diff --git a/ChangeLog b/ChangeLog
index 67f302b..f8541bb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,38 @@
+Sun May 10 22:42:07 2009  Minero Aoki  <aamine@loveruby.net>
+
+	* net/loveruby/cflat/sysdep/x86: new package.
+
+	* net/loveruby/cflat/asm/ELFConstants.java ->
+	  net/loveruby/cflat/sysdep/x86
+
+	* net/loveruby/cflat/asm/AssemblyFile.java ->
+	  net/loveruby/cflat/sysdep/x86
+
+	net/loveruby/cflat/asm/Register.java
+
+	* net/loveruby/cflat/platform/X86Linux.java ->
+	  net/loveruby/cflat/sysdep/x86
+
+	* net/loveruby/cflat/compiler/CodeGenerator.java ->
+	  net/loveruby/cflat/sysdep/x86
+
+	* net/loveruby/cflat/platform/Platform.java ->
+	  net/loveruby/cflat/compiler
+
+	* net/loveruby/cflat/sysdep/x86/Register.java: new file.
+
+	* net/loveruby/cflat/compiler/Options.java: new method
+	  #codeGenerator.
+
+	* net/loveruby/cflat/compiler/Compiler.java: get CodeGenerator
+	  from Options.
+
+	* net/loveruby/cflat/compiler/CodeGeneratorOptions.java: make
+	  public.
+
+	* net/loveruby/cflat/ir/IR.java: now naturalType is useless
+	  (provided by CodeGenerator).
+
 Sun May 10 20:24:13 2009  Minero Aoki  <aamine@loveruby.net>
 
 	* net/loveruby/cflat/asm/Assembler.java -> AssemblyFile.java
diff --git a/net/loveruby/cflat/asm/Register.java b/net/loveruby/cflat/asm/Register.java
index fbf8702..239d31c 100644
--- a/net/loveruby/cflat/asm/Register.java
+++ b/net/loveruby/cflat/asm/Register.java
@@ -1,31 +1,15 @@
 package net.loveruby.cflat.asm;
 
-public class Register extends AsmOperand {
+abstract public class Register extends AsmOperand {
     protected int size;
     protected String name;
 
-    // platform dependent
-    static final protected int naturalSize = 4;
-
-    public Register(String name) {
-        this(naturalSize, name);
-    }
-
     public Register(int size, String name) {
         this.size = size;
         this.name = name;
     }
 
-    public Register forType(Type t) {
-        switch (t.size()) {
-        case 1:
-        case 2:
-        case 4:
-            return new Register(t.size(), name);
-        default:
-            throw new Error("invalid register size: " + t.size());
-        }
-    }
+    abstract public Register forType(Type t);
 
     public boolean isRegister() {
         return true;
@@ -40,9 +24,7 @@ public class Register extends AsmOperand {
         return name.hashCode();
     }
 
-    /**
-     * size difference does NOT matter.
-     */
+    /** size difference does NOT matter. */
     public boolean equals(Register reg) {
         return name.equals(reg.baseName());
     }
@@ -51,36 +33,14 @@ public class Register extends AsmOperand {
         return name;
     }
 
+    // default implementation
     public String name() {
-        switch (size) {
-        case 1: return lowerByteRegister(name);
-        case 2: return name;
-        case 4: return "e" + name;
-        default:
-            throw new Error("invalid register size: " + size);
-        }
-    }
-
-    protected String lowerByteRegister(String baseName) {
-        if (! hasLowerByteRegister(baseName)) {
-            throw new Error("does not have lower-byte register: " + baseName);
-        }
-        return baseName.substring(0, 1) + "l";
-    }
-
-    protected boolean hasLowerByteRegister(String baseName) {
-        if (baseName.equals("ax")) return true;
-        if (baseName.equals("bx")) return true;
-        if (baseName.equals("cx")) return true;
-        if (baseName.equals("dx")) return true;
-        return false;
+        return name;
     }
 
     public void collectStatistics(AsmStatistics stats) {
         stats.registerUsed(this);
     }
 
