From: Aldy Hernandez <aldyh@redhat.com>
To: Jakub Jelinek <jakub@redhat.com>, GCC Mailing List <gcc@gcc.gnu.org>
Subject: spaceship_replacement cannot see through simplified set of FP conditionals
Date: Fri, 29 Jul 2022 13:40:12 +0200 [thread overview]
Message-ID: <CAGm3qMVmdCFpDSvTSpmHbiK61ekpH4vA3zxNYZ7aOt+UYzg56Q@mail.gmail.com> (raw)
Hi.
With my upcoming patch enabling floating point VRP,
g++.dg/opt/pr94589-2.C is failing:
https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598788.html
The problem is that phiopt no longer sees the following snippet,
because we have folded away the final conditional as true:
bool f5 (double i, double j)
{
signed char __v$_M_value;
signed char c$_M_value;
bool D.8519;
struct partial_ordering __v;
struct partial_ordering c;
unsigned int _11;
bool _16;
<bb 2> :
if (i_2(D) != j_4(D))
goto <bb 3>; [INV]
else
goto <bb 6>; [INV]
<bb 3> :
if (i_2(D) >= j_4(D))
goto <bb 4>; [INV]
else
goto <bb 6>; [INV]
<bb 4> :
if (i_2(D) > j_4(D))
goto <bb 6>; [INV]
else
goto <bb 5>; [INV]
<bb 5> :
<bb 6> :
# c$_M_value_3 = PHI <-1(3), 0(2), 2(5), 1(4)>
_11 = (unsigned int) c$_M_value_3;
_16 = _11 <= 1;
return _16;
}
This means that spaceship_replacement() now sees one less argument to the PHI:
<bb 2> :
if (i_2(D) != j_4(D))
goto <bb 3>; [INV]
else
goto <bb 5>; [INV]
<bb 3> :
if (i_2(D) >= j_4(D))
goto <bb 4>; [INV]
else
goto <bb 5>; [INV]
<bb 4> :
<bb 5> :
# c$_M_value_3 = PHI <-1(3), 0(2), 1(4)>
...and we bail because we are expecting 4 arguments:
if (EDGE_COUNT (phi_bb->preds) != 4)
return false;
Could someone give me a hand here? Can spaceship_replacement easily be
adapted to handle this case, or should we be simplifying this
elsewhere?
Thanks.
Aldy
next reply other threads:[~2022-07-29 11:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-29 11:40 Aldy Hernandez [this message]
2022-07-29 11:49 ` Jakub Jelinek
2022-07-29 11:51 ` Aldy Hernandez
2022-07-29 11:57 ` Jakub Jelinek
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