[Tarantool-patches] [PATCH v5] build: introduce LUAJIT_ENABLE_PAIRSMM flag

[Tarantool-patches] [PATCH v5] build: introduce LUAJIT_ENABLE_PAIRSMM flag

[Olga Arkhangelskaia]

Adds LUAJIT_ENABLE_PAIRSMM flag as a build option for luajit.
If the flag is set, pairs/ipairs metamethods are available in Lua 5.1.
For tarantool this option is enabled by default.

Part of #4560
Branch:https://github.com/tarantool/luajit/tree/OKriw/gh-4560-Enable-LUAJIT_ENABLE_LUA52COMPAT-when-bulding-luajit

v1: https://lists.tarantool.org/pipermail/tarantool-patches/2019-November/012466.html
v2: https://lists.tarantool.org/pipermail/tarantool-patches/2019-November/012489.html
v3: https://lists.tarantool.org/pipermail/tarantool-patches/2019-November/012527.html

Changes in v2:
- flag is renamed
- now flag is used only for pairsmm
- added test case
Changes in v3:
- added flag to other vm*
- changed comments and commit msg
Changes in v4:
- fixed errors in arm/arm64 vm
- rewrited commit msg, subject, comment 

Changes in v5:
- fixed test name
---
 src/Makefile          |  3 +++
 src/lib_base.c        |  4 ++--
 src/lj_arch.h         |  6 ++++++
 src/lj_obj.h          |  2 +-
 src/vm_arm.dasc       |  8 +++----
 src/vm_arm64.dasc     |  8 +++----
 src/vm_mips.dasc      |  4 ++--
 src/vm_mips64.dasc    |  4 ++--
 src/vm_ppc.dasc       |  4 ++--
 src/vm_x64.dasc       |  4 ++--
 src/vm_x86.dasc       |  4 ++--
 test/mmpairs.test.lua | 50 +++++++++++++++++++++++++++++++++++++++++++
 12 files changed, 80 insertions(+), 21 deletions(-)
 create mode 100755 test/mmpairs.test.lua

diff --git a/src/Makefile b/src/Makefile
index aca656d..a1a39d2 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -101,6 +101,9 @@ XCFLAGS=
 # Note: this does not provide full compatibility with Lua 5.2 at this time.
 #XCFLAGS+= -DLUAJIT_ENABLE_LUA52COMPAT
 #
+#Enable pairs/ipairs methametods from  Lua 5.2.
+#XCFLAGS+= -DLUAJIT_ENABLE_PAIRSMM
+#
 # 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..950a580 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_PAIRSMM || 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_PAIRSMM || 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..0c5230c 100644
--- a/src/lj_arch.h
+++ b/src/lj_arch.h
@@ -564,4 +564,10 @@
 #define LJ_52			0
 #endif
 
