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6.5 Support for testing link-time optimizations ¶

Tests for link-time optimizations usually require multiple source files that are compiled separately, perhaps with different sets of options. There are several special-purpose test directives used for these tests.

{ dg-lto-do do-what-keyword }

do-what-keyword specifies how the test is compiled and whether it is executed. It is one of:

assemble

Compile with -c to produce a relocatable object file.

link

Compile, assemble, and link to produce an executable file.

ar-link

Similar to link, but combine all but the first source file into an archive file before the final link.

incr-link

As with ar-link, but combine the files into an object file using incremental linking, rather than an archive file. This enables testing the incremental linking features of the LTO front end.

run

Produce and run an executable file, which is expected to return an exit code of 0.

The default is run. That can be overridden for a set of tests by redefining dg-do-what-default within the .exp file for those tests.

Unlike dg-do, dg-lto-do does not support an optional ‘target’ or ‘xfail’ list. Use dg-skip-if, dg-xfail-if, or dg-xfail-run-if.

{ dg-lto-options { { options } [{ options }] } [{ target selector }]}

This directive provides a list of one or more sets of compiler options to override LTO_OPTIONS. Every test file will be compiled and run once for each of these sets of options. Individual source files within a test may also use dg-options to specify additional options to include.

{ dg-lto-additional-options { { options } [{ options }] } [{ target selector }]}

This is similar to dg-lto-options, but rather than overriding LTO_OPTIONS, it appends the given options to each of the sets specified in LTO_OPTIONS. This can be used to add a given list of options to every compilation of all source files in the test, without otherwise changing which combinations of options are tested.

{ dg-extra-ld-options options [{ target selector }]}

This directive adds options to the linker options used.

{ dg-suppress-ld-options options [{ target selector }]}

This directive removes options from the set of linker options used.