The following macros control mode switching optimizations:
For an example, the SH4 can perform both single and double precision
floating point operations, but to perform a single precision operation,
the FPSCR PR bit has to be cleared, while for a double precision
operation, this bit has to be set. Changing the PR bit requires a general
purpose register as a scratch register, hence these FPSCR sets have to
be inserted before reload, i.e. you can't put this into instruction emitting
You can have multiple entities that are mode-switched, and select at run time
which entities actually need it.
return nonzero for any entity that needs mode-switching.
If you define this macro, you also have to define
NORMAL_MODE is optional.
OPTIMIZE_MODE_SWITCHING, you have to define this as initializer for an array of integers. Each initializer element N refers to an entity that needs mode switching, and specifies the number of different modes that might need to be set for this entity. The position of the initializer in the initializer - starting counting at zero - determines the integer that is used to refer to the mode-switched entity in question. In macros that take mode arguments / yield a mode result, modes are represented as numbers 0 ... N - 1. N is used to specify that no mode switch is needed / supplied.
OPTIMIZE_MODE_SWITCHINGis defined, you must define this macro to return an integer value not larger than the corresponding element in
NUM_MODES_FOR_MODE_SWITCHING, to denote the mode that entity must be switched into prior to the execution of insn.
] - 1the lowest. The value of the macro should be an integer designating a mode for entity. For any fixed entity,
mode_priority_to_mode(entity, n) shall be a bijection in 0 ...
] - 1.