Subversion Repositories openrisc_me

@c Copyright 2007, 2008 Free Software Foundation, Inc.

@c This is part of the GAS manual.

@c For copying conditions, see the file as.texinfo.

@ifset GENERIC

@page

@node CR16-Dependent

@chapter CR16 Dependent Features

@end ifset

@ifclear GENERIC

@node Machine Dependencies

@chapter CR16 Dependent Features

@end ifclear

@cindex CR16 support

@menu

* CR16 Operand Qualifiers::     CR16 Machine Operand Qualifiers

@end menu

@node CR16 Operand Qualifiers

@section CR16 Operand Qualifiers

@cindex CR16 Operand Qualifiers

The National Semiconductor CR16 target of @code{@value{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 @code{@@} is required. CR16 architecture uses one of the following expression qualifiers:

@table @code

@item  s

- @code{Specifies expression operand type as small}

@item  m

- @code{Specifies expression operand type as medium}

@item  l

- @code{Specifies expression operand type as large}

@item  c

- @code{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.}

@item  got/GOT

- @code{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}

@item  cgot/cGOT

- @code{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.}

@end table

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

@table @samp

@item Immediate Operand

- s ---- 4 bits

@item

- m ---- 16 bits, for movb and movw instructions.

@item

- m ---- 20 bits, movd instructions.

@item

- l ---- 32 bits

@item Absolute Operand

- s ---- Illegal specifier for this operand.

@item

- m ---- 20 bits, movd instructions.

@item Displacement Operand

- s ---- 8 bits

@item

- m ---- 16 bits

@item

- l ---- 24 bits

@end table

For example:

@example

1   @code{movw $_myfun@@c,r1}

    This loads the address of _myfun, shifted right by 1, into r1.

2   @code{movd $_myfun@@c,(r2,r1)}

    This loads the address of _myfun, shifted right by 1, into register-pair r2-r1.

3   @code{_myfun_ptr:}

    @code{.long _myfun@@c}

    @code{loadd _myfun_ptr, (r1,r0)}

    @code{jal (r1,r0)}

    This .long directive, the address of _myfunc, shifted right by 1 at link time.

4   @code{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   @code{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.

@end example