[Tarantool-patches] [PATCH luajit 2/2] Fix maxslots when recording BC_VARG, part 2.

[Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

From: Mike Pall <mike>

Analyzed by Sergey Kaplun.

(cherry-picked from commit a01cba9d2d74efc57376822aa43db2d5043af5a4)

This patch is the follow-up for the previous one. It removes the
condition for `maxslot` changing in the case when varargs are defined
on the trace (i.e. `framedepth` > 0).

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

Part of tarantool/tarantool#8825
---
 src/lj_record.c                               |  8 ++------
 .../lj-1024-varg-maxslot.test.lua             | 19 ++++++++++++++++++-
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/lj_record.c b/src/lj_record.c
index 112524d3..02d9db9e 100644
--- a/src/lj_record.c
+++ b/src/lj_record.c
@@ -1775,12 +1775,8 @@ static void rec_varg(jit_State *J, BCReg dst, ptrdiff_t nresults)
   if (J->framedepth > 0) {  /* Simple case: varargs defined on-trace. */
     ptrdiff_t i;
     if (nvararg < 0) nvararg = 0;
-    if (nresults == -1) {
-      nresults = nvararg;
-      J->maxslot = dst + (BCReg)nvararg;
-    } else if (dst + nresults > J->maxslot) {
-      J->maxslot = dst + (BCReg)nresults;
-    }
+    if (nresults == -1) nresults = nvararg;
+    J->maxslot = dst + (BCReg)nresults;
     for (i = 0; i < nresults; i++)
       J->base[dst+i] = i < nvararg ? getslot(J, i - nvararg - 1 - LJ_FR2) : TREF_NIL;
   } else {  /* Unknown number of varargs passed to trace. */
diff --git a/test/tarantool-tests/lj-1024-varg-maxslot.test.lua b/test/tarantool-tests/lj-1024-varg-maxslot.test.lua
index 14270595..f8d74e8a 100644
--- a/test/tarantool-tests/lj-1024-varg-maxslot.test.lua
+++ b/test/tarantool-tests/lj-1024-varg-maxslot.test.lua
@@ -3,7 +3,7 @@ local test = tap.test('lj-noticket-varg-usedef'):skipcond({
   ['Test requires JIT enabled'] = not jit.status(),
 })
 
-test:plan(1)
+test:plan(2)
 
 jit.opt.start('hotloop=1')
 
@@ -20,4 +20,21 @@ end
 
 test:ok(true, 'BC_VARG recording 0th frame depth')
 
+-- Now the same case, but with additional frame, so VARG slots
+-- are defined on the trace.
+local function bump_varg_frame(...)
+  -- BC_VARG 1 1 0. `...` is nil (argument for the script).
+  -- luacheck: ignore
+  -- XXX: some condition to use several slots on the Lua stack.
+  anchor = 1 >= 1, ...
+end
+
+counter = 0
+while counter < 3 do
+  counter = counter + 1
+  bump_varg_frame()
+end
+
+test:ok(true, 'BC_VARG recording with defined on trace VARG slots')
+
 os.exit(test:check() and 0 or 1)
-- 
2.34.1