-    public String toSource(SymbolTable table) {
-        return "%" + name();
-    }
+    abstract public String toSource(SymbolTable table);
 }
diff --git a/net/loveruby/cflat/compiler/CodeGeneratorOptions.java b/net/loveruby/cflat/compiler/CodeGeneratorOptions.java
index d115a8d..713c6e2 100644
--- a/net/loveruby/cflat/compiler/CodeGeneratorOptions.java
+++ b/net/loveruby/cflat/compiler/CodeGeneratorOptions.java
@@ -2,7 +2,7 @@ package net.loveruby.cflat.compiler;
 import net.loveruby.cflat.asm.*;
 import java.util.*;
 
-class CodeGeneratorOptions {
+public class CodeGeneratorOptions {
     protected int optimizeLevel;
     protected boolean generatePIC;
     protected boolean generatePIE;
diff --git a/net/loveruby/cflat/compiler/Compiler.java b/net/loveruby/cflat/compiler/Compiler.java
index 0d54a41..6a23cf5 100644
--- a/net/loveruby/cflat/compiler/Compiler.java
+++ b/net/loveruby/cflat/compiler/Compiler.java
@@ -212,8 +212,7 @@ public class Compiler {
     }
 
     protected String generateAssembly(IR ir, Options opts) {
-        CodeGenerator gen = new CodeGenerator(
-                opts.genOptions(), opts.platform(), errorHandler);
+        CodeGenerator gen = opts.codeGenerator(errorHandler);
         return gen.generate(ir);
     }
 
diff --git a/net/loveruby/cflat/compiler/Options.java b/net/loveruby/cflat/compiler/Options.java
index 6eddea9..27d72fc 100644
--- a/net/loveruby/cflat/compiler/Options.java
+++ b/net/loveruby/cflat/compiler/Options.java
@@ -1,5 +1,5 @@
 package net.loveruby.cflat.compiler;
-import net.loveruby.cflat.platform.*;
+import net.loveruby.cflat.sysdep.x86.X86Linux;
 import net.loveruby.cflat.type.TypeTable;
 import net.loveruby.cflat.asm.*;
 import net.loveruby.cflat.exception.*;
@@ -77,6 +77,10 @@ class Options {
         return platform.typeTable();
     }
 
+    CodeGenerator codeGenerator(ErrorHandler errorHandler) {
+        return platform.codeGenerator(genOptions, errorHandler);
+    }
+
     LibraryLoader loader() {
         return this.loader;
     }
@@ -93,10 +97,6 @@ class Options {
         return this.debugParser;
     }
 
-    CodeGeneratorOptions genOptions() {
-        return genOptions;
-    }
-
     List<String> asOptions() {
         return this.asOptions;
     }
diff --git a/net/loveruby/cflat/compiler/Platform.java b/net/loveruby/cflat/compiler/Platform.java
new file mode 100644
index 0000000..236d17e
--- /dev/null
+++ b/net/loveruby/cflat/compiler/Platform.java
@@ -0,0 +1,7 @@
+package net.loveruby.cflat.compiler;
+import net.loveruby.cflat.type.TypeTable;
+
+public interface Platform {
+    TypeTable typeTable();
+    CodeGenerator codeGenerator(CodeGeneratorOptions opts, ErrorHandler h);
+}
diff --git a/net/loveruby/cflat/ir/IR.java b/net/loveruby/cflat/ir/IR.java
index fde932d..b83e4a4 100644
--- a/net/loveruby/cflat/ir/IR.java
+++ b/net/loveruby/cflat/ir/IR.java
@@ -78,11 +78,6 @@ public class IR {
         return constantTable;
     }
 
