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4
Creating Program-wide and Module-local Optimizations
4-2
i960 Processor Compiler User's Guide
optimization decisions. Throughout this chapter, standard (i.e., non-
program-wide) optimizations are referred to as module-local
optimizations.
About Profiling
The compiler can also collect information about the runtime behavior of a
program by instrumenting the program. The instrumented program can be
executed with typical input data, and the resultant program execution
profile can be used by the global decision making and optimization phase
to improve the performance of the final optimized program. The profile
can also provide input to the global coverage analyzer tool (gcov960),
which gives users information about the runtime behavior of the program
at the source-code level.
Program-wide optimizations are enabled by options that tell the compiler
to:
1. Build a program database during the compilation phase.
2. Invoke a global decision making and optimization step during the
linking phase.
3. Automatically substitute the resulting optimized modules into the final
program during the linking phase.
Specifying the Program Database Directory
The program database directory (PDB) is the repository for all program-
wide optimization information about a particular program. When using
program-wide optimizations, you must specify the correct PDB to all
compilation tools involved in building the program. You initially create
the PDB, but the files within this directory are automatically managed by
the various pieces of the program-wide optimization system. Once this is
done, you do not change the files in the PDB.
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