This new representation means that a valid command line option may
potentially be used directly as a multilib flag without any translation.
To indicate that a flag is required not to be present, its first
character is replaced with '!', which is intended for consistency with
the logical not operator in many programming languages.
Reviewed By: simon_tatham
Differential Revision: https://reviews.llvm.org/D151438
Decouple the interface of the MultilibBuilder flag method from how flags
are stored internally. Likewise change the addMultilibFlag function.
Currently a multilib flag like "-fexceptions" means a multilib is
*incompatible* with the -fexceptions command line option, which is
counter-intuitive. This change is a step towards changing this scheme.
Differential Revision: https://reviews.llvm.org/D151437
The new algorithm is:
1. Find all multilibs with flags that are a subset of the requested
flags.
2. If more than one multilib matches, choose the last.
In addition a new selection mechanism is permitted via an overload of
MultilibSet::select() for which multiple multilibs are returned.
This allows layering multilibs on top of each other.
Since multilibs are now ordered within a list, they no longer need a
Priority field.
The new algorithm is different to the old algorithm, but in practise
the old algorithm was always used in such a way that the effect is the
same.
The old algorithm was to find the set intersection of the requested
flags (with the first character of each removed) with each multilib's
flags (ditto), and for that intersection check whether the first
character matched. However, ignoring the first characters, the
requested flags were always a superset of all the multilibs flags.
Therefore the new algorithm can be used as a drop-in replacement.
The exception is Fuchsia, which needs adjusting slightly to set both
fexceptions and fno-exceptions flags.
Differential Revision: https://reviews.llvm.org/D142905
The functionality in MultilibSet for creating it is tied to its current
implementation. Putting that code in a separate class is an enabler for
changing the MultilibSet implementation.
Differential Revision: https://reviews.llvm.org/D142893
