[NEW] ignore most whitespace. Fixed division (use cdq before idiv).

compiler.rb

@@ -17,18 +17,19 @@ class Compiler
     @data = ''                   # data section
     @bss = ''                    # bss section
     @code = ''                   # code section
+    @vars = {}
 
     # seed the lexer
     get_char
+    skip_whitespace
   end
 
   def parse
-    statement
+    statement until eof?
-    expression; newline
     [@data, @bss, @code]
   end
 
-  # Read the next character from the input stream
+  # Read the next character from the input stream.
   def get_char
     @look = if @input.eof?
               nil
@@ -51,14 +52,7 @@ class Compiler
     end
   end
   
-  # Match a specific input character
+
-  def match(char)
-    if @look == char
-      get_char
-    else
-      expected("'#{char}'")
-    end
-  end
 
   # Recognize an alphabetical character.
   def alpha?(char)
@@ -75,28 +69,48 @@ class Compiler
     alpha?(char) || digit?(char)
   end
 
-  # Get an identifier.
+  def whitespace?(char)
-  def get_name
+    char == ' ' || char == '\t'
-    expected('identifier') unless alpha?(@look)
+  end
+
+
+  # Match a specific input character.
+  def match(char)
+    expected("'#{char}'") unless @look == char
+    get_char
+    skip_whitespace
+  end
+
+  # Parse zero or more consecutive characters for which the test is
+  # true.
+  def many(test)
     token = ''
-    while alnum?(@look)
+    while test.call(@look)
       token << @look
       get_char
     end
+    skip_whitespace
     token
   end
 
+  # Get an identifier.
+  def get_name
+    expected('identifier') unless alpha?(@look)
+    many(method(:alnum?))
+  end
+
   # Get a number.
   def get_num
     expected('integer') unless digit?(@look)
-    value = ''
+    many(method(:digit?))
-    while digit?(@look)
-      value << @look
-      get_char
-    end
-    value
   end
 
+  # Skip all leading whitespace.
+  def skip_whitespace
+    get_char while whitespace?(@look)
+  end
+
+
   # Define a constant in the .data section.
   def equ(name, value)
     @data << "#{name}\tequ  #{value}"
@@ -104,7 +118,12 @@ class Compiler
 
   # Define a variable with the given name and size (in dwords).
   def var(name, dwords=1)
-    @bss << "#{name}: resd #{dwords}\n"
+    unless @vars[name]
+      @bss << "#{name}: resd #{dwords}\n"
+      @vars[name] = name
+    # else
+    #   raise ParseError, "identifier #{name} redefined"
+    end
   end
 
   # Emit a line of code wrapped between a tab and a newline.
@@ -112,6 +131,8 @@ class Compiler
     @code << "\t#{s}\n"
   end
 
+
+
   # Parse and translate an identifier or function call.
   def identifier
     name = get_name
@@ -120,10 +141,10 @@ class Compiler
       # function call
       match('(')
       match(')')
-      call(name)
+      x86_call(name)
     else
       # variable access
-      mov("eax", "dword [#{name}]")
+      x86_mov(:eax, "dword [#{name}]")
     end
   end
 
@@ -137,7 +158,7 @@ class Compiler
     when alpha?(@look)
       identifier
     when digit?(@look)
-      mov("eax", get_num)
+      x86_mov(:eax, get_num)
     else
       expected("a number, identifier, or an expression wrapped in parens")
     end
@@ -152,7 +173,7 @@ class Compiler
       # multiply & divide.  Because they leave their results in eax
       # associativity works.  Each interim result is pushed on the
       # stack here.
-      push("eax")
+      x86_push(:eax)
 
       if @look == '*'
         multiply
@@ -160,7 +181,7 @@ class Compiler
         divide
       end
 
-      add("esp", 4)        # Remove the 1st factor from the stack.
+      x86_add(:esp, 4)        # Remove the 1st factor from the stack.
     end
   end
 
