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[NEW] ignore most whitespace. Fixed division (use cdq before idiv).
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sjs
parent
c008ed007a
commit
bd0408fa2f
2 changed files with 86 additions and 50 deletions
122
compiler.rb
122
compiler.rb
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@ -17,18 +17,19 @@ class Compiler
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@data = '' # data section
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@bss = '' # bss section
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@code = '' # code section
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@vars = {}
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# seed the lexer
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get_char
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skip_whitespace
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end
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def parse
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statement
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expression; newline
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statement until eof?
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[@data, @bss, @code]
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end
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# Read the next character from the input stream
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# Read the next character from the input stream.
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def get_char
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@look = if @input.eof?
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nil
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@ -51,14 +52,7 @@ class Compiler
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end
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end
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# Match a specific input character
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def match(char)
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if @look == char
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get_char
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else
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expected("'#{char}'")
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end
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end
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# Recognize an alphabetical character.
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def alpha?(char)
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@ -75,28 +69,48 @@ class Compiler
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alpha?(char) || digit?(char)
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end
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# Get an identifier.
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def get_name
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expected('identifier') unless alpha?(@look)
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def whitespace?(char)
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char == ' ' || char == '\t'
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end
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# Match a specific input character.
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def match(char)
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expected("'#{char}'") unless @look == char
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get_char
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skip_whitespace
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end
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# Parse zero or more consecutive characters for which the test is
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# true.
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def many(test)
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token = ''
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while alnum?(@look)
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while test.call(@look)
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token << @look
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get_char
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end
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skip_whitespace
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token
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end
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# Get an identifier.
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def get_name
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expected('identifier') unless alpha?(@look)
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many(method(:alnum?))
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end
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# Get a number.
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def get_num
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expected('integer') unless digit?(@look)
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value = ''
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while digit?(@look)
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value << @look
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get_char
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end
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value
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many(method(:digit?))
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end
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# Skip all leading whitespace.
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def skip_whitespace
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get_char while whitespace?(@look)
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end
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# Define a constant in the .data section.
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def equ(name, value)
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@data << "#{name}\tequ #{value}"
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@ -104,7 +118,12 @@ class Compiler
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# Define a variable with the given name and size (in dwords).
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def var(name, dwords=1)
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@bss << "#{name}: resd #{dwords}\n"
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unless @vars[name]
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@bss << "#{name}: resd #{dwords}\n"
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@vars[name] = name
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# else
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# raise ParseError, "identifier #{name} redefined"
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end
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end
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# Emit a line of code wrapped between a tab and a newline.
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@ -112,6 +131,8 @@ class Compiler
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@code << "\t#{s}\n"
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end
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# Parse and translate an identifier or function call.
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def identifier
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name = get_name
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@ -120,10 +141,10 @@ class Compiler
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# function call
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match('(')
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match(')')
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call(name)
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x86_call(name)
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else
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# variable access
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mov("eax", "dword [#{name}]")
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x86_mov(:eax, "dword [#{name}]")
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end
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end
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@ -137,7 +158,7 @@ class Compiler
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when alpha?(@look)
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identifier
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when digit?(@look)
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mov("eax", get_num)
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x86_mov(:eax, get_num)
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else
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expected("a number, identifier, or an expression wrapped in parens")
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end
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@ -152,7 +173,7 @@ class Compiler
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# multiply & divide. Because they leave their results in eax
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# associativity works. Each interim result is pushed on the
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# stack here.
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push("eax")
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x86_push(:eax)
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if @look == '*'
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multiply
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@ -160,7 +181,7 @@ class Compiler
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divide
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end
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add("esp", 4) # Remove the 1st factor from the stack.
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x86_add(:esp, 4) # Remove the 1st factor from the stack.
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end
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end
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@ -170,7 +191,7 @@ class Compiler
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if addop?
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# Clear eax simulating a zero before unary plus and minus
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# operations.
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xor("eax", "eax")
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x86_xor(:eax, :eax)
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else
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term # Result is in eax.
