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Re: readonly register
BELBACHIR Selim <email@example.com> writes:
> I'm trying to support an 'in' instruction which reads a value on a peripheral and writes it into a $INP register.
> The $INP register can be used in almost every insn as input operand (add, sub, mul ...).
> I defined a builting to access the 'in' instruction.
> How should I express to gcc that the $INP register can only be 'read' and must never be written?
> For the moment, I encounter a problem during IRA pass where some of my 'classic' registers are reloaded into $INP (apparently because I have no register left).
If you have a builtin to access the value, then you should be able to
make it a fixed register. The register allocator will never try to
allocate a fixed register.