* [Bug middle-end/111845] [14 regression] ICE when building pycryptodome
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From: pinskia at gcc dot gnu.org @ 2023-10-17 5:27 UTC (permalink / raw)
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Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |ice-on-valid-code
Target Milestone|--- |14.0
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--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 56126
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56126&action=edit
Reduced testcase
I am not a fan of this reduced testcase since it depends on uninitialized
variables.
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From: pinskia at gcc dot gnu.org @ 2023-10-17 5:42 UTC (permalink / raw)
To: gcc-bugs
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Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2023-10-17
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
It is .UADDC production somehow but I am not sure what is being tried here
since there are almost no detail dumps from widening_mul either.
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--- Comment #3 from Sam James <sjames at gcc dot gnu.org> ---
Created attachment 56127
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56127&action=edit
reduced.ii
I've attached what cvise gave me but it also relies on uninitialised vars (not
tried to fix it yet)
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From: sjames at gcc dot gnu.org @ 2023-10-17 5:50 UTC (permalink / raw)
To: gcc-bugs
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Sam James <sjames at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Attachment #56127|0 |1
is obsolete| |
--- Comment #4 from Sam James <sjames at gcc dot gnu.org> ---
Created attachment 56128
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56128&action=edit
reduced.i
how about that?
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--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 56129
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56129&action=edit
no uninitialized variable in this testcase
This slightly changed testcase from Sam's testcase which removes the
uninitialized variable (just made it an argument)
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From: rguenth at gcc dot gnu.org @ 2023-10-17 6:56 UTC (permalink / raw)
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Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P1
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From: jakub at gcc dot gnu.org @ 2023-10-17 11:37 UTC (permalink / raw)
To: gcc-bugs
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--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Same with renamed vars, so that the long variable names don't make it
unreadable:
int a, b;
unsigned int c, d, e;
void
foo (int x)
{
b += d;
c += b < d;
b += e = a < x;
c += b;
c += b < e;
}
I believe the above is equivalent to:
e = a < x;
unsigned c1;
b = __builtin_addc (b, d, e, &c1);
c = __builtin_addc (c, b, c1, &c1);
i.e. b is set to b + d + e where e is in [0, 1] range and c is set to c + b +
carry-out
from the b + d + e additions.
match_uaddc_usubc is called on the _17 = _30 + _31; addition in:
b.0_1 = b;
b.1_2 = (unsigned int) b.0_1;
d.2_3 = d;
_8 = .ADD_OVERFLOW (b.1_2, d.2_3);
_4 = REALPART_EXPR <_8>;
_14 = IMAGPART_EXPR <_8>;
_5 = _14 != 0;
_6 = (unsigned int) _5;
c.6_7 = c;
_31 = _6 + c.6_7;
a.7_9 = a;
_10 = a.7_9 < x_19(D);
_11 = (unsigned int) _10;
e = _11;
_29 = .ADD_OVERFLOW (_4, _11);
_12 = REALPART_EXPR <_29>;
_28 = IMAGPART_EXPR <_29>;
_13 = (int) _12;
b = _13;
_15 = _28 != 0;
_16 = (unsigned int) _15;
_30 = _12 + _16;
_17 = _30 + _31;
c = _17;
return;
and changes it:
@@ -12,14 +12,14 @@ a.7_9 = a;
_10 = a.7_9 < x_19(D);
_11 = (unsigned int) _10;
e = _11;
+_27 = .UADDC (b.1_2, d.2_3, _11);
_29 = .ADD_OVERFLOW (_4, _11);
-_12 = REALPART_EXPR <_29>;
-_28 = IMAGPART_EXPR <_29>;
+_12 = REALPART_EXPR <_27>;
_13 = (int) _12;
b = _13;
-_15 = _28 != 0;
-_16 = (unsigned int) _15;
_30 = _12 + _16;
-_17 = _30 + _31;
+_26 = IMAGPART_EXPR <_27>;
+_25 = .UADDC (c.6_7, _12, _26);
+_17 = REALPART_EXPR <_25>;
c = _17;
return;
That again looks correct to me, except that the dead _30 = _12 + _16 statement
should have been removed as well but wasn't. The bb contains still other dead
statements
but the _30 = _12 + _16; is the only problematic one, as it refers to released
SSA_NAME. After a fast DCE I think the bb would turn into:
