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* [Bug libgcc/105669] New: DFP to HF (_Float16) conversions use incorrect rounding
@ 2022-05-20 7:45 clyon at gcc dot gnu.org
2022-05-20 20:22 ` [Bug libgcc/105669] " jsm28 at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: clyon at gcc dot gnu.org @ 2022-05-20 7:45 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105669
Bug ID: 105669
Summary: DFP to HF (_Float16) conversions use incorrect
rounding
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libgcc
Assignee: unassigned at gcc dot gnu.org
Reporter: clyon at gcc dot gnu.org
Target Milestone: ---
Support for conversions between DFP and _Float16 have been introduced with
r13-687-g308a0af4f91324.
For simplicity it uses intermediate conversions with SFmode, leading to double
rounding which probably produces incorrectly rounded results.
See also PR97635
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug libgcc/105669] DFP to HF (_Float16) conversions use incorrect rounding
2022-05-20 7:45 [Bug libgcc/105669] New: DFP to HF (_Float16) conversions use incorrect rounding clyon at gcc dot gnu.org
@ 2022-05-20 20:22 ` jsm28 at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: jsm28 at gcc dot gnu.org @ 2022-05-20 20:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105669
Joseph S. Myers <jsm28 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2022-05-20
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #1 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
Example test illustrating this bug, at least on x86_64 (the DFP input is very
close to half way between two consecutive _Float16 values):
extern void exit (int);
extern void abort (void);
#define DCONST 7.340312e-5DF
static const _Float16 f1 = DCONST;
volatile _Decimal32 d = DCONST;
int
main (void)
{
volatile _Float16 f2;
f2 = d;
if (f1 == f2)
exit (0);
else
abort ();
}
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2022-05-20 7:45 [Bug libgcc/105669] New: DFP to HF (_Float16) conversions use incorrect rounding clyon at gcc dot gnu.org
2022-05-20 20:22 ` [Bug libgcc/105669] " jsm28 at gcc dot gnu.org
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