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* [Bug middle-end/111324] New: More optimization about "(X * Y) / Y"
@ 2023-09-07 8:53 guojiufu at gcc dot gnu.org
2023-09-07 9:01 ` [Bug middle-end/111324] " guojiufu at gcc dot gnu.org
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: guojiufu at gcc dot gnu.org @ 2023-09-07 8:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111324
Bug ID: 111324
Summary: More optimization about "(X * Y) / Y"
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: guojiufu at gcc dot gnu.org
Target Milestone: ---
For case:
------ t.c
typedef unsigned int INT;
INT
foo (INT x, INT y)
{
if (x > 100 || y > 100)
return 0;
return (x * y) / y;
}
---------
gcc -O2 t.c -S -fdump-tree-optimized
<bb 4> [local count: 467721933]:
_1 = x_3(D) * y_4(D);
_5 = _1 / y_4(D);
<bb 5> [local count: 1073741824]:
# _2 = PHI <0(2), _5(4), 0(3)>
return _2;
While for the below case, it can be optimized.
------
typedef unsigned int INT;
INT
foo (INT x, INT y)
{
if (x > 100 || y > 100)
return 0;
INT x1 = x + 1;
INT y1 = y + 1;
return (x1 * y1) / y1;
}
-------
The "(x1 * y1) / y1" is optimized to "x1".
<bb 4> [local count: 467721933]:
x1_4 = x_2(D) + 1;
<bb 5> [local count: 1073741824]:
# _1 = PHI <0(2), x1_4(4), 0(3)>
return _1;
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/111324] More optimization about "(X * Y) / Y"
2023-09-07 8:53 [Bug middle-end/111324] New: More optimization about "(X * Y) / Y" guojiufu at gcc dot gnu.org
@ 2023-09-07 9:01 ` guojiufu at gcc dot gnu.org
2023-09-07 19:15 ` pinskia at gcc dot gnu.org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: guojiufu at gcc dot gnu.org @ 2023-09-07 9:01 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111324
--- Comment #1 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> ---
In match.pd, there is a pattern:
/* Simplify (t * 2) / 2) -> t. */
(for div (trunc_div ceil_div floor_div round_div exact_div)
(simplify
(div (mult:c @0 @1) @1)
(if (ANY_INTEGRAL_TYPE_P (type))
(if (TYPE_OVERFLOW_UNDEFINED (type))
@0
#if GIMPLE
(with
{
bool overflowed = true;
value_range vr0, vr1;
if (INTEGRAL_TYPE_P (type)
&& get_global_range_query ()->range_of_expr (vr0, @0)
&& get_global_range_query ()->range_of_expr (vr1, @1)
&& !vr0.varying_p () && !vr0.undefined_p ()
&& !vr1.varying_p () && !vr1.undefined_p ())
{
Here, "get_global_range_query" is able to get the value-range info for SSA.
But it does not handle the case t.c. "get_range_query" can handle it.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/111324] More optimization about "(X * Y) / Y"
2023-09-07 8:53 [Bug middle-end/111324] New: More optimization about "(X * Y) / Y" guojiufu at gcc dot gnu.org
2023-09-07 9:01 ` [Bug middle-end/111324] " guojiufu at gcc dot gnu.org
@ 2023-09-07 19:15 ` pinskia at gcc dot gnu.org
2023-09-11 3:26 ` guojiufu at gcc dot gnu.org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-09-07 19:15 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111324
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Keywords| |missed-optimization
Last reconfirmed| |2023-09-07
Severity|normal |enhancement
CC| |pinskia at gcc dot gnu.org
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
So using the local range in this case is ok. There might be only a few times we
don't want to use it though in match.
