Problem with instruction description

[youssef fahmi <yflelion at hotmail dot fr>]

Hello,
I'm sorry for the previous mail, I do not know why there were "Â" everywhere.
I am working on the porting of binutils to a new architecture.This processor has an instruction of the form: ld rx,[r1] + imm6?[load the 32 bit word at the address calculated from the contents?of r1 plus the 6 bit immediate value (multiplied by 4) ]In summary: rx <- mem[r1 + imm6 * 4]
I need to generate code for this instruction, but only in the case?where the code generator in the compiler generates a standard load,?but with an offset appropriate for the imm6 value.?That is to say the immediate value would be less than?256 and be a multiple of 4 (word access).
This is the description that I am using at the moment:(df f-imm6x4 "imm6x4" ()? 11 6 UINT? ((value pc) (sra WI value (const 2)))? ((value pc) (sll WI value (const 2))))(dnop imm6x4 "imm6x4" () h-uint f-imm6x4)(dni ldstack-r1-imm6x4 "ldstack r1#imm6x4" ???() ???"ld $r1,[r1]+$imm6x4"?(+ (f-stack-opcode #05) r1 imm6x4)??() ???()) ??However this description causes the "ld rx,[r1] + imm6" to be used?whenever the immediate vallue is less than 256, and not JUST when?the offset is also a multiple of 4.
How do I alter this description so that it only operates when the?immediate value is less than 256 AND ALSO a multiple of 4.
I have already tried.... but this generates code with this instruction?in these cases which are not appropriate.How do I achieve this??I guess that I'll have to create an attribute to handle this, but I could?not get an attribute that suits me.?is there a way to create an attribute of type integer, for example, but with?only specific integers not necessarily following. ?
Thanks in advance ?for your answer.Youssef?