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add relative labels a la asw

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This commit is contained in:
Connor Olding 2016-01-05 01:10:52 -08:00
parent 7a0aac3b7c
commit 59d4de30fa
1 changed files with 58 additions and 8 deletions
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66
lips.lua
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@ -788,13 +788,20 @@ function Lexer:lex(_yield)
self:error('unmatched closing bracket')
elseif self.chr == ')' then
self:error('unmatched closing parenthesis')
elseif self.chr == '-' then
self:nextc()
local n = self:read_number()
if n then
yield('NUM', -n)
elseif self.chr == '+' or self.chr == '-' then
local sign_chr = self.chr
local sign = sign_chr == '+' and 1 or -1
local buff = self:read_chars('%'..self.chr)
if #buff == 1 and self.chr == ':' then
self:nextc()
yield('RELLABEL', sign_chr)
else
self:error('expected number after minus sign')
local n = self:read_number()
if n then
yield('NUM', sign*n)
else
yield('RELLABELSYM', sign*#buff)
end
end
else
local n = self:read_number()
@ -1404,12 +1411,14 @@ function Parser:tokenize(asm)
return t.tt, t.tok, t.fn, t.line
end
-- first pass: collect tokens and constants.
-- first pass: collect tokens, constants, and relative labels.
-- can't do more because instruction size can depend on a constant's size
-- and labels depend on instruction size.
-- note however, instruction size does not depend on label size.
-- this would cause a recursive problem to solve,
-- which is too much for our simple assembler.
local plus_labels = {} -- constructed forwards
local minus_labels = {} -- constructed backwards
while true do
local tt, tok, fn, line = lex()
self.fn = fn
@ -1420,6 +1429,14 @@ function Parser:tokenize(asm)
self:error('expected number for define')
end
self.defines[tok] = tok2
elseif tt == 'RELLABEL' then
if tok == '+' then
insert(plus_labels, #self.tokens)
elseif tok == '-' then
insert(minus_labels, 1, #self.tokens)
else
error('Internal Error: unexpected token for relative label', 1)
end
elseif tt == 'EOL' then
-- noop
elseif tt == 'EOF' then
@ -1431,7 +1448,7 @@ function Parser:tokenize(asm)
end
end
-- resolve defines
-- resolve defines and relative labels
for i, t in ipairs(self.tokens) do
self.fn = t.fn
self.line = t.line
@ -1441,6 +1458,39 @@ function Parser:tokenize(asm)
if t.tok == nil then
self:error('undefined define') -- uhhh nice wording
end
elseif t.tt == 'RELLABEL' then
t.tt = 'LABEL'
-- exploits the fact that user labels can't begin with a number
t.tok = tostring(i)
elseif t.tt == 'RELLABELSYM' then
t.tt = 'LABELSYM'
local rel = t.tok
local seen = 0
-- TODO: don't iterate over *every* label, just the ones nearby
if rel > 0 then
for _, label_i in ipairs(plus_labels) do
if label_i > i then
seen = seen + 1
if seen == rel then
t.tok = tostring(label_i)
break
end
end
end
else
for _, label_i in ipairs(minus_labels) do
if label_i < i then
seen = seen - 1
if seen == rel then
t.tok = tostring(label_i)
break
end
end
end
end
if seen ~= rel then
self:error('could not find appropriate relative label')
end
end
end
end