z80: Output jump offsets relative to instruction start.

Most assemblers recognize the symbol $ for the address of the
current instruction. Make use of this to output relative jump
instructions using the $[+-]offset syntax, with offset being
the displacement minus the instruction length.

2 files changed, 18 insertions, 13 deletions

diff --git a/decoders/z80/pd.py b/decoders/z80/pd.py
index 088408a..c88ea05 100644
--- a/decoders/z80/pd.py
+++ b/decoders/z80/pd.py
@@ -139,6 +139,7 @@ class Decoder(srd.Decoder):
         self.ann_dasm   = None
         self.prev_cycle = Cycle.NONE
         self.op_state   = OpState.IDLE
+        self.instr_len  = 0
 
     def decode(self, ss, es, data):
         for (self.samplenum, pins) in data:
@@ -175,6 +176,7 @@ class Decoder(srd.Decoder):
         self.pend_addr  = bus_addr
 
     def on_cycle_end(self):
+        self.instr_len += 1
         self.op_state = getattr(self, 'on_state_' + self.op_state)()
         if self.ann_dasm is not None:
             self.put_disasm()
@@ -196,8 +198,8 @@ class Decoder(srd.Decoder):
         self.ann_dasm  = None
 
     def put_disasm(self):
-        text = formatter.format(self.mnemonic, r=self.arg_reg,
-                                d=self.arg_dis, i=self.arg_imm,
+        text = formatter.format(self.mnemonic, r=self.arg_reg, d=self.arg_dis,
+                                j=self.arg_dis+self.instr_len, i=self.arg_imm,
                                 ro=self.arg_read, wo=self.arg_write)
         self.put_text(self.dasm_start, self.ann_dasm, text)
         self.ann_dasm   = None
@@ -226,6 +228,7 @@ class Decoder(srd.Decoder):
         self.write_pend = False
         self.dasm_start = self.samplenum
         self.op_prefix  = 0
+        self.instr_len  = 0
         if self.bus_data in (0xCB, 0xED, 0xDD, 0xFD):
             return OpState.PRE1
         else:
diff --git a/decoders/z80/tables.py b/decoders/z80/tables.py
index 3f768b2..ec77dae 100644
--- a/decoders/z80/tables.py
+++ b/decoders/z80/tables.py
@@ -24,17 +24,19 @@ Instruction tuple: (d, i, ro, wo, rep, format string)
   used for the displacement and the immediate operand, respectively. An
   operand consisting of more than one byte is assembled in little endian
   order.
-  The format string should refer to the {d} and {i} operands by name.
-  Displacements are interpreted as signed integers, whereas immediate
-  operands are always read as unsigned. The tables for instructions
-  operating on the IX/IY index registers additionally use {r} in the
-  format string as a placeholder for the register name.
   The placeholders ro and wo are the number of bytes the instruction
   is expected to read or write, respectively. These counts are used
   for both memory and I/O access, but not for immediate operands.
   A negative value indicates that the operand byte order is big endian
   rather than the usual little endian.
   The placeholder rep is a boolean used to mark repeating instructions.
+  The format string should refer to the {d} and {i} operands by name.
+  Displacements are interpreted as signed integers, whereas immediate
+  operands are always read as unsigned. The tables for instructions
+  operating on the IX/IY index registers additionally use {r} in the
+  format string as a placeholder for the register name.
+  Relative jump instructions may specify {j} instead of {d} to output
+  the displacement relative to the start of the instruction.
 '''
 
 # Instructions without a prefix
@@ -56,7 +58,7 @@ main_instructions = {
     0x0E: (0, 1, 0, 0, False, 'LD C,{i:02H}h'),
     0x0F: (0, 0, 0, 0, False, 'RRCA'),
 
-    0x10: (1, 0, 0, 0, False, 'DJNZ {d:+d}'),
+    0x10: (1, 0, 0, 0, False, 'DJNZ ${j:+d}'),
     0x11: (0, 2, 0, 0, False, 'LD DE,{i:04H}h'),
     0x12: (0, 0, 0, 1, False, 'LD (DE),A'),
     0x13: (0, 0, 0, 0, False, 'INC DE'),
@@ -64,7 +66,7 @@ main_instructions = {
     0x15: (0, 0, 0, 0, False, 'DEC D'),
     0x16: (0, 1, 0, 0, False, 'LD D,{i:02H}h'),
     0x17: (0, 0, 0, 0, False, 'RLA'),
-    0x18: (1, 0, 0, 0, False, 'JR {d:+d}'),
+    0x18: (1, 0, 0, 0, False, 'JR ${j:+d}'),
     0x19: (0, 0, 0, 0, False, 'ADD HL,DE'),
     0x1A: (0, 0, 1, 0, False, 'LD A,(DE)'),
     0x1B: (0, 0, 0, 0, False, 'DEC DE'),
@@ -73,7 +75,7 @@ main_instructions = {
     0x1E: (0, 1, 0, 0, False, 'LD E,{i:02H}h'),
     0x1F: (0, 0, 0, 0, False, 'RRA'),
 
-    0x20: (1, 0, 0, 0, False, 'JR NZ,{d:+d}'),
+    0x20: (1, 0, 0, 0, False, 'JR NZ,${j:+d}'),
     0x21: (0, 2, 0, 0, False, 'LD HL,{i:04H}h'),
     0x22: (0, 2, 0, 2, False, 'LD ({i:04H}h),HL'),
     0x23: (0, 0, 0, 0, False, 'INC HL'),
@@ -81,7 +83,7 @@ main_instructions = {
     0x25: (0, 0, 0, 0, False, 'DEC H'),
     0x26: (0, 1, 0, 0, False, 'LD H,{i:02H}h'),
     0x27: (0, 0, 0, 0, False, 'DAA'),
-    0x28: (1, 0, 0, 0, False, 'JR Z,{d:+d}'),
+    0x28: (1, 0, 0, 0, False, 'JR Z,${j:+d}'),
     0x29: (0, 0, 0, 0, False, 'ADD HL,HL'),
     0x2A: (0, 2, 2, 0, False, 'LD HL,({i:04H}h)'),
     0x2B: (0, 0, 0, 0, False, 'DEC HL'),
@@ -90,7 +92,7 @@ main_instructions = {
     0x2E: (0, 1, 0, 0, False, 'LD L,{i:02H}h'),
     0x2F: (0, 0, 0, 0, False, 'CPL'),
 
-    0x30: (1, 0, 0, 0, False, 'JR NC,{d:+d}'),
+    0x30: (1, 0, 0, 0, False, 'JR NC,${j:+d}'),
     0x31: (0, 2, 0, 0, False, 'LD SP,{i:04H}h'),
     0x32: (0, 2, 0, 1, False, 'LD ({i:04H}h),A'),
     0x33: (0, 0, 0, 0, False, 'INC SP'),
@@ -98,7 +100,7 @@ main_instructions = {
     0x35: (0, 0, 1, 1, False, 'DEC (HL)'),
     0x36: (0, 1, 0, 1, False, 'LD (HL),{i:02H}h'),
     0x37: (0, 0, 0, 0, False, 'SCF'),
-    0x38: (1, 0, 0, 0, False, 'JR C,{d:+d}'),
+    0x38: (1, 0, 0, 0, False, 'JR C,${j:+d}'),
     0x39: (0, 0, 0, 0, False, 'ADD HL,SP'),
     0x3A: (0, 2, 1, 0, False, 'LD A,({i:04H}h)'),
     0x3B: (0, 0, 0, 0, False, 'DEC SP'),