From 5e3f4c7d6e6944142d6d178de41c3c191b7b89ea Mon Sep 17 00:00:00 2001
From: inglorion <voodoo@inglorion.net>
Date: Mon, 12 Jul 2010 22:02:54 +0200
Subject: [PATCH] Added support for at-expressions to i386 and AMD64 targets.

---
 lib/voodoo/generators/nasm_generator.rb | 30 ++++++++++++++++++++++++++++++
 lib/voodoo/parser.rb                    | 17 ++++++++++++++++-
 test/Makefile                           |  4 ++--
 test/test                               |  2 ++
 4 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/lib/voodoo/generators/nasm_generator.rb b/lib/voodoo/generators/nasm_generator.rb
index 9c0754c..3213299 100644
--- a/lib/voodoo/generators/nasm_generator.rb
+++ b/lib/voodoo/generators/nasm_generator.rb
@@ -185,6 +185,11 @@ module Voodoo
     # == Value Classification
     #
 
+    # Test if a value is an at-expression
+    def at_expr? value
+      value.respond_to?(:[]) && value[0] == :'@'
+    end
+
     # Test if op is a binary operation
     def binop? op
       [:div, :mod, :sub].member?(op) || symmetric_operation?(op)
@@ -271,6 +276,17 @@ module Voodoo
       end
     end
 
+    # Load the value at the given address.
+    # Invoking this code may clobber @BX.
+    def load_at address, reg = @SCRATCH_REG
+      if integer?(address) || global?(address)
+        "[#{address}]"
+      else
+        load_value_into_register address, @BX
+        "[#{@BX}]"
+      end
+    end
+
     # Load the value associated with the given symbol.
     # Returns a string that can be used to refer to the loaded value.
     def load_symbol symbol, reg = @SCRATCH_REG
@@ -298,6 +314,20 @@ module Voodoo
         value
       elsif symbol? value
         load_symbol value, reg
+      elsif at_expr? value
+        load_at value[1], reg
+      else
+        raise "Don't know how to load #{value.inspect}"
+      end
+    end
+
+    # Load a value into a register.
+    def load_value_into_register value, register
+      load_code = load_value(value), register
+      if load_code == register.to_s
+        load_code
+      else
+        "mov #{register}, #{load_code}\n"
       end
     end
 
diff --git a/lib/voodoo/parser.rb b/lib/voodoo/parser.rb
index 0e582d7..d2baaeb 100644
--- a/lib/voodoo/parser.rb
+++ b/lib/voodoo/parser.rb
@@ -108,8 +108,23 @@ module Voodoo
         when /\s/
           # Skip whitespace
           consume
+        when '@'
+          # Parse at-expression.
+          # '@' must be followed by a number or symbol.
+          consume
+          case lookahead
+          when /\d|-/
+            expr = parse_number
+          when /\w|\\/
+            expr = parse_symbol
+          else
+            raise "Invalid character (#{@lookahead.chr.inspect})" +
+              " at #{@line}:#{@char}; expecting number or symbol"
+          end
+          words << [:'@', expr]
         else
-          raise "Invalid character (#{@lookahead}) at #{@line}:#{@char}"
+          raise "Invalid character (#{@lookahead.chr.inspect})" +
+            " at #{@line}:#{@char}"
         end
       end
 
diff --git a/test/Makefile b/test/Makefile
index db71a4f..de2d64e 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -3,8 +3,8 @@ include ../Makefile.cfg
 NASM ?= nasm
 VOODOOC ?= env RUBYLIB=$(PWD)/../lib:$(RUBYLIB) ../bin/voodooc
 
-TARGETS = bitwise call div fact goto hello if many-vars mod mul plusminus \
-	set-byte set-word tail-calls vtable 99bottles gcd
+TARGETS = at bitwise call div fact goto hello if many-vars mod mul \
+	plusminus set-byte set-word tail-calls vtable 99bottles gcd
 
 all : $(TARGETS)
 
diff --git a/test/test b/test/test
index a95f87d..aa626e7 100755
--- a/test/test
+++ b/test/test
@@ -36,6 +36,8 @@ run_test2 hello "Hello, world!"
 
 run_test1 call
 
+run_test1 at
+
 run_test1 if
 
 run_test1 goto
-- 
2.11.4.GIT