The GCC manual says that
``Eventually there may be a way of asking the compiler to choose a register
automatacally...''
Would it be possible to implement it? My idea is: add a builtin function
__builtin_choose_register(HINTS)
with the property
a) it is special in that the return value is ``constant enough'' to be used in
a ``register TYPE foo asm()'' (preprocessor expansion?)
b) it looks for a register
c) it honors the HINTS argument (more on this later in this message)
On the part of the machine description, there would be a macro,
BUILTIN_CHOOSE_REG(HINTS) that returns a string containing what __builtin_
choose_register would return.
The HINTS argument would be a bitmask contisting of the following bits:
01 Use a register normally used for global variables.
02 Use highest register number possible (on CISC archs highest letter)
04 As last resort use memory
etc Other bits are arch-dependant
Samuel Lauber
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