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* [Bug tree-optimization/68050] SLP vectorization should negate constants to match up + vs -
2015-10-22 10:03 [Bug tree-optimization/68050] New: SLP vectorization should negate constants to match up + vs - rguenth at gcc dot gnu.org
@ 2015-10-22 10:03 ` rguenth at gcc dot gnu.org
2021-08-29 4:39 ` pinskia at gcc dot gnu.org
2021-08-30 7:44 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2015-10-22 10:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68050
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2015-10-22
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Mine.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/68050] New: SLP vectorization should negate constants to match up + vs -
@ 2015-10-22 10:03 rguenth at gcc dot gnu.org
2015-10-22 10:03 ` [Bug tree-optimization/68050] " rguenth at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2015-10-22 10:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68050
Bug ID: 68050
Summary: SLP vectorization should negate constants to match up
+ vs -
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
Blocks: 53947
Target Milestone: ---
double x[1024], y[1024], z[1024];
void foo (double w)
{
int i;
for (i = 0; i < 1023; i+=2)
{
z[i] = x[i] + 3.;
z[i+1] = x[i+1] + -3.;
}
}
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/68050] SLP vectorization should negate constants to match up + vs -
2015-10-22 10:03 [Bug tree-optimization/68050] New: SLP vectorization should negate constants to match up + vs - rguenth at gcc dot gnu.org
2015-10-22 10:03 ` [Bug tree-optimization/68050] " rguenth at gcc dot gnu.org
@ 2021-08-29 4:39 ` pinskia at gcc dot gnu.org
2021-08-30 7:44 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-08-29 4:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68050
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed|2015-10-22 00:00:00 |2021-8-28
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
WE do this now:
<bb 3> [local count: 1063004409]:
# ivtmp.13_20 = PHI <ivtmp.13_15(3), 0(2)>
vect__1.5_14 = MEM <vector(2) double> [(double *)&x + ivtmp.13_20 * 1];
vect__5.7_12 = vect__1.5_14 + { -3.0e+0, -3.0e+0 };
vect__2.6_13 = vect__1.5_14 + { 3.0e+0, 3.0e+0 };
_7 = VEC_PERM_EXPR <vect__2.6_13, vect__5.7_12, { 0, 3 }>;
MEM <vector(2) double> [(double *)&z + ivtmp.13_20 * 1] = _7;
ivtmp.13_15 = ivtmp.13_20 + 16;
if (ivtmp.13_15 != 8192)
goto <bb 3>; [99.00%]
else
goto <bb 4>; [1.00%]
But if we use long instead of double, we get:
<bb 3> [local count: 1063004409]:
# ivtmp.12_20 = PHI <ivtmp.12_15(3), 0(2)>
vect__1.5_14 = MEM <vector(2) long int> [(long int *)&x + ivtmp.12_20 * 1];
vect__2.6_13 = vect__1.5_14 + { 3, -3 };
MEM <vector(2) long int> [(long int *)&z + ivtmp.12_20 * 1] = vect__2.6_13;
ivtmp.12_15 = ivtmp.12_20 + 16;
if (ivtmp.12_15 != 8192)
goto <bb 3>; [99.00%]
else
goto <bb 4>; [1.00%]
Note clang has worse code for the VECT_PERM_EXPR but does the same thing as GCC
here.
So the difference between long and double for GCC at least comes from having IR
difference in that the "a - 3" in the long case is actually "a + -3".
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/68050] SLP vectorization should negate constants to match up + vs -
2015-10-22 10:03 [Bug tree-optimization/68050] New: SLP vectorization should negate constants to match up + vs - rguenth at gcc dot gnu.org
2015-10-22 10:03 ` [Bug tree-optimization/68050] " rguenth at gcc dot gnu.org
2021-08-29 4:39 ` pinskia at gcc dot gnu.org
@ 2021-08-30 7:44 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2021-08-30 7:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68050
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
We don't really do it as you show - instead of
vect__5.7_12 = vect__1.5_14 + { -3.0e+0, -3.0e+0 };
vect__2.6_13 = vect__1.5_14 + { 3.0e+0, 3.0e+0 };
_7 = VEC_PERM_EXPR <vect__2.6_13, vect__5.7_12, { 0, 3 }>;
we'd like to see
_7 = vect__1.5_14 + { 3.0e+0, -3.0e+0 };
which is what we should cost as well.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-10-22 10:03 [Bug tree-optimization/68050] New: SLP vectorization should negate constants to match up + vs - rguenth at gcc dot gnu.org
2015-10-22 10:03 ` [Bug tree-optimization/68050] " rguenth at gcc dot gnu.org
2021-08-29 4:39 ` pinskia at gcc dot gnu.org
2021-08-30 7:44 ` rguenth at gcc dot gnu.org
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