CR16 Operand Qualifiers

9.7.1 CR16 Operand Qualifiers

The National Semiconductor CR16 target of as has a few machine dependent operand qualifiers.

Operand expression type qualifier is an optional field in the instruction operand, to determines the type of the expression field of an operand. The @ is required. CR16 architecture uses one of the following expression qualifiers:

s: - Specifies expression operand type as small
m: - Specifies expression operand type as medium
l: - Specifies expression operand type as large
c: - Specifies the CR16 Assembler generates a relocation entry for the operand, where pc has implied bit, the expression is adjusted accordingly. The linker uses the relocation entry to update the operand address at link time.
got/GOT: - Specifies the CR16 Assembler generates a relocation entry for the operand, offset from Global Offset Table. The linker uses this relocation entry to update the operand address at link time
cgot/cGOT: - Specifies the CompactRISC Assembler generates a relocation entry for the operand, where pc has implied bit, the expression is adjusted accordingly. The linker uses the relocation entry to update the operand address at link time.

CR16 target operand qualifiers and its size (in bits):

‘Immediate Operand: s’: 4 bits.
‘Immediate Operand: m’: 16 bits, for movb and movw instructions.
‘Immediate Operand: m’: 20 bits, movd instructions.
‘Immediate Operand: l’: 32 bits.
‘Absolute Operand: s’: Illegal specifier for this operand.
‘Absolute Operand: m’: 20 bits, movd instructions.
‘Displacement Operand: s’: 8 bits.
‘Displacement Operand: m’: 16 bits.
‘Displacement Operand: l’: 24 bits.

For example:

     1   movw $_myfun@c,r1
     
         This loads the address of _myfun, shifted right by 1, into r1.
     
     2   movd $_myfun@c,(r2,r1)
     
         This loads the address of _myfun, shifted right by 1, into register-pair r2-r1.
     
     3   _myfun_ptr:
         .long _myfun@c
         loadd _myfun_ptr, (r1,r0)
         jal (r1,r0)
     
         This .long directive, the address of _myfunc, shifted right by 1 at link time.
     
     4   loadd  _data1@GOT(r12), (r1,r0)
     
         This loads the address of _data1, into global offset table (ie GOT) and its offset value from GOT loads into register-pair r2-r1.
     
     5   loadd  _myfunc@cGOT(r12), (r1,r0)
     
         This loads the address of _myfun, shifted right by 1, into global offset table (ie GOT) and its offset value from GOT loads into register-pair r1-r0.