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* [Bug math/18031] New: [ldbl-128ibm] modfl problems
@ 2015-02-25 23:07 jsm28 at gcc dot gnu.org
2020-08-13 11:37 ` [Bug math/18031] " jakub at redhat dot com
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: jsm28 at gcc dot gnu.org @ 2015-02-25 23:07 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=18031
Bug ID: 18031
Summary: [ldbl-128ibm] modfl problems
Product: glibc
Version: 2.21
Status: NEW
Severity: normal
Priority: P2
Component: math
Assignee: unassigned at sourceware dot org
Reporter: jsm28 at gcc dot gnu.org
The ldbl-128ibm implementation of modfl has several issues:
* In the case for high part exponent < 52,
(((i0&i)|(i1&0x7fffffffffffffffLL))==0) is not a correct test for integer
argument; the latter part effectively tests just if the low part is a power of
2. Example: an argument of 0x1.ffffffffffffffp51L is wrongly treated as being
an integer.
* In that case, the handling of non-integers when detected as such fails to
allow for the low part being of opposite sign to the integer high part.
Example: 0x1.ffffffffffffff1p51L produces integer part 0x1p+52, fractional part
-0x1.ep-6.
* The case of high part exponent > 103 is treated as meaning the argument is an
integer, but that's not true even when restricted to numbers with 106
contiguous mantissa bits. Example: 0x1.ffffffffffffffffffffffffff8p104L is
wrongly treated as being an integer.
* In the case for exponents 52 to 103, the test i1&i)==0 for being an integer
is completely bogus; the mask i = -1ULL>>(j0-52) is computed as if this were a
conventional IEEE format. Example: 0x0.fffffffffffffcp52L is wrongly treated
as being an integer.
* When something is detected as not an integer in that case, the INSERT_WORDS64
(xlo, i1&(~i)) is always inserting a subnormal / zero value in the low part,
its exponent having been masked off earlier. Example:
0x1.00000000000001111p56L gets integer part 0x1p+56 and fractional part
0x1.111p+0, which is more than 1.
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* [Bug math/18031] [ldbl-128ibm] modfl problems
2015-02-25 23:07 [Bug math/18031] New: [ldbl-128ibm] modfl problems jsm28 at gcc dot gnu.org
@ 2020-08-13 11:37 ` jakub at redhat dot com
2020-08-13 15:26 ` fw at deneb dot enyo.de
2024-04-24 7:04 ` amodra at gmail dot com
2 siblings, 0 replies; 4+ messages in thread
From: jakub at redhat dot com @ 2020-08-13 11:37 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=18031
Jakub Jelinek <jakub at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |amodra at gmail dot com,
| |jakub at redhat dot com
URL| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=96600
--- Comment #1 from Jakub Jelinek <jakub at redhat dot com> ---
This has been filed today as a gcc bug when it is a glibc bug, see
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96600 for details.
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* [Bug math/18031] [ldbl-128ibm] modfl problems
2015-02-25 23:07 [Bug math/18031] New: [ldbl-128ibm] modfl problems jsm28 at gcc dot gnu.org
2020-08-13 11:37 ` [Bug math/18031] " jakub at redhat dot com
@ 2020-08-13 15:26 ` fw at deneb dot enyo.de
2024-04-24 7:04 ` amodra at gmail dot com
2 siblings, 0 replies; 4+ messages in thread
From: fw at deneb dot enyo.de @ 2020-08-13 15:26 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=18031
Florian Weimer <fw at deneb dot enyo.de> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |fw at deneb dot enyo.de
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=96600
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* [Bug math/18031] [ldbl-128ibm] modfl problems
2015-02-25 23:07 [Bug math/18031] New: [ldbl-128ibm] modfl problems jsm28 at gcc dot gnu.org
2020-08-13 11:37 ` [Bug math/18031] " jakub at redhat dot com
2020-08-13 15:26 ` fw at deneb dot enyo.de
@ 2024-04-24 7:04 ` amodra at gmail dot com
2 siblings, 0 replies; 4+ messages in thread
From: amodra at gmail dot com @ 2024-04-24 7:04 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=18031
Alan Modra <amodra at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC|amodra at gmail dot com |
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2015-02-25 23:07 [Bug math/18031] New: [ldbl-128ibm] modfl problems jsm28 at gcc dot gnu.org
2020-08-13 11:37 ` [Bug math/18031] " jakub at redhat dot com
2020-08-13 15:26 ` fw at deneb dot enyo.de
2024-04-24 7:04 ` amodra at gmail dot com
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