[Bug target/15852] New: issues related to floating point precision

["sliwa at theta1 dot cft dot edu dot pl" <gcc-bugzilla at gcc dot gnu dot org>]

-ffloat-store requires rewriting existing code. Some libraries, like LAPACK and 
SLATEC, require fp arithmetic at IEEE single/double precision, and are heavily 
affected by the way floating point code is handled by gcc.

In my opinion, these violates pragmatics of the single/double types:

1. floating point conversions do not round the values, e.g. a double converted 
to single remains long double in the register (the conversion is performed only 
on assignment to a variable when -ffloat-store is in effect)

2. comparisons are performed on the long double values from the registers, not 
on the values rounded to the appropriate precision, hence comparison does not 
result in equality, even if it takes place at the appropriate precision level 
(single/double), e.g. 0.1 + 0.4 > 0.5 in floats, altough it's not

-- 
           Summary: issues related to floating point precision
           Product: gcc
           Version: 3.3.2
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sliwa at theta1 dot cft dot edu dot pl
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-slackware-linux
  GCC host triplet: i386-slackware-linux
GCC target triplet: i386-slackware-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15852