[Tarantool-patches] [PATCH] fold: keep type of emitted CONV in sync with its mode

[Sergey Ostanevich]

Hi!

Thanks for the patch, I didn't find any similar issues to fix along with
it.

LGTM,
Sergos

On 02 Dec 10:03, Igor Munkin wrote:
> From: Vyacheslav Egorov <vegorov at google.com>
> 
> When emitting CONV make sure that its type matches its destination IRType.
> 
> This keeps IR fully internally consistent with respect to types - i.e. if
> we push narrowing CONV Dt.St upwards through an arithmetic operation of type
> St we end up with arithmetic operation of type Dt and two convertions
> CONV Dt.St which narrow the operands.
> 
> Igor Munkin:
> * added a test for the problem
> * backported the original patch to tarantool/luajit repo
> * stripped some words not related to the patch itself
> 
> Fixes LuaJIT/LuaJIT#524
> 
> Signed-off-by: Vyacheslav Egorov <vegorov at google.com>
> Signed-off-by: Igor Munkin <imun at tarantool.org>
> ---
> 
> This is a backport for https://github.com/moonjit/moonjit/commit/4dba12d
> 
> Branch: https://github.com/tarantool/luajit/tree/imun/backport-fix-LuaJIT-524
> Issue: https://github.com/LuaJIT/LuaJIT/issues/524
> 
>  src/lj_opt_fold.c                 |  4 ++--
>  test/fold_bug_LuaJIT_524.test.lua | 24 ++++++++++++++++++++++++
>  2 files changed, 26 insertions(+), 2 deletions(-)
>  create mode 100755 test/fold_bug_LuaJIT_524.test.lua
> 
> diff --git a/src/lj_opt_fold.c b/src/lj_opt_fold.c
> index acbf36a..3c50806 100644
> --- a/src/lj_opt_fold.c
> +++ b/src/lj_opt_fold.c
> @@ -1261,8 +1261,8 @@ LJFOLDF(simplify_conv_narrow)
>    IRType t = irt_type(fins->t);
>    IRRef op1 = fleft->op1, op2 = fleft->op2, mode = fins->op2;
>    PHIBARRIER(fleft);
> -  op1 = emitir(IRTI(IR_CONV), op1, mode);
> -  op2 = emitir(IRTI(IR_CONV), op2, mode);
> +  op1 = emitir(IRT(IR_CONV, t), op1, mode);
> +  op2 = emitir(IRT(IR_CONV, t), op2, mode);
>    fins->ot = IRT(op, t);
>    fins->op1 = op1;
>    fins->op2 = op2;
> diff --git a/test/fold_bug_LuaJIT_524.test.lua b/test/fold_bug_LuaJIT_524.test.lua
> new file mode 100755
> index 0000000..b056684
> --- /dev/null
> +++ b/test/fold_bug_LuaJIT_524.test.lua
> @@ -0,0 +1,24 @@
> +#!/usr/bin/env tarantool
> +
> +local tap = require('tap')
> +local ffi = require('ffi')
> +
> +local test = tap.test("LuaJIT 524")
> +test:plan(1)
> +
> +-- Test file to demonstrate LuaJIT folding machinery incorrect behaviour,
> +-- details:
> +--     https://github.com/LuaJIT/LuaJIT/issues/524
> +--     https://github.com/moonjit/moonjit/issues/37
> +
> +jit.opt.start(0, "fold", "cse", "fwd", "hotloop=1")
> +
> +local sq = ffi.cast("uint32_t", 42)
> +
> +for _ = 1, 3 do
> +    sq = ffi.cast("uint32_t", sq * sq)
> +end
> +
> +test:is(tonumber(sq), math.fmod(math.pow(42, 8), math.pow(2, 32)))
> +
> +test:check()
> -- 
> 2.24.0
>