[Bug math/15214] New: cacos, casin, and casinh wrongly underflow ldbl-128ibm

[Bug math/15214] New: cacos, casin, and casinh wrongly underflow ldbl-128ibm

[azanella at linux dot vnet.ibm.com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15214

             Bug #: 15214
           Summary: cacos, casin, and casinh wrongly underflow ldbl-128ibm
           Product: glibc
           Version: 2.17
            Status: NEW
          Severity: minor
          Priority: P2
         Component: math
        AssignedTo: unassigned@sourceware.org
        ReportedBy: azanella@linux.vnet.ibm.com
    Classification: Unclassified


The following math/libm-test.inc tests trigger spurious underflows exceptions
for ldbl-128ibm:

cacos (0x1p500 + 1.0 i)
cacos (0x1p500 - 1.0 i)
cacos (-0x1p500 + 1.0 i)
cacos (-0x1p500 - 1.0 i)
cacos (1.0 + 0x1p500 i)
cacos (-1.0 + 0x1p500 i)
cacos (1.0 - 0x1p500 i)
cacos (-1.0 - 0x1p500 i)
casin (0x1p500 + 1.0 i)
casin (0x1p500 - 1.0 i)
casin (-0x1p500 + 1.0 i)
casin (-0x1p500 - 1.0 i)
casin (1.0 + 0x1p500 i)
casin (-1.0 + 0x1p500 i)
casin (1.0 - 0x1p500 i)
casin (-1.0 - 0x1p500 i)
casinh (0x1p500 + 1.0 i)
casinh (0x1p500 - 1.0 i)
casinh (-0x1p500 + 1.0 i)
casinh (-0x1p500 - 1.0 i)
casinh (1.0 + 0x1p500 i)
casinh (-1.0 + 0x1p500 i)
casinh (1.0 - 0x1p500 i) 
casinh (-1.0 - 0x1p500 i)

This is in fact an issue with __ieee754_logl implementation: in the domain
reduction phase, where the algorithm transform log(u) -> log(t) + log(u/t) and
log(u/t) -> log(1+(u-t)/t), if the input is high enough the calculation
'1+(u-t)/t' might generate subnormal numbers.

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[Bug math/15214] cacos, casin, and casinh wrongly underflow ldbl-128ibm

[azanella at linux dot vnet.ibm.com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15214

Adhemerval Zanella Netto <azanella at linux dot vnet.ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |azanella at linux dot
                   |                            |vnet.ibm.com
         AssignedTo|unassigned at sourceware    |azanella at linux dot
                   |dot org                     |vnet.ibm.com

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[Bug math/15214] cacos, casin, and casinh wrongly underflow ldbl-128ibm

[azanella at linux dot vnet.ibm.com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15214

Adhemerval Zanella Netto <azanella at linux dot vnet.ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #1 from Adhemerval Zanella Netto <azanella at linux dot vnet.ibm.com> 2013-03-28 13:00:18 UTC ---
Fixed with commit fbbe2b9a1f04c00ea0f8820a545bd4ca780ffa30.

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[Bug math/15214] cacos, casin, and casinh wrongly underflow ldbl-128ibm

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=15214

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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