Certain pseudo opcodes are permitted for branch instructions. They expand to the shortest branch instruction that reach the target. Generally these mnemonics are made by prepending j to the start of Motorola mnemonic. These pseudo opcodes are not affected by the -short-branchs or -force-long-branchs options.
The following table summarizes the pseudo-operations.
Displacement Width
+-------------------------------------------------------------+
| Options |
| --short-branchs --force-long-branchs |
+--------------------------+----------------------------------+
Op |BYTE WORD | BYTE WORD |
+--------------------------+----------------------------------+
bsr | bsr <pc-rel> <error> | jsr <abs> |
bra | bra <pc-rel> <error> | jmp <abs> |
jbsr | bsr <pc-rel> jsr <abs> | bsr <pc-rel> jsr <abs> |
jbra | bra <pc-rel> jmp <abs> | bra <pc-rel> jmp <abs> |
bXX | bXX <pc-rel> <error> | bNX +3; jmp <abs> |
jbXX | bXX <pc-rel> bNX +3; | bXX <pc-rel> bNX +3; jmp <abs> |
| jmp <abs> | |
+--------------------------+----------------------------------+
XX: condition
NX: negative of condition XX
|
These are the simplest jump pseudo-operations; they always map to one particular machine instruction, depending on the displacement to the branch target.
Here, jbXX 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:
jbcc jbeq jbge jbgt jbhi jbvs jbpl jblo jbcs jbne jblt jble jbls jbvc jbmi |
For the cases of non-PC relative displacements and long displacements, as issues a longer code fragment in terms of NX, the opposite condition to XX. For example, for the non-PC relative case:
jbXX foo |
bNXs oof
jmp foo
oof: |