Chapter 26. M680x0 Dependent Features
157
|
68020
68000/10, not PC relative OK
Pseudo Op |BYTE
WORD
LONG
ABSOLUTE LONG JUMP
**
+                                                            
jbsr |bsrs
bsrw
bsrl
jsr
jra |bras
braw
bral
jmp
*
jXX |bXXs
bXXw
bXXl
bNXs;jmp
*
dbXX | N/A
dbXXw
dbXX;bras;bral
dbXX;bras;jmp
fjXX | N/A
fbXXw
fbXXl
N/A
XX: condition
NX: negative of condition XX
*
  see full description below
**
  this expansion mode is disallowed by
 pcrel
jbsr
jra
These are the simplest jump pseudo operations; they always map to one particular machine in 
struction, depending on the displacement to the branch target. This instruction will be a byte or
word branch is that is sufficient. Otherwise, a long branch will be emitted if available. If no long
branches are available and the
 pcrel
option is not given, an absolute long jump will be emitted
instead. If no long branches are available, the
 pcrel
option is given, and a word branch cannot
reach the target, an error message is generated.
In addition to standard branch operands,
as
allows these pseudo operations to have all operands
that are allowed for jsr and jmp, substituting these instructions if the operand given is not valid
for a branch instruction.
jXX
Here,
jXX
stands for an entire family of pseudo operations, where
XX
is a conditional branch or
condition code test. The full list of pseudo ops in this family is:
jhi
jls
jcc
jcs
jne
jeq
jvc
jvs
jpl
jmi
jge
jlt
jgt
jle
Usually, each of these pseudo operations expands to a single branch instruction. However, if a
word branch is not sufficient, no long branches are available, and the
 pcrel
option is not given,
as
issues a longer code fragment in terms of
NX
, the opposite condition to
XX
. For example, under
these conditions:
jXX foo
gives
bNXs oof
jmp foo
oof:
dbXX
The full family of pseudo operations covered here is
dbhi
dbls
dbcc
dbcs
dbne
dbeq
dbvc
dbvs
dbpl
dbmi
dbge
dblt
dbgt
dble
dbf
dbra
dbt
Motorola
dbXX
instructions allow word displacements only. When a word displacement is suffi 
cient, each of these pseudo operations expands to the corresponding Motorola instruction. When
a word displacement is not sufficient and long branches are available, when the source reads
dbXX foo
,
as
emits
dbXX oo1
bras oo2
oo1:bral foo
oo2:






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