This directory contains tests for link-time optimization (LTO).

=== Directives ===

The LTO harness recognizes the following special DejaGnu directives:
 *  dg-lto-do - the equivalent of dg-do with a limited set of supported
      arguments (see below),
 *  dg-lto-options - the equivalent of dg-options with additional syntax
      to support different sets of options for different files compiled
      as part of the same test case,
 *  dg-lto-warning - the equivalent of dg-warning for diagnostics expected
      to be emitted at LTO link time,
 *  dg-lto-message - the equivakent of dg-message for informational notes
      expected to be emitted at LTO link time.

=== Test Names ===

Tests in this directory may span multiple files, so the naming of
the files is significant.

The name of every file must end with '_N' where N is an integer.
All the files with the same name base and different _N suffixes
will be compiled separately and linked together to form the final
executable.

By default, each set of files will be compiled with list of
options listed in LTO_OPTIONS (../../lib/lto.exp), which can be
overridden in the shell environment or using the 'dg-lto-options'
directive in the main file of the set (i.e., the file with _0
suffix).

For example, given the files a_0.C a_1.C a_2.C, they will be
compiled as:

$ g++ -c <flags> a_0.C
$ g++ -c <flags> a_1.C
$ g++ -c <flags> a_2.C
$ g++ -o <executable> a_0.o a_1.o a_2.o

Tests that do not need more than one file are a special case
where there is a single file named 'foo_0.C'.

=== The dg-lto-do Directive ==

The only supported dg-lto-do options are 'assemble', 'run' and 'link'.
Additionally, these can only be used in the main file.  If
'assemble' is used, only the individual object files are
generated.  If 'link' is used, the final executable is generated
but not executed (in this case, function main() needs to exist
but it does not need to do anything).  If 'run' is used, the
final executable is generated and the resulting binary executed.

The default value for dg-lto-do is 'run'.