Implement compiling if, but we need relative addressing first.

src/sixtypical/compiler.py

@@ -7,12 +7,13 @@ from sixtypical.model import (
 )
 from sixtypical.emitter import Label, Byte
 from sixtypical.gen6502 import (
-    Immediate, Absolute,
+    Immediate, Absolute, Relative,
     LDA, LDX, LDY, STA, STX, STY,
     CLC, SEC, ADC, SBC, ROL, ROR,
-    RTS, JSR,
     INC, INX, INY, DEC, DEX, DEY,
     CMP, CPX, CPY, AND, ORA, EOR,
+    BCC, BNE,
+    JMP, JSR, RTS,
 )
 
 
@@ -58,10 +59,8 @@ class Compiler(object):
 
     def compile_block(self, block):
         assert isinstance(block, Block)
-        label = self.emitter.make_label()
         for instr in block.instrs:
             self.compile_instr(instr)
-        return label
 
     def compile_instr(self, instr):
         assert isinstance(instr, Instr)
@@ -168,6 +167,22 @@ class Compiler(object):
             label = self.labels[instr.name]
             self.emitter.emit(JSR(Absolute(label)))
         elif opcode == 'if':
-            raise NotImplementedError
+            cls = {
+                'c': BCC,
+                'z': BNE,
+            }.get(src.name)
+            if cls is None:
+                raise UnsupportedOpcodeError(instr)
+            else_label = Label('else_label')
+            self.emitter.emit(cls(Relative(else_label)))
+            self.compile_block(instr.block1)
+            if instr.block2:
+                end_label = Label('end_label')
+                self.emitter.emit(JMP(Absolute(end_label)))
+                self.emitter.resolve_label(else_label)
+                self.compile_block(instr.block2)
+                self.emitter.resolve_label(end_label)
+            else:
+                self.emitter.resolve_label(else_label)
         else:
             raise NotImplementedError

src/sixtypical/gen6502.py

@@ -8,6 +8,9 @@ class AddressingMode(object):
         """Size of the operand for the mode (not including the opcode)"""
         raise NotImplementedError
 
+    def __repr__(self):
+        return "%s(%r)" % (self.__class__.__name__, self.value)
+
 
 class Implied(AddressingMode):
     def size(self):
@@ -31,9 +34,6 @@ class Immediate(AddressingMode):
     def serialize(self):
         return self.value.serialize()
 
-    def __repr__(self):
-        return "%s(%r)" % (self.__class__.__name__, self.value)
-
 
 class Absolute(AddressingMode):
     def __init__(self, value):
@@ -46,8 +46,18 @@ class Absolute(AddressingMode):
     def serialize(self):
         return self.value.serialize()
 
-    def __repr__(self):
-        return "%s(%r)" % (self.__class__.__name__, self.value)
+
+class Relative(AddressingMode):
+    def __init__(self, value):
+        assert isinstance(value, (Byte, Label))
+        self.value = value
+
+    def size(self):
+        return 1
+
+    def serialize(self):
+        # HA
+        return chr(0xff)
 
 
 class Opcode(Emittable):
@@ -81,6 +91,18 @@ class AND(Opcode):
     }
 
 
+class BCC(Opcode):
+    opcodes = {
+        Relative:  0x90,
+    }
+
+
+class BNE(Opcode):
+    opcodes = {
+        Relative:  0xd0,
+    }
+
+
 class CLC(Opcode):
     opcodes = {
         Implied:   0x18
@@ -151,6 +173,12 @@ class INY(Opcode):
     }
 
 
+class JMP(Opcode):
+    opcodes = {
+        Absolute:  0x4c,
+    }
+
+
 class JSR(Opcode):
     opcodes = {
         Absolute:  0x20,

tests/SixtyPical Compilation.md

@@ -118,3 +118,17 @@ Some instructions.
     |     shr a
     | }
     = 00c0a900a200a0008d46c08e46c08c46c0381869016d46c0e901ed46c0ee46c0e8c8ce46c0ca8829ff2d46c009ff0d46c049ff4d46c0c901cd46c0e001ec46c0c001cc46c02a6a60
+
+Compiling `if`.
+
+    | routine main
+    |   trashes a, x, y, z, n, c, v
+    | {
+    |     ld a, 0
+    |     if z {
+    |         ld y, 1
+    |     } else {
+    |         ld y, 2
+    |     }
+    | }
+    = 00c0