mode dependent constants

[Joern Rennecke]

> I am working for gcc z80 port.
>  In z80 the valid constants range depends on the
>  instruction that involves the constants.
>   If it is an 8 bit operation, the valid range is
>        -128 to 127 and it differs in the  16 bit
> operations.
>   But in gcc I am not able to figure out how to
>  handle this. The macro LEGITIMATE_CONSTANT 
>  checks for the valid constant range. But actually if
> I say 
>    some mode dependent check, it does n't work. 
> 
>  May be because constants can pass any mode.
>   Could you please tell me how to handle this.
>  If I am assuming something wrong please let me
> know.thanks and regards
> V.Brahmaiah

LEGITIMATE_CONSTANT only says if the constant is valid for some insn.
Others might still reject it.  You should use predicates and constraints
an the different insns to specify which constants are allowed.