+/* Enabling pairs/ipairs metamethods for Lua 5.1 */
+#if defined(LUAJIT_ENABLE_PAIRSMM) || defined (LUAJIT_ENABLE_LUA52COMPAT)
+#define LJ_PAIRSMM			1
+#else
+#define LJ_PAIRSMM			0
+#endif
 #endif
diff --git a/src/lj_obj.h b/src/lj_obj.h
index f368578..49467fb 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_PAIRSMM || LJ_HASFFI
 #define MMDEF_PAIRS(_) _(pairs) _(ipairs)
 #else
 #define MMDEF_PAIRS(_)
diff --git a/src/vm_arm.dasc b/src/vm_arm.dasc
index d4cdaf5..a98ea12 100644
--- a/src/vm_arm.dasc
+++ b/src/vm_arm.dasc
@@ -1133,12 +1133,12 @@ static void build_subroutines(BuildCtx *ctx)
   |
   |.ffunc_1 pairs
   |  checktab CARG2, ->fff_fallback
-#if LJ_52
+#if LJ_PAIRSMM
   |  ldr TAB:RB, TAB:CARG1->metatable
 #endif
   |   ldrd CFUNC:CARG34, CFUNC:CARG3->upvalue[0]
   |    ldr PC, [BASE, FRAME_PC]
-#if LJ_52
+#if LJ_PAIRSMM
   |  cmp TAB:RB, #0
   |  bne ->fff_fallback
 #endif
@@ -1183,12 +1183,12 @@ static void build_subroutines(BuildCtx *ctx)
   |
   |.ffunc_1 ipairs
   |  checktab CARG2, ->fff_fallback
-#if LJ_52
+#if LJ_PAIRSMM
   |  ldr TAB:RB, TAB:CARG1->metatable
 #endif
   |   ldrd CFUNC:CARG34, CFUNC:CARG3->upvalue[0]
   |    ldr PC, [BASE, FRAME_PC]
-#if LJ_52
+#if LJ_PAIRSMM
   |  cmp TAB:RB, #0
   |  bne ->fff_fallback
 #endif
diff --git a/src/vm_arm64.dasc b/src/vm_arm64.dasc
index 3eaf376..fcd9aad 100644
--- a/src/vm_arm64.dasc
+++ b/src/vm_arm64.dasc
@@ -1103,12 +1103,12 @@ static void build_subroutines(BuildCtx *ctx)
   |
   |.ffunc_1 pairs
   |  checktp TMP1, CARG1, LJ_TTAB, ->fff_fallback
-#if LJ_52
+#if LJ_PAIRSMM
   |  ldr TAB:CARG2, TAB:TMP1->metatable
 #endif
   |   ldr CFUNC:CARG4, CFUNC:CARG3->upvalue[0]
   |    ldr PC, [BASE, FRAME_PC]
-#if LJ_52
+#if LJ_PAIRSMM
   |  cbnz TAB:CARG2, ->fff_fallback
 #endif
   |  mov RC, #(3+1)*8
@@ -1146,12 +1146,12 @@ static void build_subroutines(BuildCtx *ctx)
   |
   |.ffunc_1 ipairs
   |  checktp TMP1, CARG1, LJ_TTAB, ->fff_fallback
-#if LJ_52
+#if LJ_PAIRSMM
   |  ldr TAB:CARG2, TAB:TMP1->metatable
 #endif
   |   ldr CFUNC:CARG4, CFUNC:CARG3->upvalue[0]
   |    ldr PC, [BASE, FRAME_PC]
-#if LJ_52
+#if LJ_PAIRSMM
   |  cbnz TAB:CARG2, ->fff_fallback
 #endif
   |  mov RC, #(3+1)*8
diff --git a/src/vm_mips.dasc b/src/vm_mips.dasc
index 1afd611..81de610 100644
--- a/src/vm_mips.dasc
+++ b/src/vm_mips.dasc
@@ -1292,7 +1292,7 @@ static void build_subroutines(BuildCtx *ctx)
   |  li AT, LJ_TTAB
   |  bne SFARG1HI, AT, ->fff_fallback
   |.  lw PC, FRAME_PC(BASE)
-#if LJ_52
+#if LJ_PAIRSMM
   |  lw TAB:TMP2, TAB:SFARG1LO->metatable
   |  lw TMP0, CFUNC:RB->upvalue[0].u32.hi
   |   lw TMP1, CFUNC:RB->upvalue[0].u32.lo
@@ -1358,7 +1358,7 @@ static void build_subroutines(BuildCtx *ctx)
   |  li AT, LJ_TTAB
   |  bne SFARG1HI, AT, ->fff_fallback
   |.  lw PC, FRAME_PC(BASE)
-#if LJ_52
+#if LJ_PAIRSMM
   |  lw TAB:TMP2, TAB:SFARG1LO->metatable
   |  lw TMP0, CFUNC:RB->upvalue[0].u32.hi
   |   lw TMP1, CFUNC:RB->upvalue[0].u32.lo
diff --git a/src/vm_mips64.dasc b/src/vm_mips64.dasc
index c06270a..4cdff5e 100644
--- a/src/vm_mips64.dasc
+++ b/src/vm_mips64.dasc
@@ -1306,7 +1306,7 @@ static void build_subroutines(BuildCtx *ctx)
   |.ffunc_1 pairs
   |  checktp TAB:TMP1, CARG1, -LJ_TTAB, ->fff_fallback
   |  ld PC, FRAME_PC(BASE)
-#if LJ_52
+#if LJ_PAIRSMM
   |  ld TAB:TMP2, TAB:TMP1->metatable
   |  ld TMP0, CFUNC:RB->upvalue[0]
   |  bnez TAB:TMP2, ->fff_fallback
@@ -1359,7 +1359,7 @@ static void build_subroutines(BuildCtx *ctx)
   |.ffunc_1 ipairs
