From d9cb5d4eee50901d16d5ed9561605fa945badb8d Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Tue, 5 Nov 2013 20:33:24 +0900
Subject: [PATCH] nan-boxing support

---
 include/picconf.h      |  3 ++
 include/picrin/value.h | 33 ++++++++++++++++++++
 src/value.c            | 70 +++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 105 insertions(+), 1 deletion(-)

diff --git a/include/picconf.h b/include/picconf.h
index 62b42bc1..3808701a 100644
--- a/include/picconf.h
+++ b/include/picconf.h
@@ -4,6 +4,9 @@
 /* switch normal VM and direct threaded VM */
 #define PIC_DIRECT_THREADED_VM 1
 
+/* switch internal value representation */
+#define PIC_NAN_BOXING 1
+
 /* enable readline module */
 #define PIC_ENABLE_READLINE 1
 
diff --git a/include/picrin/value.h b/include/picrin/value.h
index ce2d0af2..1ca74b30 100644
--- a/include/picrin/value.h
+++ b/include/picrin/value.h
@@ -16,6 +16,37 @@ enum pic_vtype {
   PIC_VTYPE_HEAP
 };
 
+#if PIC_NAN_BOXING
+
+/**
+ * value representation by nan-boxing:
+ *   float : FFFFFFFFFFFFFFFF FFFFFFFFFFFFFFFF FFFFFFFFFFFFFFFF FFFFFFFFFFFFFFFF
+ *   ptr   : 111111111111TTTT PPPPPPPPPPPPPPPP PPPPPPPPPPPPPPPP PPPPPPPPPPPPPPPP
+ *   int   : 1111111111110110 0000000000000000 IIIIIIIIIIIIIIII IIIIIIIIIIIIIIII
+ *   sym   : 1111111111110111 0000000000000000 SSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSS
+ *   char  : 1111111111111000 0000000000000000 CCCCCCCCCCCCCCCC ................
+ */
+typedef struct {
+  union {
+    void *data;
+    double f;
+    struct {
+      union {
+	int i;
+	pic_sym sym;
+	char c;
+      };
+      unsigned int type_;
+    };
+  } u;
+} pic_value;
+
+#define pic_ptr(v) ((void *)((long long)0xffffffffffff & (long long)(v).u.data))
+#define pic_vtype(v) (((v).u.type_ & 0xf0000)>>16)
+#define pic_init_value(v,vtype) (((v).u.type_ = ((unsigned int)0xfff00000|((vtype)<<16))), (v).u.i = 0)
+
+#else
+
 typedef struct {
   enum pic_vtype type;
   union {
@@ -31,6 +62,8 @@ typedef struct {
 #define pic_vtype(v) ((v).type)
 #define pic_init_value(v,vtype) ((v).type = (vtype), (v).u.data = NULL)
 
+#endif
+
 enum pic_tt {
   /* immediate */
   PIC_TT_NIL,
diff --git a/src/value.c b/src/value.c
index 750dd08d..2ea602bc 100644
--- a/src/value.c
+++ b/src/value.c
@@ -1,7 +1,43 @@
 #include <stdlib.h>
 #include <stdbool.h>
 
-#include "picrin/value.h"
+#include "picrin.h"
+
+#if PIC_NAN_BOXING
+
+enum pic_tt
+pic_type(pic_value v)
+{
+  if ((int)0xfff00000 >= v.u.type_)
+    return PIC_TT_FLOAT;
+
+  switch (pic_vtype(v)) {
+  case PIC_VTYPE_NIL:
+    return PIC_TT_NIL;
+  case PIC_VTYPE_TRUE:
+    return PIC_TT_BOOL;
+  case PIC_VTYPE_FALSE:
+    return PIC_TT_BOOL;
+  case PIC_VTYPE_UNDEF:
+    return PIC_TT_UNDEF;
+  case PIC_VTYPE_FLOAT:
+    return PIC_TT_FLOAT;
+  case PIC_VTYPE_INT:
+    return PIC_TT_INT;
+  case PIC_VTYPE_SYMBOL:
+    return PIC_TT_SYMBOL;
+  case PIC_VTYPE_CHAR:
+    return PIC_TT_CHAR;
+  case PIC_VTYPE_EOF:
+    return PIC_TT_EOF;
+  case PIC_VTYPE_HEAP:
+    return ((struct pic_object *)pic_ptr(v))->tt;
+  }
+  /* logic flaw (suppress warnings gcc will emit) */
+  abort();
+}
+
+#else
 
 enum pic_tt
 pic_type(pic_value v)
@@ -32,6 +68,8 @@ pic_type(pic_value v)
   abort();
 }
 
+#endif
+
 const char *
 pic_type_repr(enum pic_tt tt)
 {
@@ -91,6 +129,34 @@ pic_bool_value(bool b)
   return v;
 }
 
+#if PIC_NAN_BOXING
+
+pic_value
+pic_obj_value(void *ptr)
+{
+  pic_value v;
+
+  pic_init_value(v, PIC_VTYPE_HEAP);
+  v.u.data = (void*)((long long)v.u.data | ((long long)ptr));
+  return v;
+}
+
+pic_value
+pic_float_value(double f)
+{
+  pic_value v;
+
+  if (f != f) {
+    v.u.type_ = 0x7ff80000;
+    v.u.i = 0;
+  } else {
+    v.u.f = f;
+  }
+  return v;
+}
+
+#else
+
 pic_value
 pic_obj_value(void *ptr)
 {
@@ -111,6 +177,8 @@ pic_float_value(double f)
   return v;
 }
 
+#endif
+
 pic_value
 pic_int_value(int i)
 {