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* [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong
@ 2022-04-28 1:25 guihaoc at gcc dot gnu.org
2022-04-28 1:28 ` [Bug tree-optimization/105414] " pinskia at gcc dot gnu.org
` (13 more replies)
0 siblings, 14 replies; 15+ messages in thread
From: guihaoc at gcc dot gnu.org @ 2022-04-28 1:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
Bug ID: 105414
Summary: constant folding for fmin/max(snan, snan) is wrong
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: guihaoc at gcc dot gnu.org
Target Milestone: ---
gcc -O0 -fsignaling-nans -D_WANT_SNAN -lm -o fmin fmin.c && ./fmin
(snan, snan), fmin: nan
gcc -O3 -fsignaling-nans -D_WANT_SNAN -lm -o fmin fmin.c && ./fmin
(snan, snan), fmin: snan
The fmin(SNaN, SNaN) got different result with O0 and O3. The result should be
nan(QNaN) according to C standard.
The problem might be at match.pd. fmin(a,a) can't be folded to a when a is
SNaN. I propose following patch to fix it.
diff --git a/gcc/match.pd b/gcc/match.pd
index cad61848daa..2c2efda158b 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3093,7 +3093,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(for minmax (min max FMIN_ALL FMAX_ALL)
(simplify
(minmax @0 @0)
- @0))
+ (if(!HONOR_SNANS (@0) || !TREE_REAL_CST (@0).signalling)
+ @0)))
/* min(max(x,y),y) -> y. */
(simplify
(min:c (max:c @0 @1) @1)
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
@ 2022-04-28 1:28 ` pinskia at gcc dot gnu.org
2022-04-28 1:31 ` guihaoc at gcc dot gnu.org
` (12 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-04-28 1:28 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
What target is this on?
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
2022-04-28 1:28 ` [Bug tree-optimization/105414] " pinskia at gcc dot gnu.org
@ 2022-04-28 1:31 ` guihaoc at gcc dot gnu.org
2022-04-28 3:07 ` guihaoc at gcc dot gnu.org
` (11 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: guihaoc at gcc dot gnu.org @ 2022-04-28 1:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #2 from HaoChen Gui <guihaoc at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> What target is this on?
I tested it on ppc64le. But I think it should be on all targets?
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
2022-04-28 1:28 ` [Bug tree-optimization/105414] " pinskia at gcc dot gnu.org
2022-04-28 1:31 ` guihaoc at gcc dot gnu.org
@ 2022-04-28 3:07 ` guihaoc at gcc dot gnu.org
2022-04-28 7:07 ` rguenth at gcc dot gnu.org
` (10 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: guihaoc at gcc dot gnu.org @ 2022-04-28 3:07 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #3 from HaoChen Gui <guihaoc at gcc dot gnu.org> ---
For fmin/max behavior, I referred the this ticket.
https://sourceware.org/bugzilla/show_bug.cgi?id=20947
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (2 preceding siblings ...)
2022-04-28 3:07 ` guihaoc at gcc dot gnu.org
@ 2022-04-28 7:07 ` rguenth at gcc dot gnu.org
2022-04-28 7:51 ` jakub at gcc dot gnu.org
` (9 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-04-28 7:07 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2022-04-28
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
I think you want
(if (!tree_expr_maybe_signaling_nan_p (@0))
...
instead.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (3 preceding siblings ...)
2022-04-28 7:07 ` rguenth at gcc dot gnu.org
@ 2022-04-28 7:51 ` jakub at gcc dot gnu.org
2022-04-28 8:10 ` guihaoc at gcc dot gnu.org
` (8 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-04-28 7:51 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Yeah, TREE_REAL_CST can't be used on @0 if it isn't a REAL_CST which nothing
guarantees.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (4 preceding siblings ...)
2022-04-28 7:51 ` jakub at gcc dot gnu.org
@ 2022-04-28 8:10 ` guihaoc at gcc dot gnu.org
2022-04-28 8:18 ` jakub at gcc dot gnu.org
` (7 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: guihaoc at gcc dot gnu.org @ 2022-04-28 8:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #6 from HaoChen Gui <guihaoc at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #4)
> I think you want
>
> (if (!tree_expr_maybe_signaling_nan_p (@0))
> ...