-    public net.loveruby.cflat.asm.Type naturalType() {
-        // platform dependent!!!
-        return Type.INT32;
-    }
-
     public void dump() {
         dump(System.out);
     }
diff --git a/net/loveruby/cflat/platform/Platform.java b/net/loveruby/cflat/platform/Platform.java
deleted file mode 100644
index dbb4654..0000000
--- a/net/loveruby/cflat/platform/Platform.java
+++ /dev/null
@@ -1,10 +0,0 @@
-package net.loveruby.cflat.platform;
-
-public interface Platform {
-    net.loveruby.cflat.type.TypeTable typeTable();
-    net.loveruby.cflat.asm.Type naturalType();
-    long align(long size);
-    long stackWordSize();
-    long alignStack(long size);
-    long stackSizeFromWordNum(long numWords);
-}
diff --git a/net/loveruby/cflat/platform/X86Linux.java b/net/loveruby/cflat/platform/X86Linux.java
deleted file mode 100644
index ed6f92d..0000000
--- a/net/loveruby/cflat/platform/X86Linux.java
+++ /dev/null
@@ -1,36 +0,0 @@
-package net.loveruby.cflat.platform;
-import net.loveruby.cflat.type.TypeTable;
-import net.loveruby.cflat.asm.Type;
-import net.loveruby.cflat.utils.AsmUtils;
-
-public class X86Linux implements Platform {
-    static final Type naturalType = Type.INT32;
-    static final long alignment = 4;
-    // #@@range/stackParams{
-    static final long stackWordSize = 4;
-    // #@@}
-
-    public TypeTable typeTable() {
-        return TypeTable.ilp32();
-    }
-
-    public Type naturalType() {
-        return naturalType;
-    }
-
-    public long align(long size) {
-        return AsmUtils.align(size, alignment);
-    }
-
-    public long stackWordSize() {
-        return stackWordSize;
-    }
-
-    public long alignStack(long size) {
-        return AsmUtils.align(size, stackWordSize);
-    }
-
-    public long stackSizeFromWordNum(long num) {
-        return num * stackWordSize;
-    }
-}
diff --git a/net/loveruby/cflat/asm/AssemblyFile.java b/net/loveruby/cflat/sysdep/x86/AssemblyFile.java
similarity index 97%
rename from net/loveruby/cflat/asm/AssemblyFile.java
rename to net/loveruby/cflat/sysdep/x86/AssemblyFile.java
index 0f55b85..19de08e 100644
--- a/net/loveruby/cflat/asm/AssemblyFile.java
+++ b/net/loveruby/cflat/sysdep/x86/AssemblyFile.java
@@ -1,4 +1,5 @@
-package net.loveruby.cflat.asm;
+package net.loveruby.cflat.sysdep.x86;
+import net.loveruby.cflat.asm.*;
 import net.loveruby.cflat.utils.*;
 import java.util.*;
 
@@ -21,11 +22,7 @@ public class AssemblyFile {
         this.assemblies.addAll(assemblies);
     }
 
-    static final public String CODE_SYMBOL_BASE = ".L";
-    static final public String CONST_SYMBOL_BASE = ".LC";
-
-    public String toSource() {
-        SymbolTable symbolTable = new SymbolTable(CODE_SYMBOL_BASE);
+    public String toSource(SymbolTable symbolTable) {
         StringBuffer buf = new StringBuffer();
         for (Assembly asm : assemblies) {
             buf.append(asm.toSource(symbolTable));
diff --git a/net/loveruby/cflat/compiler/CodeGenerator.java b/net/loveruby/cflat/sysdep/x86/CodeGenerator.java
similarity index 96%
rename from net/loveruby/cflat/compiler/CodeGenerator.java
rename to net/loveruby/cflat/sysdep/x86/CodeGenerator.java
index 13d79cc..c9d9b53 100644
--- a/net/loveruby/cflat/compiler/CodeGenerator.java
+++ b/net/loveruby/cflat/sysdep/x86/CodeGenerator.java
@@ -1,15 +1,19 @@
-package net.loveruby.cflat.compiler;
-import net.loveruby.cflat.platform.Platform;
+package net.loveruby.cflat.sysdep.x86;
+import net.loveruby.cflat.compiler.CodeGeneratorOptions;
+import net.loveruby.cflat.compiler.ErrorHandler;
 import net.loveruby.cflat.ast.Location;
 import net.loveruby.cflat.entity.*;
 import net.loveruby.cflat.ir.*;
 import net.loveruby.cflat.asm.*;
+import net.loveruby.cflat.utils.AsmUtils;
 import java.util.*;
 
-public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
+public class CodeGenerator
+        implements net.loveruby.cflat.compiler.CodeGenerator,
+                IRVisitor<Void,Void>,
+                ELFConstants {
     // #@@range/ctor{
     protected CodeGeneratorOptions options;
-    protected Platform platform;
     protected ErrorHandler errorHandler;
     protected LinkedList<AssemblyFile> asStack;
     protected AssemblyFile as;
@@ -17,10 +21,8 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
     protected Label epilogue;
 
     public CodeGenerator(CodeGeneratorOptions options,
-                         Platform platform,
                          ErrorHandler errorHandler) {
         this.options = options;
-        this.platform = platform;
         this.errorHandler = errorHandler;
         this.asStack = new LinkedList<AssemblyFile>();
     }
@@ -28,10 +30,12 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
 
