support negative offsets to PlusRegister

Also sign extend in PlusRegister#to_s.
judofyr · Apr 12, 2012 · 14bf423 · 14bf423
1 parent 21dab79
commit 14bf423
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Showing 2 changed files with 16 additions and 2 deletions.
diff --git a/lib/rcpu.rb b/lib/rcpu.rb
@@ -190,6 +190,10 @@ def +(n)
       PlusRegister.new(self, n)
     end
 
+    def -(n)
+      self + -n
+    end
+
     def execute(emu)
       case name
       when *REAL
@@ -227,7 +231,13 @@ def code
 
   class PlusRegister < Struct.new(:register, :value)
     def to_s
-      "[#{register}+#{value}]"
+      v = if value.is_a? Fixnum
+        # Sign extend from 16 bits
+        value | (-value[15] & ~0xFFFF)
+      else
+        value
+      end
+      "[%s%+d]" % [register, v]
     end
 
     def code

diff --git a/test/test_emulator.rb b/test/test_emulator.rb
@@ -276,6 +276,8 @@ def test_format
         block :main do
           SET a, 1
           ADD [a], 0x1000
+          ADD [a+0xFFFF], 0x1000
+          ADD [a-2], 0x1000
           SUB [a+1], [0x10]
           SET push, o
           SET x, pop
@@ -290,12 +292,14 @@ def test_format
       res = [
         "SET a, 0x1",
         "ADD [a], 0x1000",
+        "ADD [a-1], 0x1000",
+        "ADD [a-2], 0x1000",
         "SUB [a+1], [0x10]",
         "SET push, o",
         "SET x, pop",
         "SET x, peek",
         "SET x, pc",
-        "JSR 0xC",
+        "JSR 0x12",
         "SUB pc, 0x1"
       ]