XL Fortran Enterprise Edition for AIX : User's Guide - IBM

Table 1. Potential Problems Migrating Programs to XL Fortran Version 9 (continued). The
column on the right shows which problems you can avoid by using the xlf or f77 command.
Potential Problem Solution or Workaround xlf Avoids?
The .XOR. intrinsic is not recognized.
Zero-sized objects are not allowed by the
compiler.
Existing programs or programs linked with
older XL Fortran object files run more
slowly or do not show expected
performance improvements on new
hardware.
Programs compiled with -O3 or -qhot
optimization behave differently from those
unoptimized (different results, exceptions,
or compilation messages).
The option combination -O and -1 cannot
be abbreviated -O1, to avoid
misunderstandings. (There are -O2, -O3,
-O4, and -O5 optimization levels, but there
is no -O1.)
Programs that use integer POINTERs
produce incorrect results when optimized.
Use the option
-qxlf77=intxor.
Use the xlf90 or xlf95
command, or use the
-qzerosize option with the
xlf or f77 command.
Performance / Optimization Problems
Recompile everything.
Try adding the -qstrict
option.
Specify -O and -1 as separate
options.
Specify the option
-qalias=intptr with the xlf90
or xlf95 command, or use the
xlf command.
U
U
26 XL Fortran Enterprise Edition for AIX : User’s Guide