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* [Bug tree-optimization/108017] New: ptr+v >= ptr + d should converted into (long)v >= CST(/sizeof(*ptr))
@ 2022-12-08 3:52 pinskia at gcc dot gnu.org
2022-12-08 7:07 ` [Bug tree-optimization/108017] " rguenth at gcc dot gnu.org
2022-12-12 20:09 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-12-08 3:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108017
Bug ID: 108017
Summary: ptr+v >= ptr + d should converted into (long)v >=
CST(/sizeof(*ptr))
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Take:
```
_Bool f(int *a, __SIZE_TYPE__ t, __SIZE_TYPE__ t1)
{
int *b = a + t;
int *c = a + t1;
return c >= b;
}
_Bool f1(int *a, __SIZE_TYPE__ t, __SIZE_TYPE__ t1)
{
long tt = t;
long tt1 = t1;
return tt1 >= tt;
}
```
These two should give the same code.
LLVM does this optimization.
I noticed this while looking into the code from the blog at
https://lemire.me/blog/2022/12/06/optimizing-compilers-reload-vector-constants-needlessly/
(but not vector constant issue though).
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/108017] ptr+v >= ptr + d should converted into (long)v >= CST(/sizeof(*ptr))
2022-12-08 3:52 [Bug tree-optimization/108017] New: ptr+v >= ptr + d should converted into (long)v >= CST(/sizeof(*ptr)) pinskia at gcc dot gnu.org
@ 2022-12-08 7:07 ` rguenth at gcc dot gnu.org
2022-12-12 20:09 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-12-08 7:07 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108017
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2022-12-08
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
We do this for &x + C {!=,==} &x' + C' - I think we're afraid of relational
compares here though, even with TYPE_OVERFLOW_UNDEFINED.
/* (&a+b) !=/== (&a[1] + c) -> sizeof(a[0]) + b !=/== c */
(for neeq (ne eq)
(simplify
(neeq (pointer_plus ADDR_EXPR@0 @1) (pointer_plus ADDR_EXPR@2 @3))
(with { poly_int64 diff; tree inner_type = TREE_TYPE (@1);}
(if (ptr_difference_const (@0, @2, &diff))
(neeq (plus { build_int_cst_type (inner_type, diff); } @1) @3)))))
that could be relaxed to general @0/@2 (at some cost) and to
relational compares with TYPE_OVERFLOW_UNDEFINED.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/108017] ptr+v >= ptr + d should converted into (long)v >= CST(/sizeof(*ptr))
2022-12-08 3:52 [Bug tree-optimization/108017] New: ptr+v >= ptr + d should converted into (long)v >= CST(/sizeof(*ptr)) pinskia at gcc dot gnu.org
2022-12-08 7:07 ` [Bug tree-optimization/108017] " rguenth at gcc dot gnu.org
@ 2022-12-12 20:09 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-12-12 20:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108017
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=94356
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I think this is the more generialized form of bug 94356.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-12-12 20:09 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2022-12-08 3:52 [Bug tree-optimization/108017] New: ptr+v >= ptr + d should converted into (long)v >= CST(/sizeof(*ptr)) pinskia at gcc dot gnu.org
2022-12-08 7:07 ` [Bug tree-optimization/108017] " rguenth at gcc dot gnu.org
2022-12-12 20:09 ` pinskia at gcc dot gnu.org
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