z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

function boundaries, even across compilation units. It also performs
optimizations not otherwise available with the z/OS XL C/C++
compiler.
When phase code I (capital letter I) is specified for the compilation
phase, then IPA compilation steps are performed. When phase
code I is specified for the link-editing phase, or when the first
link-editing phase (code l) option is i or I, then an additional IPA
Link step is performed prior to the prelink and link-edit steps.
With conventional compilation and link-editing, the object code
generation takes place during the compilation phase. With IPA
compilation and link-editing, the object code generation takes place
during the link-editing phase. Therefore, you might need to request
listing information about the program (such as with the -V option)
during the link-editing phase.
Unlike the other phase codes, phase code I does not require that
any additional options be specified. If they are, they should be
specified for both the compilation and link-editing phases.
No additional preparation needs to be done in order to use IPA.
Example: To create the executable myIPApgm using c89 with some
existing source program mypgm.c, you could specify:
c89 –W I –o myIPApgm mypgm.c
When IPA is used with c++, and automatic template generation is
being used, phase code I will control whether the automatic
template generation compiles are done using IPA. If you do not
specify phase code I, then regular compiles will be done. Specifying
I as the first option of the link-editing phase option (that is, -W l,I),
will cause the IPA linker to be used, but will not cause the IPA
compiler to be used for automatic template generation unless phase
code I (that is, -W I) is also specified.
The IPA Profile-Directed Feedback (PDF) option tunes
optimizations, where results from sample program execution are
used to improve optimization near conditional branches and in
frequently executed code topics. The profiling information is placed
in the file specified by the PDFNAME(filename) suboption. If
PDFNAME(filename) is not specified, the default name of the file
containing profile information is PDF.
LP64 The LP64 option instructs the compiler to generate AMODE 64
code utilizing the z/Architecture 64-bit instructions.
To compile 64-bit code, specify the z/OS XL C/C++ LP64 compiler
option.
Example: The following example shows how to compile and bind
using the LP64 option:
c89 -o -W c,LP64 -Wl,LP64 file.c
c89, cc, and c++
XPLINK (Extra Performance Linkage)
z/OS XPLINK provides improved performance for many C/C++
programs. The XPLINK compiler option instructs the z/OS XL
C/C++ compiler to generate high performance linkage for
subroutine calls. It does so primarily by making subroutine calls as
fast and efficient as possible, by reducing linkage overhead, and by
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