[Tarantool-patches] [PATCH luajit] LJ_GC64: Fix IR_VARG offset for fixed number of results.

sergos sergos at tarantool.org
Thu Jul 14 14:54:30 MSK 2022


Hi!

Thanks for the patch, some updates to the test.

Regards,
Sergos

> On 13 Jul 2022, at 12:53, Sergey Kaplun <skaplun at tarantool.org> wrote:
> 
> From: Mike Pall <mike>
> 
> Reported by George Vaintrub. Fixed by Sergey Kaplun.
> 
> (cherry picked from commit 6bda30d8c745b3963ba870221b9be6acdffed9b1)
> 
> This bug occurs when recording `BC_VARG` with the following conditions:
> 1) varargs undefined on trace.
Later in the test you just mention its size should be bigger than results’ one?

> 2) known fixed number of results.
> 
> For this case the vararg slots loads via `IR_VLOAD` by offset from
                                are loaded by       using an

> vararg base. In GC64 mode this offset was miscounting due to missing
the             the                      is miscounted

> `LJ_FR2` correction in the base TRef calculation. As the result the
> wrong (+1) vararg slot is used.
> 
> This patch adds the missing the aforementioned `LJ_FR2` correction.
                              xxx
> 
> Sergey Kaplun:
> * added the description and the test for the problem
> 
> Resolves tarantool/tarantool#7172
> Part of tarantool/tarantool#7230
> ---
> 
> Branch: https://github.com/tarantool/luajit/tree/skaplun/lj-864-varg-rec-base-offset-full-ci
> Issues:
> * https://github.com/tarantool/tarantool/issues/7172
> * https://github.com/LuaJIT/LuaJIT/issues/864
> 
> src/lj_record.c                               |  2 +-
> .../lj-864-varg-rec-base-offset.test.lua      | 25 +++++++++++++++++++
> 2 files changed, 26 insertions(+), 1 deletion(-)
> create mode 100644 test/tarantool-tests/lj-864-varg-rec-base-offset.test.lua
> 
> diff --git a/src/lj_record.c b/src/lj_record.c
> index a11f3712..9e2e1d9e 100644
> --- a/src/lj_record.c
> +++ b/src/lj_record.c
> @@ -1794,7 +1794,7 @@ static void rec_varg(jit_State *J, BCReg dst, ptrdiff_t nresults)
> 	  emitir(IRTGI(IR_EQ), fr,
> 		 lj_ir_kint(J, (int32_t)frame_ftsz(J->L->base-1)));
> 	vbase = emitir(IRT(IR_SUB, IRT_IGC), REF_BASE, fr);
> -	vbase = emitir(IRT(IR_ADD, IRT_PGC), vbase, lj_ir_kint(J, frofs-8));
> +	vbase = emitir(IRT(IR_ADD, IRT_PGC), vbase, lj_ir_kint(J, frofs-8*(1+LJ_FR2)));
                                                                         Wherearemyspaces?
                                                                      (nevermind, just a moan)

> 	for (i = 0; i < nload; i++) {
> 	  IRType t = itype2irt(&J->L->base[i-1-LJ_FR2-nvararg]);
> 	  TRef aref = emitir(IRT(IR_AREF, IRT_PGC),
> diff --git a/test/tarantool-tests/lj-864-varg-rec-base-offset.test.lua b/test/tarantool-tests/lj-864-varg-rec-base-offset.test.lua
> new file mode 100644
> index 00000000..ca30f92f
> --- /dev/null
> +++ b/test/tarantool-tests/lj-864-varg-rec-base-offset.test.lua
> @@ -0,0 +1,25 @@
> +local tap = require('tap')
> +
> +-- Test file to demonstrate LuaJIT misbehaviour during recording
> +-- BC_VARG with nvarargs >= nresults in GC64 mode.
In the message you say it should be unknown. What’s the dirty truth is?

> +-- See also https://github.com/LuaJIT/LuaJIT/issues/864,
> +-- https://github.com/tarantool/tarantool/issues/7172.
> +local test = tap.test('lj-864-varg-rec-base-offset')
> +test:plan(1)
> +
> +jit.opt.start('hotloop=1')
> +
> +local MAGIC = 42
Should be enough to test against the first argument, no MAGIC :)

> +local function test_rec_varg(...)
> +  local slot1
> +  for _ = 1, 3 do
> +    slot1 = ...
> +  end
++  args = {...}
+-  return slot1 == args[1]
> +end
> +
> +-- Test case for nvarargs >= nresults. Equality is not suitable
> +-- due to failing assertion guard for type of loaded vararg slot.
> +test:ok(test_rec_varg(MAGIC, 0), 'correct BC_VARG recording')
> +
> +os.exit(test:check() and 0 or 1)
> -- 
> 2.34.1
> 



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