-03-15 12:27 ` [Bug tree-optimization/56625] " rguenth at gcc dot gnu.org
@ 2013-03-15 12:30 ` rguenth at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-03-15 12:30 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56625
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
Summary|After if-conversion |After if-conversion
|vectorizer doesn't |vectorizer doesn't
|recognize similar stores |recognize similar loads
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-15 12:29:50 UTC ---
Oh, it's about the loads!
<bb 3>:
# i_22 = PHI <i_19(4), 0(2)>
# ivtmp_28 = PHI <ivtmp_24(4), 100(2)>
_5 = (long unsigned int) i_22;
_6 = _5 * 8;
_8 = a_7(D) + _6;
_9 = *_8;
_11 = b_10(D) + _6;
_12 = *_11;
_13 = _12 * 4.0e+0;
_15 = b_10(D) + _6;
_16 = *_15;
_17 = _16 * 3.0e+0;
cstore_18 = _9 == 0.0 ? _13 : _17;
*_8 = cstore_18;
and
t.c:4: note: versioning for alias required: can't determine dependence between
*_11 and *_8
t.c:4: note: mark for run-time aliasing test between *_11 and *_8
t.c:4: note: versioning for alias required: can't determine dependence between
*_15 and *_8
t.c:4: note: mark for run-time aliasing test between *_15 and *_8
Creating dr for *_11
analyze_innermost: success.
base_address: b_10(D)
offset from base address: 0
constant offset from base address: 0
step: 8
aligned to: 128
base_object: *b_10(D)
Access function 0: {0B, +, 8}_1
Creating dr for *_15
analyze_innermost: success.
base_address: b_10(D)
offset from base address: 0
constant offset from base address: 0
step: 8
aligned to: 128
base_object: *b_10(D)
Access function 0: {0B, +, 8}_1
somehow the equality test (which we have!) doesn't work here.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-03-15 12:18 [Bug tree-optimization/56625] New: After if-conversion vectorizer doesn't recognize similar stores michael.v.zolotukhin at gmail dot com
2013-03-15 12:27 ` [Bug tree-optimization/56625] " rguenth at gcc dot gnu.org
2013-03-15 12:30 ` [Bug tree-optimization/56625] After if-conversion vectorizer doesn't recognize similar loads rguenth at gcc dot gnu.org
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