GNU Info

(as.info)V850 Opcodes

---

Prev: V850 Directives Up: V850-Dependent

---

Enter node , (file) or (file)node

Opcodes
-------

   `as' implements all the standard V850 opcodes.

   `as' also implements the following pseudo ops:

`hi0()'
     Computes the higher 16 bits of the given expression and stores it
     into the immediate operand field of the given instruction.  For
     example:

     `mulhi hi0(here - there), r5, r6'

     computes the difference between the address of labels 'here' and
     'there', takes the upper 16 bits of this difference, shifts it
     down 16 bits and then mutliplies it by the lower 16 bits in
     register 5, putting the result into register 6.

`lo()'
     Computes the lower 16 bits of the given expression and stores it
     into the immediate operand field of the given instruction.  For
     example:

     `addi lo(here - there), r5, r6'

     computes the difference between the address of labels 'here' and
     'there', takes the lower 16 bits of this difference and adds it to
     register 5, putting the result into register 6.

`hi()'
     Computes the higher 16 bits of the given expression and then adds
     the value of the most significant bit of the lower 16 bits of the
     expression and stores the result into the immediate operand field
     of the given instruction.  For example the following code can be
     used to compute the address of the label 'here' and store it into
     register 6:

     `movhi hi(here), r0, r6'     `movea lo(here), r6, r6'

     The reason for this special behaviour is that movea performs a sign
     extention on its immediate operand.  So for example if the address
     of 'here' was 0xFFFFFFFF then without the special behaviour of the
     hi() pseudo-op the movhi instruction would put 0xFFFF0000 into r6,
     then the movea instruction would takes its immediate operand,
     0xFFFF, sign extend it to 32 bits, 0xFFFFFFFF, and then add it
     into r6 giving 0xFFFEFFFF which is wrong (the fifth nibble is E).
     With the hi() pseudo op adding in the top bit of the lo() pseudo
     op, the movhi instruction actually stores 0 into r6 (0xFFFF + 1 =
     0x0000), so that the movea instruction stores 0xFFFFFFFF into r6 -
     the right value.

`hilo()'
     Computes the 32 bit value of the given expression and stores it
     into the immediate operand field of the given instruction (which
     must be a mov instruction).  For example:

     `mov hilo(here), r6'

     computes the absolute address of label 'here' and puts the result
     into register 6.

`sdaoff()'
     Computes the offset of the named variable from the start of the
     Small Data Area (whoes address is held in register 4, the GP
     register) and stores the result as a 16 bit signed value in the
     immediate operand field of the given instruction.  For example:

     `ld.w sdaoff(_a_variable)[gp],r6'

     loads the contents of the location pointed to by the label
     '_a_variable' into register 6, provided that the label is located
     somewhere within +/- 32K of the address held in the GP register.
     [Note the linker assumes that the GP register contains a fixed
     address set to the address of the label called '__gp'.  This can
     either be set up automatically by the linker, or specifically set
     by using the `--defsym __gp=<value>' command line option].

`tdaoff()'
     Computes the offset of the named variable from the start of the
     Tiny Data Area (whoes address is held in register 30, the EP
     register) and stores the result as a 4,5, 7 or 8 bit unsigned
     value in the immediate operand field of the given instruction.
     For example:

     `sld.w tdaoff(_a_variable)[ep],r6'

     loads the contents of the location pointed to by the label
     '_a_variable' into register 6, provided that the label is located
     somewhere within +256 bytes of the address held in the EP
     register.  [Note the linker assumes that the EP register contains
     a fixed address set to the address of the label called '__ep'.
     This can either be set up automatically by the linker, or
     specifically set by using the `--defsym __ep=<value>' command line
     option].

`zdaoff()'
     Computes the offset of the named variable from address 0 and
     stores the result as a 16 bit signed value in the immediate
     operand field of the given instruction.  For example:

     `movea zdaoff(_a_variable),zero,r6'

     puts the address of the label '_a_variable' into register 6,
     assuming that the label is somewhere within the first 32K of
     memory.  (Strictly speaking it also possible to access the last
     32K of memory as well, as the offsets are signed).

`ctoff()'
     Computes the offset of the named variable from the start of the
     Call Table Area (whoes address is helg in system register 20, the
     CTBP register) and stores the result a 6 or 16 bit unsigned value
     in the immediate field of then given instruction or piece of data.
     For example:

     `callt ctoff(table_func1)'

     will put the call the function whoes address is held in the call
     table at the location labeled 'table_func1'.

   For information on the V850 instruction set, see `V850 Family
32-/16-Bit single-Chip Microcontroller Architecture Manual' from NEC.
Ltd.