@@ -170,7 +191,7 @@ class Compiler
     if addop?
       # Clear eax simulating a zero before unary plus and minus
       # operations.
-      xor("eax", "eax")
+      x86_xor(:eax, :eax)
     else
       term                      # Result is in eax.
     end
@@ -180,7 +201,7 @@ class Compiler
       # subtract.  Because they leave their results in eax
       # associativity works.  Each interim result is pushed on the
       # stack here.
-      push("eax")
+      x86_push(:eax)
 
       if @look == '+'
         add
@@ -188,7 +209,7 @@ class Compiler
         subtract
       end
 
-      add("esp", 4)        # Remove 1st term (a) from the stack.
+      x86_add(:esp, 4)        # Remove 1st term (a) from the stack.
     end
   end
 
@@ -198,7 +219,7 @@ class Compiler
     match('=')
     expression
     var(name)
-    mov("dword [#{name}]", "eax")
+    x86_mov("dword [#{name}]", :eax)
   end
 
   # Parse one or more newlines.
@@ -222,7 +243,7 @@ class Compiler
   def add
     match('+')
     term                        # Result is in eax.
-    add('eax', '[esp]')         # Add a to b.
+    x86_add(:eax, '[esp]')         # Add a to b.
   end
 
   # Parse a subtraction operator and the 2nd term (b).  The result is
@@ -230,8 +251,8 @@ class Compiler
   def subtract
     match('-')
     term                      # Result is in eax.
-    sub('eax', '[esp]')       # Subtract a from b (this is backwards).
+    x86_sub(:eax, '[esp]')       # Subtract a from b (this is backwards).
-    neg('eax')                # Fix things up.  -(b-a) == a-b
+    x86_neg(:eax)                # Fix things up.  -(b-a) == a-b
   end
 
   # Parse an addition operator and the 2nd term (b).  The result is
@@ -239,7 +260,7 @@ class Compiler
   def multiply
     match('*')
     factor                      # Result is in eax.
-    imul('dword [esp]')         # Multiply a by b.
+    x86_imul('dword [esp]')     # Multiply a by b.
   end
 
   # Parse a division operator and the divisor (b).  The result is
@@ -247,9 +268,14 @@ class Compiler
   def divide
     match('/')
     factor                      # Result is in eax.
-    xchg('eax', '[esp]')        # Swap the divisor and dividend into
+    x86_xchg(:eax, '[esp]')     # Swap the divisor and dividend into
                                 # the correct places.
-    idiv('dword [esp]')         # Divide a (eax) by b ([esp]).
+
+    # idiv uses edx:eax as the dividend so we need to ensure that edx
+    # is correctly sign-extended w.r.t. eax.
+    emit('cdq')       # Sign-extend eax into edx (Convert Double to
+                      # Quad).
+    x86_idiv('dword [esp]')     # Divide a (eax) by b ([esp]).
   end
 
 
@@ -273,39 +299,43 @@ private
 
   # Some asm methods for convenience and arity checks.
 
-  def mov(dest, src)
+  def x86_mov(dest, src)
     emit("mov #{dest}, #{src}")
   end
 
-  def add(dest, src)
+  def x86_add(dest, src)
     emit("add #{dest}, #{src}")
   end
 
-  def sub(dest, src)
+  def x86_sub(dest, src)
     emit("sub #{dest}, #{src}")
   end
 
-  def imul(op)
+  def x86_imul(op)
     emit("imul #{op}")
   end
 
-  def idiv(op)
+  def x86_idiv(op)
     emit("idiv #{op}")
   end
 
-  def push(reg)
+  def x86_push(reg)
     emit("push #{reg}")
   end
 
-  def call(label)
+  def x86_call(label)
     emit("call #{label}")
   end
 
-  def neg(reg)
+  def x86_neg(reg)
     emit("neg #{reg}")
   end
 
-  def xchg(op1, op2)
+  def x86_xchg(op1, op2)
     emit("xchg #{op1}, #{op2}")
   end
+
+  def x86_xor(op1, op2)
+    emit("xor #{op1}, #{op2}")
+  end
 end

test.code

@@ -1,5 +1,11 @@
 a=9
-5*(3-5)*2+2-9/3-8/2-4*(5+5+5)
+aa=10
-a-1
+somethinglong=65536
-x()+1
+b=5*(3-5)
--1
+c=a-1
+d=-1
+e=b*2+2
+f=e-27/9
+g=f-8/2
+h=g-4*(5+5+5)
+i=h+85