AIX 5L with IBM XL Compilers SPEC CPU Flags

Invoke the IBM Feedback Directed Program Restructuring FDO utility.

Perform optimizations for maximum performance. This includes maximum interprocedural analysis on all of the objects presented on the "link" step. This level of optimization will increase the compiler's memory usage and compile time requirements. -O5 Provides all of the functionality of the -O4 option, but also provides the functionality of the -qipa=level=2 option.

-O5 is equivalent to the following flags

Perform optimizations for maximum performance. This includes interprocedural analysis on all of the objects presented on the "link" step.

-O4 is equivalent to the following flags

-O3 Performs additional optimizations that are memory intensive, compile-time intensive, and may change the semantics of the program slightly, unless -qstrict is specified. We recommend these optimizations when the desire for run-time speed improvements outweighs the concern for limiting compile-time resources.

-O2 Performs a set of optimizations that are intended to offer improved performance without an unreasonable increase in time or storage that is required for compilation.

-O enables the level of optimization that represents the best tradeoff between compilation speed and run-time performance. If you need a specific level of optimization, specify the appropriate numeric value. Currently, -O is equivalent to -O2.

Performs high-order transformations on loops during optimization.

Produces object code containg instructins that will run on the specified processors. "auto" selects the processor the complile is being done on. "pwr5x" is the POWER5+ processor.

Supported values for this flag are

• auto
Slect
• pwr5x
• pwr5
• pwr4
• ppc970

Specifies the architecture system for which the executable program is optimized. This includes instruction scheduling and cache setting. The supported values for suboption are:

• auto
Use the processor on which the program is compiled.
• pwr5x
The POWER5+ processor based systems.
• pwr5
The POWER5 processor based systems.
• pwr4
The POWER4 processor based systems.
• ppc970
The PPC970 processor based systems.

qipa enhances optimization by doing detailed analysis across procedures (interprocedural analysis or IPA).

level determines the amount of interprocedural analysis and optimization that is performed

level=0 Does only minimal interprocedural analysis and optimization

level=1 turns on inlining , limited alias analysis, and limited call-site tailoring

level=2 turns on full interprocedural data flow and alias analysis

noobject Specifies whether to include standard object code in the object files. Specifying the noobject suboption can substantially reduce overall compilation time, by not generating object code during the first IPA phase.

threads threads[=N] runs the number of parallel threads that are available, or as specified by N. N must be a positive integer. nothreads does not run any parallel threads. This is equivalent to running one serial thread. Specifying -qipa=threads can reduce IPA optimization time. The threads suboption allows the IPA optimizer to run portions of the optimization process in parallel threads, which can speed up the compilation process on multi-processor systems.

Indicates that the compiler understands how to do alloca().

Causes AIX to define "ischar()" (and friends) as macro's and no subroutines.

Causes C++ compiled routines to use pooled memory allocation.

The __IBM_FAST_VECTOR macro defines a different iterator for the std::vector template class. This iterator results in faster code, but is not compatible with code using the default iterator for a std::vector template class. All uses of std::vector for a data type must use the same iterator. Add -D__IBM_FAST_VECTOR to the compile line, or "#define __IBM_FAST_VECTOR 1" to your source code to use the faster iterator for std::vector template class. You must compile all sources with this macro.

Generates 64 bit ABI binaries.

           Specifies what aggregate alignment rules the
                compiler uses for file compilation, where the
                alignment options are:

                bit_packed
                     The compiler uses the bit_packed alignment
                     rules.
                full
                     The compiler uses the RISC System/6000
                     alignment rules. This is the same as power.
                mac68k
                     The compiler uses the Macintosh alignment
                     rules.  This suboption is valid only for 32-
                     bit compilations.
                natural
                     The compiler maps structure members to their
                     natural boundaries.
                packed
                     The compiler uses the packed alignment rules.
                power
                     The compiler uses the RISC System/6000
                     alignment rules.
                twobyte
                     The compiler uses the Macintosh alignment
                     rules.  This suboption is valid only for 32-
                     bit compilations.  The mac68k option is the
                     same as twobyte.

                The default is -qalign=full.

Sets the bit in the file's XCOFF header indicating that this executable will request the use of large pages when they are available on the system and when the user has an appropriate privilege

Indicates that a program, designed to execute in a large page memory environment, can take advantage of large 16 MB pages provided on POWER4 and higher based systems.

Link the mathematical acceleration subsystem libraries (MASS), which contain libraries of tuned mathematical intrinsic functions.

Link the Engineering and Scientifc Subroutine Library (ESSL).

Specifies that, if either -lessl or -lesslsmp are also specified, then Engineering and Scientific Subroutine Library (ESSL) routines should be used in place of some Fortran 90 intrinsic procedures when there is a safe opportunity to do so.

The option used in the first pass of a profile directed feedback compile that causes pdf information to be generated. The profile directed feedback optimization gathers data on both exectuion path and data values. It does not use hardware counters, nor gather any data other than path and data values for PDF specific optimizations.

The option used in the second pass of a profile directed feedback compile that causes PDF information to be utilized during optimization.

Allows most any c dialect.

Cause the C++ compiler to generate Run Time Type Identification code

Causes the Fortran compiler to allocate dynamic arrays on the heap instead of the stack

Indicates that the input fortran source program is in fixed form.

Adds an underscore to global entites to match the C compiler ABI

Causes the compiler to treat "char" variables as signed instead of the default of unsigned.

Invoke the IBM XL C compliler. 32-bit binaries are producded by default.

Invoke the IBM XL C++ compliler. 32-bit binaries are producded by default.

Invoke the IBM XL Fortran compliler. 32-bit binaries are producded by default.

 qalias=ansi | noansi
   If ansi is specified, type-based aliasing is
   used during optimization, which restricts the
   lvalues that can be safely used to access a
   data object. The default is ansi for the xlc,
   xlC, and c89 commands. This option has no
   effect unless you also specify the -O option.

 qalias=std |nostd
 Indicates whether the compilation units contain
 any non-standard aliasing (see Compiler Reference
 for more information). If so, specify nostd. 

specifies the size of the internal alias table for the compiler to use for alias analysis

Causes the compiler to output a traceback if it abends.

The compiler generates additional symbol information for use by the AIX "fdprpro" code optimizer.

Suppresses the message with the message number specified

Causes the system loader to put the heap in it's own segment of the size specified. This is only required for 32-bit applications, as their segments are 256M.