>
> instead.
Thanks so much for comments. Do we have a way to return a NaN directly in
match.pd when both arguments are sNaN?
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (5 preceding siblings ...)
2022-04-28 8:10 ` guihaoc at gcc dot gnu.org
@ 2022-04-28 8:18 ` jakub at gcc dot gnu.org
2022-04-29 10:02 ` guihaoc at gcc dot gnu.org
` (6 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-04-28 8:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Sure, but you don't want to do that at least if flag_trapping_math.
Otherwise, the predicate would be tree_expr_signaling_nan_p and real_nan
function with "", 1 as the middle 2 arguments can create it. But note that
nothing in match.pd does that right now, so I don't think we should do it in
this case either.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (6 preceding siblings ...)
2022-04-28 8:18 ` jakub at gcc dot gnu.org
@ 2022-04-29 10:02 ` guihaoc at gcc dot gnu.org
2022-04-29 10:06 ` jakub at gcc dot gnu.org
` (5 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: guihaoc at gcc dot gnu.org @ 2022-04-29 10:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #8 from HaoChen Gui <guihaoc at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #7)
> Sure, but you don't want to do that at least if flag_trapping_math.
> Otherwise, the predicate would be tree_expr_signaling_nan_p and real_nan
> function with "", 1 as the middle 2 arguments can create it. But note that
> nothing in match.pd does that right now, so I don't think we should do it in
> this case either.
If either of arguments is sNaN, fmin/max should return a qNaN. So I really want
to create a pattern in match.pd to do this. It needs to create a qNaN and
return it. I can't find an existing example in match.pd. Seems the return
value should be relevant to the arguments?
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (7 preceding siblings ...)
2022-04-29 10:02 ` guihaoc at gcc dot gnu.org
@ 2022-04-29 10:06 ` jakub at gcc dot gnu.org
2022-04-29 12:21 ` rguenth at gcc dot gnu.org
` (4 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-04-29 10:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to HaoChen Gui from comment #8)
> (In reply to Jakub Jelinek from comment #7)
> > Sure, but you don't want to do that at least if flag_trapping_math.
> > Otherwise, the predicate would be tree_expr_signaling_nan_p and real_nan
> > function with "", 1 as the middle 2 arguments can create it. But note that
> > nothing in match.pd does that right now, so I don't think we should do it in
> > this case either.
>
> If either of arguments is sNaN, fmin/max should return a qNaN. So I really
> want to create a pattern in match.pd to do this. It needs to create a qNaN
A sNaN should primarily raise an exception or raise a signal when used.
So better not to fold it.
Given that we don't fold anything else with sNaN, starting from sNaN + whatever
etc., just folding it for something so rare as fmin/fmax would be weird.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (8 preceding siblings ...)
2022-04-29 10:06 ` jakub at gcc dot gnu.org
@ 2022-04-29 12:21 ` rguenth at gcc dot gnu.org
2022-05-11 1:32 ` cvs-commit at gcc dot gnu.org
` (3 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-04-29 12:21 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #9)
> (In reply to HaoChen Gui from comment #8)
> > (In reply to Jakub Jelinek from comment #7)
> > > Sure, but you don't want to do that at least if flag_trapping_math.
> > > Otherwise, the predicate would be tree_expr_signaling_nan_p and real_nan
> > > function with "", 1 as the middle 2 arguments can create it. But note that
> > > nothing in match.pd does that right now, so I don't think we should do it in
> > > this case either.
> >
> > If either of arguments is sNaN, fmin/max should return a qNaN. So I really
> > want to create a pattern in match.pd to do this. It needs to create a qNaN
>
> A sNaN should primarily raise an exception or raise a signal when used.
> So better not to fold it.
> Given that we don't fold anything else with sNaN, starting from sNaN +
> whatever
> etc., just folding it for something so rare as fmin/fmax would be weird.
Agreed btw. Iff then such propagation / simplification should belong in
a pass like forwprop or value-numbering which can do this in a cheaper way
than adding patterns for all kinds of operations with NaNs. One might also
say that we should diagnose any arithmetic with known NaNs ...
