cvs commit: src/lib/msun/bsdsrc b_log.c b_tgamma.c mathimpl.h

[Bruce Evans]

bde         2005-09-19 11:28:19 UTC

  FreeBSD src repository

  Modified files:
    lib/msun/bsdsrc      b_log.c b_tgamma.c mathimpl.h 
  Log:
  Fixed aliasing bugs in TRUNC() by using the fdlibm macros for access
  to doubles as bits.  fdlibm-1.1 had similar aliasing bugs, but these
  were fixed by NetBSD or Cygnus before a modified version of fdlibm was
  imported in 1994.  TRUNC() is only used by tgamma() and some
  implementation-detail functions.  The aliasing bugs were detected by
  compiling with gcc -O2 but don't seem to have broken tgamma() on i386's
  or amd64's.  They broke my modified version of tgamma().
  
  Moved the definition of TRUNC() to mathimpl.h so that it can be fixed
  in one place, although the general version is even slower than necessary
  because it has to operate on pointers to volatiles to handle its arg
  sometimes being volatile.  Inefficiency of the fdlibm macros slows
  down libm generally, and tgamma() is a relatively unimportant part of
  libm.  The macros act as if on 32-bit words in memory, so they are
  hard to optimize to direct actions on 64-bit double registers for
  (non-i386) machines where this is possible.  The optimization is too
  hard for gcc on amd64's, and declaring variables as volatile makes it
  impossible.
  
  Revision  Changes    Path
  1.8       +1 -4      src/lib/msun/bsdsrc/b_log.c
  1.7       +0 -8      src/lib/msun/bsdsrc/b_tgamma.c
  1.6       +25 -0     src/lib/msun/bsdsrc/mathimpl.h