3.4 Options Reference

optimization. Setting -xipo_build reduces compile time by avoiding optimizations during the initial pass and optimizing only at link time. Optimization is not needed for the object files, as with -xipo it will be performed at link time. If unoptimized object files built with -xipo_build are linked without including -xipo to perform optimization, the application will fail to link with an unresolved symbol error.

3.4.138.1 -xipo_build Examples

The following example performs a fast build of .o files, followed by crossfile optimization at link time:

%cc -O -xipo -xipo_build -o code1.o -c code1.c

%cc -O -xipo -xipo_build -o code2.o -c code2.c

%cc -O -xipo -o a.out code1.o code2.o

The -xipo_build will turn off -O when creating the .o files, to build these quickly. Full -O optimization will be performed at link time as part of -xipo crossfile optimization.

The following example links without using -xipo.

% cc -O -o a.out code1.o code2.o

If either code1.o or code2.o were generated with -xipo_build, the result will be a link-time failure indicating the symbol __unoptimized_object_file is unresolved.

When building .o files separately, the default behavior is -xipo_build=no. However, when the executable or library is built in a single pass from source files, -xipo_build will be implicitly enabled. For example:

% cc -fast -xipo a.c b.c c.c

will implicitly enable -xipo_build=yes for the first passes that generate a.o, b.o, and c.o. Include the option -xipo_build=no to disable this behavior.

3.4.139 –xivdep[=p]

Disable or set interpretation of !DIR$ IVDEP directives

The IVDEP directive tells the compiler to ignore some or all loop-carried dependences on array references that it finds in a loop, allowing it to perform various loop optimizations such as microvectorization, distribution, software pipelining, among others, that would not be otherwise