   |  checktp TAB:TMP1, CARG1, -LJ_TTAB, ->fff_fallback
   |  ld PC, FRAME_PC(BASE)
-#if LJ_52
+#if LJ_PAIRSMM
   |  ld TAB:TMP2, TAB:TMP1->metatable
   |  ld CFUNC:TMP0, CFUNC:RB->upvalue[0]
   |  bnez TAB:TMP2, ->fff_fallback
diff --git a/src/vm_ppc.dasc b/src/vm_ppc.dasc
index b4260eb..4570c12 100644
--- a/src/vm_ppc.dasc
+++ b/src/vm_ppc.dasc
@@ -1454,7 +1454,7 @@ static void build_subroutines(BuildCtx *ctx)
   |  checktab CARG3
   |   lwz PC, FRAME_PC(BASE)
   |  bne ->fff_fallback
-#if LJ_52
+#if LJ_PAIRSMM
   |   lwz TAB:TMP2, TAB:CARG1->metatable
   |  lfd f0, CFUNC:RB->upvalue[0]
   |   cmplwi TAB:TMP2, 0
@@ -1540,7 +1540,7 @@ static void build_subroutines(BuildCtx *ctx)
   |  checktab CARG3
   |   lwz PC, FRAME_PC(BASE)
   |  bne ->fff_fallback
-#if LJ_52
+#if LJ_PAIRSMM
   |   lwz TAB:TMP2, TAB:CARG1->metatable
   |  lfd f0, CFUNC:RB->upvalue[0]
   |   cmplwi TAB:TMP2, 0
diff --git a/src/vm_x64.dasc b/src/vm_x64.dasc
index 80753e0..2785f68 100644
--- a/src/vm_x64.dasc
+++ b/src/vm_x64.dasc
@@ -1391,7 +1391,7 @@ static void build_subroutines(BuildCtx *ctx)
   |  mov TAB:RB, [BASE]
   |  mov TMPR, TAB:RB
   |  checktab TAB:RB, ->fff_fallback
-#if LJ_52
+#if LJ_PAIRSMM
   |  cmp aword TAB:RB->metatable, 0; jne ->fff_fallback
 #endif
   |  mov CFUNC:RD, [BASE-16]
@@ -1460,7 +1460,7 @@ static void build_subroutines(BuildCtx *ctx)
   |  mov TAB:RB, [BASE]
   |  mov TMPR, TAB:RB
   |  checktab TAB:RB, ->fff_fallback
-#if LJ_52
+#if LJ_PAIRSMM
   |  cmp aword TAB:RB->metatable, 0; jne ->fff_fallback
 #endif
   |  mov CFUNC:RD, [BASE-16]
diff --git a/src/vm_x86.dasc b/src/vm_x86.dasc
index 56bee14..eae07f7 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_PAIRSMM
   |  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_PAIRSMM
   |  cmp dword TAB:RB->metatable, 0; jne ->fff_fallback
 #endif
   |  mov CFUNC:RB, [BASE-8]
diff --git a/test/mmpairs.test.lua b/test/mmpairs.test.lua
new file mode 100755
index 0000000..bb9835d
--- /dev/null
+++ b/test/mmpairs.test.lua
@@ -0,0 +1,50 @@
+#!/usr/bin/env tarantool
+
+tap = require('tap')
+
+test = tap.test("PAIRSMM-is-set")
+test:plan(2)
+
+-- There is no Lua way to detect whether LJ_PAIRSMM is enabled. However, in
+-- tarantool build it's enabled by default. So the test scenario is following:
+-- while we can overload the pairs/ipairs behaviour via metamethod as designed
+-- in Lua 5.2, os.execute still preserves the Lua 5.1 interface.
+
+local mt = {
+	__pairs = function(self)
+            local function stateless_iter(tbl, k)
+                local v
+                k, v = next(tbl, k)
+                while k and v > 0 do k, v = next(tbl, k) end
+                if v then return k,v end
+            end
+        return stateless_iter, self, nil
+        end,
+        __ipairs = function(self)
+            local function stateless_iter(tbl, k)
+                local v
+                k, v = next(tbl, k)
+                while k and v < 0 do k, v = next(tbl, k) end
+                if v then return k,v end
+            end
+        return stateless_iter, self, nil
+        end
+}
+
+local t = setmetatable({ }, mt)
+t[1]  = 10
+t[2]  = 20
+t[3] = -10
+t[4] = -20
+
+local pairs_res = 0
+local ipairs_res = 0
+for k, v in pairs(t) do
+    pairs_res = v + pairs_res
+end
+for k, v in ipairs(t) do
+    ipairs_res = v + ipairs_res
+end
+test:is(pairs_res + ipairs_res, 0)
+os_exec_res = os.execute()
+test:is(os_exec_res, 1)
-- 
2.20.1 (Apple Git-117)