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end
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@ -180,7 +201,7 @@ class Compiler
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# subtract. Because they leave their results in eax
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# associativity works. Each interim result is pushed on the
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# stack here.
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push("eax")
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x86_push(:eax)
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if @look == '+'
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add
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@ -188,7 +209,7 @@ class Compiler
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subtract
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end
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add("esp", 4) # Remove 1st term (a) from the stack.
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x86_add(:esp, 4) # Remove 1st term (a) from the stack.
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end
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end
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@ -198,7 +219,7 @@ class Compiler
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match('=')
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expression
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var(name)
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mov("dword [#{name}]", "eax")
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x86_mov("dword [#{name}]", :eax)
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end
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# Parse one or more newlines.
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@ -222,7 +243,7 @@ class Compiler
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def add
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match('+')
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term # Result is in eax.
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add('eax', '[esp]') # Add a to b.
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x86_add(:eax, '[esp]') # Add a to b.
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end
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# Parse a subtraction operator and the 2nd term (b). The result is
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@ -230,8 +251,8 @@ class Compiler
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def subtract
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match('-')
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term # Result is in eax.
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sub('eax', '[esp]') # Subtract a from b (this is backwards).
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neg('eax') # Fix things up. -(b-a) == a-b
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x86_sub(:eax, '[esp]') # Subtract a from b (this is backwards).
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x86_neg(:eax) # Fix things up. -(b-a) == a-b
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end
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# Parse an addition operator and the 2nd term (b). The result is
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@ -239,7 +260,7 @@ class Compiler
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def multiply
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match('*')
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factor # Result is in eax.
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imul('dword [esp]') # Multiply a by b.
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x86_imul('dword [esp]') # Multiply a by b.
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end
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# Parse a division operator and the divisor (b). The result is
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@ -247,9 +268,14 @@ class Compiler
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def divide
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match('/')
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factor # Result is in eax.
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xchg('eax', '[esp]') # Swap the divisor and dividend into
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x86_xchg(:eax, '[esp]') # Swap the divisor and dividend into
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# the correct places.
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idiv('dword [esp]') # Divide a (eax) by b ([esp]).
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# idiv uses edx:eax as the dividend so we need to ensure that edx
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# is correctly sign-extended w.r.t. eax.
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emit('cdq') # Sign-extend eax into edx (Convert Double to
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# Quad).
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x86_idiv('dword [esp]') # Divide a (eax) by b ([esp]).
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end
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@ -273,39 +299,43 @@ private
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# Some asm methods for convenience and arity checks.
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def mov(dest, src)
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def x86_mov(dest, src)
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emit("mov #{dest}, #{src}")
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end
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def add(dest, src)
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def x86_add(dest, src)
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emit("add #{dest}, #{src}")
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end
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def sub(dest, src)
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def x86_sub(dest, src)
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emit("sub #{dest}, #{src}")
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end
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def imul(op)
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def x86_imul(op)
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emit("imul #{op}")
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end
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def idiv(op)
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def x86_idiv(op)
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emit("idiv #{op}")
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end
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def push(reg)
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def x86_push(reg)
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emit("push #{reg}")
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end
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def call(label)
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def x86_call(label)
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emit("call #{label}")
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end
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def neg(reg)
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def x86_neg(reg)
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emit("neg #{reg}")
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end
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def xchg(op1, op2)
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def x86_xchg(op1, op2)
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emit("xchg #{op1}, #{op2}")
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end
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def x86_xor(op1, op2)
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emit("xor #{op1}, #{op2}")
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end
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end
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14
test.code
14
test.code
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@ -1,5 +1,11 @@
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a=9
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5*(3-5)*2+2-9/3-8/2-4*(5+5+5)
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a-1
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x()+1
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-1
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aa=10
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somethinglong=65536
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b=5*(3-5)
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c=a-1
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d=-1
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e=b*2+2
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f=e-27/9
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g=f-8/2
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h=g-4*(5+5+5)
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i=h+85
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