[Bug math/19603] New: [ldbl-128ibm] remainderl, remquol incorrect sign handling in equality tests

["jsm28 at gcc dot gnu.org" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=19603

            Bug ID: 19603
           Summary: [ldbl-128ibm] remainderl, remquol incorrect sign
                    handling in equality tests
           Product: glibc
           Version: 2.23
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: jsm28 at gcc dot gnu.org
  Target Milestone: ---

The ldbl-128ibm implementations of remainderl and remquol have logic resulting
in incorrect tests for equality of the absolute values of the arguments. 
Equality is tested based on the integer representations of the high and low
parts, with the sign bit masked off the high part - but when this changes the
sign of the high part, the sign of the low part needs to be changed as well,
and failure to do this means arguments are wrongly treated as equal when they
are not.  E.g., a remainder of zero is wrongly returned for arguments
(0x0.ffffffffffffffp0L, -0x1.00000000000001p0L).  I have a patch for 2.24.

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