     /** Compiles IR and generates assembly code. */
     // #@@range/generate{
+    static final private String CONST_SYMBOL_BASE = ".LC";
+    static final private String LABEL_SYMBOL_BASE = ".L";
+
     public String generate(IR ir) {
-        this.naturalType = ir.naturalType();
         pushAssembler();
-        SymbolTable constSymbols = new SymbolTable(AssemblyFile.CONST_SYMBOL_BASE);
+        SymbolTable constSymbols = new SymbolTable(CONST_SYMBOL_BASE);
         for (ConstantEntry ent : ir.constantTable().entries()) {
             locateConstant(ent, constSymbols);
         }
@@ -42,11 +46,13 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
             locateFunction(func);
         }
         compileIR(ir);
-        return popAssembler().toSource();
+        return popAssembler().toSource(new SymbolTable(LABEL_SYMBOL_BASE));
     }
     // #@@}
 
     // #@@range/pushAssembler{
+    static final private Type NATURAL_TYPE = Type.INT32;
+
     protected void pushAssembler() {
         this.as = new AssemblyFile(naturalType);
         asStack.add(this.as);
@@ -226,14 +232,12 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
     // #@@}
 
     // #@@range/globalSymbol{
-    // platform dependent
     protected Symbol globalSymbol(String sym) {
         return new NamedSymbol(sym);
     }
     // #@@}
 
     // #@@range/privateSymbol{
-    // platform dependent
     protected Symbol privateSymbol(String sym) {
         return new NamedSymbol(sym);
     }
@@ -351,6 +355,18 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
      * ======================= stack bottom
      */
 
+    // #@@range/stackParams{
+    static final private long STACK_WORD_SIZE = 4;
+    // #@@}
+
+    public long alignStack(long size) {
+        return AsmUtils.align(size, STACK_WORD_SIZE);
+    }
+
+    public long stackSizeFromWordNum(long numWords) {
+        return numWords * STACK_WORD_SIZE;
+    }
+
     /** Compiles a function. */
     // #@@range/compileFunction{
     public void compileFunction(DefinedFunction func) {
@@ -376,7 +392,7 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
         AsmStatistics stats = AsmStatistics.collect(bodyAsms);
         bodyAsms = reduceLabels(bodyAsms, stats);
         List<Register> saveRegs = usedCalleeSavedRegistersWithoutBP(stats);
-        long saveRegsBytes = platform.stackSizeFromWordNum(saveRegs.size());
+        long saveRegsBytes = stackSizeFromWordNum(saveRegs.size());
         long lvarBytes = allocateLocalVariables(
                 func.body().scope(), saveRegsBytes);
         fixTmpOffsets(bodyAsms, saveRegsBytes + lvarBytes);
@@ -477,7 +493,6 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
 
     protected List<Register> calleeSavedRegistersCache = null;
 
-    // platform dependent
     protected List<Register> calleeSavedRegisters() {
         if (calleeSavedRegistersCache == null) {
             List<Register> regs = new ArrayList<Register>();
@@ -536,7 +551,7 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
     protected void allocateParameters(DefinedFunction func) {
         long numWords = paramStartWordNum;
         for (Parameter var : func.parameters()) {
-            var.setMemref(mem(platform.stackSizeFromWordNum(numWords), bp()));
+            var.setMemref(mem(stackSizeFromWordNum(numWords), bp()));
             numWords++;
         }
     }
@@ -570,7 +585,7 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
     protected long allocateScope(LocalScope scope, long parentStackLen) {
         long len = parentStackLen;
         for (DefinedVariable var : scope.localVariables()) {
-            len = platform.alignStack(len + var.allocSize());
+            len = alignStack(len + var.allocSize());
             fixMemref((IndirectMemoryReference)var.memref(), -len);
         }
         // Allocate local variables in child scopes.
@@ -630,7 +645,7 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
 
