[Tarantool-patches] [PATCH luajit] DUALNUM: Add missing type conversion for FORI slots.

[Tarantool-patches] [PATCH luajit] DUALNUM: Add missing type conversion for FORI slots.

[Sergey Kaplun via Tarantool-patches]

From: Mike Pall <mike>

Reported by Sergey Kaplun.

(cherry picked from commit 406cf69b3ae0a3ecd5ede2bb97b937b7a5d92074)

`rec_for_loop()` narrows the FORL index values by getting them from the
runtime. In case when the `start`, `stop`, `step` control variables are
already loaded to the slots, their TRef isn't converted to the
corresponding type. This leads to the following inconsistent IR dump and
to the assertion failure later:
| 0002 > int SLOAD  10   TCI
| 0003   int ADD    0002  +1.
| 0004 > int LE     0003  +1.
| 0005   int ADD    0003  +1.
| 0006 > int GT     0005  +1.

This patch adds the missing type conversion.

Sergey Kaplun:
* added the description and the test for the problem

Part of tarantool/tarantool#12134
---

Branch: https://github.com/tarantool/luajit/tree/skaplun/lj-1413-missing-conv-fori
Related issues:
* https://github.com/LuaJIT/LuaJIT/issues/1413
* https://github.com/tarantool/tarantool/issues/12134

 src/lj_record.c                               | 25 +++++++----
 .../lj-1413-missing-conv-fori.test.lua        | 43 +++++++++++++++++++
 2 files changed, 60 insertions(+), 8 deletions(-)
 create mode 100644 test/tarantool-tests/lj-1413-missing-conv-fori.test.lua

diff --git a/src/lj_record.c b/src/lj_record.c
index ba409a61..abb6334a 100644
--- a/src/lj_record.c
+++ b/src/lj_record.c
@@ -365,12 +365,27 @@ static TRef fori_load(jit_State *J, BCReg slot, IRType t, int mode)
 		mode + conv);
 }
 
+/* Convert FORI argument to expected target type. */
+static TRef fori_conv(jit_State *J, TRef tr, IRType t)
+{
+  if (t == IRT_INT) {
+    if (!tref_isinteger(tr))
+      return emitir(IRTGI(IR_CONV), tr, IRCONV_INT_NUM|IRCONV_CHECK);
+  } else {
+    if (!tref_isnum(tr))
+      return emitir(IRTN(IR_CONV), tr, IRCONV_NUM_INT);
+  }
+  return tr;
+}
+
 /* Peek before FORI to find a const initializer. Otherwise load from slot. */
 static TRef fori_arg(jit_State *J, const BCIns *fori, BCReg slot,
 		     IRType t, int mode)
 {
   TRef tr = J->base[slot];
-  if (!tr) {
+  if (tr) {
+    tr = fori_conv(J, tr, t);
+  } else {
     tr = find_kinit(J, fori, slot, t);
     if (!tr)
       tr = fori_load(J, slot, t, mode);
@@ -517,13 +532,7 @@ static LoopEvent rec_for(jit_State *J, const BCIns *fori, int isforl)
       lj_assertJ(tref_isnumber_str(tr[i]), "bad FORI argument type");
       if (tref_isstr(tr[i]))
 	tr[i] = emitir(IRTG(IR_STRTO, IRT_NUM), tr[i], 0);
-      if (t == IRT_INT) {
-	if (!tref_isinteger(tr[i]))
-	  tr[i] = emitir(IRTGI(IR_CONV), tr[i], IRCONV_INT_NUM|IRCONV_CHECK);
-      } else {
-	if (!tref_isnum(tr[i]))
-	  tr[i] = emitir(IRTN(IR_CONV), tr[i], IRCONV_NUM_INT);
-      }
+      tr[i] = fori_conv(J, tr[i], t);
     }
     tr[FORL_EXT] = tr[FORL_IDX];
     stop = tr[FORL_STOP];
diff --git a/test/tarantool-tests/lj-1413-missing-conv-fori.test.lua b/test/tarantool-tests/lj-1413-missing-conv-fori.test.lua
new file mode 100644
index 00000000..ba1fa74a
--- /dev/null
+++ b/test/tarantool-tests/lj-1413-missing-conv-fori.test.lua
@@ -0,0 +1,43 @@
+local tap = require('tap')
+
+-- Test file to demonstrate LuaJIT incorrect recording of FORI
+-- bytecode in the DUALNUM mode.
+-- See also: https://github.com/LuaJIT/LuaJIT/issues/1413.
+
+local test = tap.test('lj-1413-missing-conv-fori'):skipcond({
+  ['Test requires JIT enabled'] = not jit.status(),
+})
+
+test:plan(1)
+
+local function always_number(val)
+  -- Trace 3 starts as a side trace for the first one.
+  return tonumber(val) or 1
+end
+
+jit.opt.start('hotloop=1', 'hotexit=1')
+
+-- Compile the root trace with stitching.
+always_number()
+always_number('')
+
+-- An additional loop to evidentiate the issue for x86 arch in the
+-- DUALNUM mode.
+for _ = 1, 2 do
+  -- Use '%' to force number slots.
+  for i = always_number(9 % 1), 1 do
+    -- The resulting IR for the trace 4 is the following:
+    -- | 0002 > int SLOAD  10   TCI
+    -- | 0003   int ADD    0002  +1.
+    -- | 0004 > int LE     0003  +1.
+    -- | 0005   int ADD    0003  +1.
+    -- | 0006 > int GT     0005  +1.
+    --
+    -- The problem is within the type mismatch between the result
+    -- type and the right operand in the IRs.
+    for _ = '9' % i, always_number('') do end -- Trace 4.
+  end
+end
+
+test:ok(true, 'no assertion failure')
+test:done(true)
-- 
2.53.0