Re: [Tarantool-patches] [PATCH v5] build: introduce LUAJIT_ENABLE_PAIRSMM flag

[Cyrill Gorcunov]

On Tue, Nov 26, 2019 at 05:48:37PM +0300, Olga Arkhangelskaia wrote:
...
> +
> +-- There is no Lua way to detect whether LJ_PAIRSMM is enabled. However, in
> +-- tarantool build it's enabled by default. So the test scenario is following:
> +-- while we can overload the pairs/ipairs behaviour via metamethod as designed
> +-- in Lua 5.2, os.execute still preserves the Lua 5.1 interface.
> +
> +local mt = {
> +	__pairs = function(self)
> +            local function stateless_iter(tbl, k)
> +                local v
> +                k, v = next(tbl, k)
> +                while k and v > 0 do k, v = next(tbl, k) end
> +                if v then return k,v end
> +            end

Olga, could you please fix indentation. AFAIU we tend to use
4-space tabs for lua code. Don't we? Same applies to the
code below which I've just stripped out to be short.

Re: [Tarantool-patches] [PATCH v5] build: introduce LUAJIT_ENABLE_PAIRSMM flag

[Igor Munkin]

Olya,

Thanks for the changes. This patch is already applied so I will adjust
the naming by myself in a separate patch. Nevermind.

-- 
Best regards,
IM

Re: [Tarantool-patches] [PATCH v5] build: introduce LUAJIT_ENABLE_PAIRSMM flag

[Konstantin Osipov]

* Olga Arkhangelskaia <arkholga@tarantool.org> [19/11/26 17:52]:
> Adds LUAJIT_ENABLE_PAIRSMM flag as a build option for luajit.
> If the flag is set, pairs/ipairs metamethods are available in Lua 5.1.
> For tarantool this option is enabled by default.
> 
> Part of #4560
> Branch:https://github.com/tarantool/luajit/tree/OKriw/gh-4560-Enable-LUAJIT_ENABLE_LUA52COMPAT-when-bulding-luajit
> 
> v1: https://lists.tarantool.org/pipermail/tarantool-patches/2019-November/012466.html
> v2: https://lists.tarantool.org/pipermail/tarantool-patches/2019-November/012489.html
> v3: https://lists.tarantool.org/pipermail/tarantool-patches/2019-November/012527.html
> 
> Changes in v2:
> - flag is renamed
> - now flag is used only for pairsmm
> - added test case
> Changes in v3:
> - added flag to other vm*
> - changed comments and commit msg
> Changes in v4:
> - fixed errors in arm/arm64 vm
> - rewrited commit msg, subject, comment 
> 
> Changes in v5:
> - fixed test name

It's nice there are so many changes, but usually they are from
newest to oldest, not from oldest to newest.


-- 
Konstantin Osipov, Moscow, Russia

Re: [Tarantool-patches] [PATCH v5] build: introduce LUAJIT_ENABLE_PAIRSMM flag

[Kirill Yukhin]

Hello,

On 26 ноя 17:48, Olga Arkhangelskaia wrote:
> Adds LUAJIT_ENABLE_PAIRSMM flag as a build option for luajit.
> If the flag is set, pairs/ipairs metamethods are available in Lua 5.1.
> For tarantool this option is enabled by default.
> 
> Part of #4560
> Branch:https://github.com/tarantool/luajit/tree/OKriw/gh-4560-Enable-LUAJIT_ENABLE_LUA52COMPAT-when-bulding-luajit
> 
> v1: https://lists.tarantool.org/pipermail/tarantool-patches/2019-November/012466.html
> v2: https://lists.tarantool.org/pipermail/tarantool-patches/2019-November/012489.html
> v3: https://lists.tarantool.org/pipermail/tarantool-patches/2019-November/012527.html

This change breaks compatibility w/ Lua 5.1
and was checked into 1.10, 2.1, 2.2, 2.3 and master
by mistake.
Right it leads to failures in existing Lua code
(see tarantool/tarantool#4770).

The change was reverted in 1.10, 2.2, 2.3 and master.

--
Regards, Kirill Yukhin