b.0_1 = b;
b.1_2 = (unsigned int) b.0_1;
d.2_3 = d;
c.6_7 = c;
a.7_9 = a;
_10 = a.7_9 < x_19(D);
_11 = (unsigned int) _10;
e = _11;
_27 = .UADDC (b.1_2, d.2_3, _11);
_12 = REALPART_EXPR <_27>;
_13 = (int) _12;
b = _13;
_26 = IMAGPART_EXPR <_27>;
_25 = .UADDC (c.6_7, _12, _26);
_17 = REALPART_EXPR <_25>;
c = _17;
return;
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From: sjames at gcc dot gnu.org @ 2023-10-17 13:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111845
Sam James <sjames at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|[14 regression] ICE when |[14 regression] ICE when
|building pycryptodome |building pycryptodome since
| |r14-1837-g43a3252c42af12
--- Comment #7 from Sam James <sjames at gcc dot gnu.org> ---
Bisect indicates:
43a3252c42af12ad90082e4088ea58eecd0bf582 is the first bad commit
commit 43a3252c42af12ad90082e4088ea58eecd0bf582
Author: Jakub Jelinek <jakub@redhat.com>
Date: Thu Jun 15 09:12:40 2023 +0200
middle-end, i386: Pattern recognize add/subtract with carry [PR79173]
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From: jakub at gcc dot gnu.org @ 2023-10-17 14:18 UTC (permalink / raw)
To: gcc-bugs
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Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org
--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 56133
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56133&action=edit
gcc14-pr111845.patch
Untested fix.
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From: cvs-commit at gcc dot gnu.org @ 2023-10-18 10:38 UTC (permalink / raw)
To: gcc-bugs
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--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:f1744dd50bb1661c98b694ff907cb0a1be4f6134
commit r14-4719-gf1744dd50bb1661c98b694ff907cb0a1be4f6134
Author: Jakub Jelinek <jakub@redhat.com>
Date: Wed Oct 18 12:37:40 2023 +0200
tree-ssa-math-opts: Fix up match_uaddc_usubc [PR111845]
GCC ICEs on the first testcase. Successful match_uaddc_usubc ends up with
some dead stmts which DCE will remove (hopefully) later all.
The ICE is because one of the dead stmts refers to a freed SSA_NAME.
The code already gsi_removes a couple of stmts in the
/* Remove some statements which can't be kept in the IL because they
use SSA_NAME whose setter is going to be removed too. */
section for the same reason (the reason for the freed SSA_NAMEs is that
we don't really have a replacement for those cases - all we have after
a match is combined overflow from the addition/subtraction of 2 operands +
a
[0, 1] carry in, but not the individual overflows from the former 2
additions), but for the last (most significant) limb case, where we try
to match x = op1 + op2 + carry1 + carry2; or
x = op1 - op2 - carry1 - carry2; we just gsi_replace the final stmt, but
left around the 2 temporary stmts as dead; if we were unlucky enough that
those referenced the carry flag that went away, it ICEs.
So, the following patch remembers those temporary statements (rather than
trying to rediscover them more expensively) and removes them before the
final one is replaced.
While working on it, I've noticed we didn't support all the reassociated
possibilities of writing the addition of 4 operands or subtracting 3
operands from one, we supported e.g.
x = ((op1 + op2) + op3) + op4;
x = op1 + ((op2 + op3) + op4);
but not
x = (op1 + (op2 + op3)) + op4;
x = op1 + (op2 + (op3 + op4));
Fixed by the change to inspect also rhs[2] when rhs[1] didn't yield what
we were searching for (if non-NULL) - rhs[0] is inspected in the first
loop and has different handling for the MINUS_EXPR case.
2023-10-18 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/111845
* tree-ssa-math-opts.cc (match_uaddc_usubc): Remember temporary
statements for the 4 operand addition or subtraction of 3 operands
from 1 operand cases and remove them when successful. Look for
nested additions even from rhs[2], not just rhs[1].
* gcc.dg/pr111845.c: New test.
* gcc.target/i386/pr111845.c: New test.
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From: jakub at gcc dot gnu.org @ 2023-10-18 10:39 UTC (permalink / raw)
To: gcc-bugs
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Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Should be fixed now, sorry for introducing this.
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--- Comment #11 from Sam James <sjames at gcc dot gnu.org> ---
Thank you for the quick fix!
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