You can invoke the compiler by using the xlf, xlf_r, xlf_r7, xlf90, xlf90_r, xlf90_r7, xlf95, xlf95_r, xlf95_r7, f77, or fort77 command. The xlf, xlf_r, xlf_r7, and f77 commands maintain maximum compatibility with the behavior and I/O formats of XL Fortran Version 2. The xlf90, xlf90_r, and xlf90_r7 commands provide more Fortran 90 conformance and some implementation choices for efficiency and usability. The xlf95, xlf95_r, and xlf95_r7 commands provide more Fortran 95 conformance and some implementation choices for efficiency and usability. The fort77 command provides maximum compatibility with the XPG4 behavior.
The main difference between the set of xlf_r, xlf_r7, xlf90_r, xlf90_r7, xlf95_r, and xlf95_r7 commands and the set of xlf, xlf90, xlf95, f77, and fort77 commands is that the first set links and binds the object files to the thread-safe components (libraries, crt0_r.o, and so on). You can have this behavior with the second set of commands by using the -F compiler option to specify the configuration file stanza to use. For example:
xlf -F/etc/xlf.cfg:xlf_r
You can control the actions of the compiler through a set of options. The different categories of options help you to debug, to optimize and tune program performance, to select extensions for compatibility with programs from other platforms, and to do other common tasks that would otherwise require changing the source code.
To simplify the task of managing many different sets of compiler options, you can customize the single file /etc/xlf.cfg instead of creating many separate aliases or shell scripts.
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