Here is a testcase where we should just change it into "return x;" but don't
yet:
```
typedef unsigned int INT;
INT
foo (INT x, INT y)
{
if (x > 100 || y > 100)
return x;
return (x * y) / y;
}
```
Note clang is able to change it though.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/111324] More optimization about "(X * Y) / Y"
2023-09-07 8:53 [Bug middle-end/111324] New: More optimization about "(X * Y) / Y" guojiufu at gcc dot gnu.org
2023-09-07 9:01 ` [Bug middle-end/111324] " guojiufu at gcc dot gnu.org
2023-09-07 19:15 ` pinskia at gcc dot gnu.org
@ 2023-09-11 3:26 ` guojiufu at gcc dot gnu.org
2023-09-13 8:43 ` guojiufu at gcc dot gnu.org
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: guojiufu at gcc dot gnu.org @ 2023-09-11 3:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111324
--- Comment #3 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> ---
A patch is posted:
https://gcc.gnu.org/pipermail/gcc-patches/2023-September/629534.html
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/111324] More optimization about "(X * Y) / Y"
2023-09-07 8:53 [Bug middle-end/111324] New: More optimization about "(X * Y) / Y" guojiufu at gcc dot gnu.org
` (2 preceding siblings ...)
2023-09-11 3:26 ` guojiufu at gcc dot gnu.org
@ 2023-09-13 8:43 ` guojiufu at gcc dot gnu.org
2023-09-13 8:59 ` guojiufu at gcc dot gnu.org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: guojiufu at gcc dot gnu.org @ 2023-09-13 8:43 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111324
--- Comment #4 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> ---
(In reply to Jiu Fu Guo from comment #3)
> A patch is posted:
> https://gcc.gnu.org/pipermail/gcc-patches/2023-September/629534.html
It is not for this PR. Sorry for typo.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/111324] More optimization about "(X * Y) / Y"
2023-09-07 8:53 [Bug middle-end/111324] New: More optimization about "(X * Y) / Y" guojiufu at gcc dot gnu.org
` (3 preceding siblings ...)
2023-09-13 8:43 ` guojiufu at gcc dot gnu.org
@ 2023-09-13 8:59 ` guojiufu at gcc dot gnu.org
2023-09-18 2:30 ` guojiufu at gcc dot gnu.org
2023-09-18 2:36 ` guojiufu at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: guojiufu at gcc dot gnu.org @ 2023-09-13 8:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111324
--- Comment #5 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> Confirmed.
>
> So using the local range in this case is ok. There might be only a few times
> we don't want to use it though in match.
Agree, "get_range_query" would be more useful for most cases.
Through a quick look at match.pd, there are another two patterns that use
"get_global_range_query".
Some concerns about those patterns, so those patterns may not need to be
updated.
* (T)(A)+cst -->(T)(A+cst): I'm wondering if this transformation is really in
favor of PPC.
e.g. "return (long) x1 + 40;" could save one "extend-insn" less than "return
(long)(x1 + 40);"
* For pattern "((x * cst) + cst1) * cst2": it seems this pattern does not
affect any cases. I mean this optimization is done by other parts (before
match.pd).
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/111324] More optimization about "(X * Y) / Y"
2023-09-07 8:53 [Bug middle-end/111324] New: More optimization about "(X * Y) / Y" guojiufu at gcc dot gnu.org
` (4 preceding siblings ...)
2023-09-13 8:59 ` guojiufu at gcc dot gnu.org
@ 2023-09-18 2:30 ` guojiufu at gcc dot gnu.org
2023-09-18 2:36 ` guojiufu at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: guojiufu at gcc dot gnu.org @ 2023-09-18 2:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111324
Jiu Fu Guo <guojiufu at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #6 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> ---
This can be handled by r14-3913-g8d8bc560b6ab7f3153db23ffb37157528e5b2c9a.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/111324] More optimization about "(X * Y) / Y"
2023-09-07 8:53 [Bug middle-end/111324] New: More optimization about "(X * Y) / Y" guojiufu at gcc dot gnu.org
` (5 preceding siblings ...)
2023-09-18 2:30 ` guojiufu at gcc dot gnu.org
@ 2023-09-18 2:36 ` guojiufu at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: guojiufu at gcc dot gnu.org @ 2023-09-18 2:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111324
--- Comment #7 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> ---
A comment https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111303#c7
should be attached here.
^ permalink raw reply [flat|nested] 8+ messages in thread
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2023-09-07 19:15 ` pinskia at gcc dot gnu.org
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