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (9 preceding siblings ...)
2022-04-29 12:21 ` rguenth at gcc dot gnu.org
@ 2022-05-11 1:32 ` cvs-commit at gcc dot gnu.org
2022-05-12 2:54 ` guihaoc at gcc dot gnu.org
` (2 subsequent siblings)
13 siblings, 0 replies; 15+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-05-11 1:32 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by HaoChen Gui <guihaoc@gcc.gnu.org>:
https://gcc.gnu.org/g:344e425340e3c8e4539b43bf8f661e02c5a5b9a0
commit r13-280-g344e425340e3c8e4539b43bf8f661e02c5a5b9a0
Author: Haochen Gui <guihaoc@gcc.gnu.org>
Date: Mon May 9 17:34:23 2022 +0800
This patch skips constant folding for fmin/max when either argument is
sNaN. According to C standard, fmin(sNaN, sNaNï¼= qNaN, fmin(sNaN, NaN) =
qNaN.
gcc/
PR target/105414
* match.pd (minmax): Skip constant folding for fmin/fmax when both
arguments are sNaN or one is sNaN and another is NaN.
gcc/testsuite/
PR target/105414
* gcc.dg/pr105414.c: New.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (10 preceding siblings ...)
2022-05-11 1:32 ` cvs-commit at gcc dot gnu.org
@ 2022-05-12 2:54 ` guihaoc at gcc dot gnu.org
2022-09-28 10:05 ` cvs-commit at gcc dot gnu.org
2022-11-07 4:48 ` pinskia at gcc dot gnu.org
13 siblings, 0 replies; 15+ messages in thread
From: guihaoc at gcc dot gnu.org @ 2022-05-12 2:54 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
HaoChen Gui <guihaoc at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|NEW |RESOLVED
--- Comment #12 from HaoChen Gui <guihaoc at gcc dot gnu.org> ---
Fixed.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (11 preceding siblings ...)
2022-05-12 2:54 ` guihaoc at gcc dot gnu.org
@ 2022-09-28 10:05 ` cvs-commit at gcc dot gnu.org
2022-11-07 4:48 ` pinskia at gcc dot gnu.org
13 siblings, 0 replies; 15+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-09-28 10:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
--- Comment #13 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Xi Ruoyao <xry111@gcc.gnu.org>:
https://gcc.gnu.org/g:b48d7ff3570fa0ebe7790275cf020d8885120338
commit r13-2914-gb48d7ff3570fa0ebe7790275cf020d8885120338
Author: Xi Ruoyao <xry111@xry111.site>
Date: Sat Sep 24 20:47:22 2022 +0800
LoongArch: Use UNSPEC for fmin/fmax RTL pattern [PR105414]
I made a mistake defining fmin/fmax RTL patterns in r13-2085: I used
smin and smax in the definition mistakenly. This causes the optimizer
to perform constant folding as if fmin/fmax was "really" smin/smax
operations even with -fsignaling-nans. Then pr105414.c fails.
We don't have fmin/fmax RTL codes for now (PR107013) so we can only use
an UNSPEC for fmin and fmax patterns.
gcc/ChangeLog:
PR tree-optimization/105414
* config/loongarch/loongarch.md (UNSPEC_FMAX): New unspec.
(UNSPEC_FMIN): Likewise.
(fmax<mode>3): Use UNSPEC_FMAX instead of smax.
(fmin<mode>3): Use UNSPEC_FMIN instead of smin.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [Bug tree-optimization/105414] constant folding for fmin/max(snan, snan) is wrong
2022-04-28 1:25 [Bug tree-optimization/105414] New: constant folding for fmin/max(snan, snan) is wrong guihaoc at gcc dot gnu.org
` (12 preceding siblings ...)
2022-09-28 10:05 ` cvs-commit at gcc dot gnu.org
@ 2022-11-07 4:48 ` pinskia at gcc dot gnu.org
13 siblings, 0 replies; 15+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-11-07 4:48 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105414
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |13.0
^ permalink raw reply [flat|nested] 15+ messages in thread
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