[Tarantool-patches] [PATCH] luajit: adde flag of partial comp. with Lua 5.2

[Olga Arkhangelskaia <arkholga@tarantool.org>]

Although we do not turn on full compatibility with Lua 5.2 we do need some of
its features (eg. __pairs/__ipairs).This functionality brakes existing code.
However, if the necessity is very high or is strongly demanded we should
have possibility to use it. We introduce LUAJIT_ENABLE_LUA52COMPAT_PART
flag.

Some of the Lua 5.2's features that are likely to break existing code can be
turned on under this flag. At the moment it is pirs/ipairs metmethod.
---
 src/Makefile    | 4 ++++
 src/lib_base.c  | 4 ++--
 src/lj_arch.h   | 6 ++++++
 src/lj_obj.h    | 2 +-
 src/vm_x86.dasc | 4 ++--
 5 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/Makefile b/src/Makefile
index 827d4a4..e8fd91a 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -101,6 +101,10 @@ XCFLAGS=
 # Note: this does not provide full compatibility with Lua 5.2 at this time.
 #XCFLAGS+= -DLUAJIT_ENABLE_LUA52COMPAT
 #
+#Features from Lua 5.2 that was demanded more than once or are essential for
+#for the project. At the moment only pairs/ipairs can be enabled via this flag.
+#XCFLAGS+= -DLUAJIT_ENABLE_LUA52COMPAT_PART
+#
 # Disable the JIT compiler, i.e. turn LuaJIT into a pure interpreter.
 #XCFLAGS+= -DLUAJIT_DISABLE_JIT
 #
diff --git a/src/lib_base.c b/src/lib_base.c
index 3a75787..6cc0fcc 100644
--- a/src/lib_base.c
+++ b/src/lib_base.c
@@ -81,12 +81,12 @@ LJLIB_ASM(next)
   return FFH_UNREACHABLE;
 }
 
-#if LJ_52 || LJ_HASFFI
+#if LJ_52_PART || LJ_HASFFI
 static int ffh_pairs(lua_State *L, MMS mm)
 {
   TValue *o = lj_lib_checkany(L, 1);
   cTValue *mo = lj_meta_lookup(L, o, mm);
-  if ((LJ_52 || tviscdata(o)) && !tvisnil(mo)) {
+  if ((LJ_52_PART || tviscdata(o)) && !tvisnil(mo)) {
     L->top = o+1;  /* Only keep one argument. */
     copyTV(L, L->base-1-LJ_FR2, mo);  /* Replace callable. */
     return FFH_TAILCALL;
diff --git a/src/lj_arch.h b/src/lj_arch.h
index c8d7138..39d70d5 100644
--- a/src/lj_arch.h
+++ b/src/lj_arch.h
@@ -564,4 +564,10 @@
 #define LJ_52			0
 #endif
 
+/* Partial compatibility with Lua 5.2 */
+#if defined(LUAJIT_ENABLE_LUA52COMPAT_PART) || defined (LUAJIT_ENABLE_LUA52COMPAT)
+#define LJ_52_PART			1
+#else
+#define LJ_52_PART			0
+#endif
 #endif
diff --git a/src/lj_obj.h b/src/lj_obj.h
index f368578..3788cee 100644
--- a/src/lj_obj.h
+++ b/src/lj_obj.h
@@ -530,7 +530,7 @@ enum {
 #define MMDEF_FFI(_)
 #endif
 
-#if LJ_52 || LJ_HASFFI
+#if LJ_52 || LJ_HASFFI || LJ_52_PART
 #define MMDEF_PAIRS(_) _(pairs) _(ipairs)
 #else
 #define MMDEF_PAIRS(_)
diff --git a/src/vm_x86.dasc b/src/vm_x86.dasc
index 56bee14..ad6216e 100644
--- a/src/vm_x86.dasc
+++ b/src/vm_x86.dasc
@@ -1724,7 +1724,7 @@ static void build_subroutines(BuildCtx *ctx)
   |.ffunc_1 pairs
   |  mov TAB:RB, [BASE]
   |  cmp dword [BASE+4], LJ_TTAB;  jne ->fff_fallback
-#if LJ_52
+#if LJ_52_PART
   |  cmp dword TAB:RB->metatable, 0; jne ->fff_fallback
 #endif
   |  mov CFUNC:RB, [BASE-8]
@@ -1791,7 +1791,7 @@ static void build_subroutines(BuildCtx *ctx)
   |.ffunc_1 ipairs
   |  mov TAB:RB, [BASE]
   |  cmp dword [BASE+4], LJ_TTAB;  jne ->fff_fallback
-#if LJ_52
+#if LJ_52_PART
   |  cmp dword TAB:RB->metatable, 0; jne ->fff_fallback
 #endif
   |  mov CFUNC:RB, [BASE-8]
-- 
2.20.1 (Apple Git-117)