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

-qcache Option
Syntax
-qcache=
{
assoc=number |
auto |
cost=cycles |
level=level |
line=bytes |
size=Kbytes |
type={C|c|D|d|I|i}
}[:...]
Specifies the cache configuration for a specific execution machine. The compiler
uses this information to tune program performance, especially for loop operations
that can be structured (or blocked) to process only the amount of data that can fit
into the data cache.
If you know exactly what type of system a program is intended to be executed on
and that system has its instruction or data cache configured differently from the
default case (as governed by the -qtune setting), you can specify the exact
characteristics of the cache to allow the compiler to compute more precisely the
benefits of particular cache-related optimizations.
For the -qcache option to have any effect, you must include the level and type
suboptions and specify at least level 2 of -O.
v
v
v
If you know some but not all of the values, specify the ones you do know.
If a system has more than one level of cache, use a separate -qcache option to
describe each level. If you have limited time to spend experimenting with this
option, it is more important to specify the characteristics of the data cache than
of the instruction cache.
If you are not sure of the exact cache sizes of the target systems, use relatively
small estimated values. It is better to have some cache memory that is not used
than to have cache misses or page faults from specifying a cache that is larger
than the target system has.
Arguments
assoc=number
Specifies the set associativity of the cache:
0 Direct-mapped cache
1 Fully associative cache
n > 1 n-way set-associative cache
auto Automatically detects the specific cache configuration of the compiling
machine. It assumes that the execution environment will be the same as
the compilation environment.
cost=cycles
Specifies the performance penalty that results from a cache miss so that the
compiler can decide whether to perform an optimization that might result
in extra cache misses.
level=level
Specifies which level of cache is affected:
1 Basic cache
XL Fortran Compiler-Option Reference 137