     // #@@range/virtualPush{
     protected void virtualPush(Register reg) {
-        extendVirtualStack(platform.stackWordSize());
+        extendVirtualStack(STACK_WORD_SIZE);
         as.relocatableMov(reg, stackTop());
         if (options.isVerboseAsm()) {
             as.comment("push " + reg.name() + " -> " + stackTop());
@@ -644,7 +659,7 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
             as.comment("pop  " + reg.name() + " <- " + stackTop());
         }
         as.relocatableMov(stackTop(), reg);
-        rewindVirtualStack(platform.stackWordSize());
+        rewindVirtualStack(STACK_WORD_SIZE);
     }
     // #@@}
 
@@ -694,7 +709,7 @@ public class CodeGenerator implements IRVisitor<Void,Void>, ELFConstants {
         }
         // rewind stack
         // >4 bytes arguments are not supported.
-        rewindStack(platform.stackSizeFromWordNum(node.numArgs()));
+        rewindStack(stackSizeFromWordNum(node.numArgs()));
         return null;
     }
     // #@@}
diff --git a/net/loveruby/cflat/asm/ELFConstants.java b/net/loveruby/cflat/sysdep/x86/ELFConstants.java
similarity index 95%
rename from net/loveruby/cflat/asm/ELFConstants.java
rename to net/loveruby/cflat/sysdep/x86/ELFConstants.java
index ba00895..18c6fd6 100644
--- a/net/loveruby/cflat/asm/ELFConstants.java
+++ b/net/loveruby/cflat/sysdep/x86/ELFConstants.java
@@ -1,4 +1,4 @@
-package net.loveruby.cflat.asm;
+package net.loveruby.cflat.sysdep.x86;
 
 public interface ELFConstants {
     // Flags
diff --git a/net/loveruby/cflat/sysdep/x86/Register.java b/net/loveruby/cflat/sysdep/x86/Register.java
new file mode 100644
index 0000000..7af7d12
--- /dev/null
+++ b/net/loveruby/cflat/sysdep/x86/Register.java
@@ -0,0 +1,54 @@
+package net.loveruby.cflat.sysdep.x86;
+import net.loveruby.cflat.asm.*;
+
+public class Register extends net.loveruby.cflat.asm.Register {
+    static final private int naturalSize = 4;
+
+    public Register(String name) {
+        super(naturalSize, name);
+    }
+
+    public Register(int size, String name) {
+        super(size, name);
+    }
+
+    public Register forType(Type t) {
+        switch (t.size()) {
+        case 1:
+        case 2:
+        case 4:
+            return new Register(t.size(), name);
+        default:
+            throw new Error("invalid register size: " + t.size());
+        }
+    }
+
+    public String name() {
+        switch (size) {
+        case 1: return lowerByteRegister(name);
+        case 2: return name;
+        case 4: return "e" + name;
+        default:
+            throw new Error("invalid register size: " + size);
+        }
+    }
+
+    private String lowerByteRegister(String baseName) {
+        if (! hasLowerByteRegister(baseName)) {
+            throw new Error("does not have lower-byte register: " + baseName);
+        }
+        return baseName.substring(0, 1) + "l";
+    }
+
+    private boolean hasLowerByteRegister(String baseName) {
+        if (baseName.equals("ax")) return true;
+        if (baseName.equals("bx")) return true;
+        if (baseName.equals("cx")) return true;
+        if (baseName.equals("dx")) return true;
+        return false;
+    }
+
+    public String toSource(SymbolTable table) {
+        return "%" + name();
+    }
+}
diff --git a/net/loveruby/cflat/sysdep/x86/X86Linux.java b/net/loveruby/cflat/sysdep/x86/X86Linux.java
new file mode 100644
index 0000000..500cbf2
--- /dev/null
+++ b/net/loveruby/cflat/sysdep/x86/X86Linux.java
@@ -0,0 +1,16 @@
+package net.loveruby.cflat.sysdep.x86;
+import net.loveruby.cflat.compiler.Platform;
+import net.loveruby.cflat.compiler.CodeGeneratorOptions;
+import net.loveruby.cflat.compiler.ErrorHandler;
+import net.loveruby.cflat.type.TypeTable;
+
+public class X86Linux implements Platform {
+    public TypeTable typeTable() {
+        return TypeTable.ilp32();
+    }
+
+    public CodeGenerator codeGenerator(
+            CodeGeneratorOptions opts, ErrorHandler h) {
+        return new CodeGenerator(opts, h);
+    }
+}