Re: [Tarantool-patches] [PATCH luajit] FFI: Fix recording of union initialization.

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

Hi, Max!
Thanks for the fixes!

LGTM, with a minor reminder below.
I suppose, that Sergey concerned about test name in the `test:ok()`
routine.

On 14.07.23, Maxim Kokryashkin wrote:
> 
> Hi!
> Thanks for the review!
> Added a comment with the test description, the branch is force-pushed.
> Here is the diff for the test description:
> ==============================================
> diff --git a/test/tarantool-tests/lj-128-fix-union-init.test.lua b/test/tarantool-tests/lj-128-fix-union-init.test.lua
> index 6a49cec8..65ba0f28 100644
> --- a/test/tarantool-tests/lj-128-fix-union-init.test.lua
> +++ b/test/tarantool-tests/lj-128-fix-union-init.test.lua
> @@ -10,6 +10,46 @@ test:plan(NITERATIONS)
>  local ffi = require('ffi')
>  local union_type = ffi.typeof('union { uint32_t u; float f; }')
>  
> +-- Before the patch, the `union_type` call resulted in the
> +-- initialization of both the integer and the float members
> +-- of the union, leading to undefined behavior since the
> +-- integer member was overwritten.
> +-- The IR was the following:
> +--
> +-- 0031 ------ LOOP ------------
> +-- 0032    u8  XLOAD  [0x100684521]  V
> +-- 0033    int BAND   0032  +12
> +-- 0034 >  int EQ     0033  +0
> +-- 0035 >  cdt CNEW   +96
> +-- 0036    p64 ADD    0035  +16
> +-- 0037    u32 XSTORE 0036  0029 <--- `u` member init
> +-- 0038    flt XSTORE 0036  0022 <--- `f` member init
> +-- 0039    u32 XLOAD  0036
> +-- 0040    num CONV   0039  num.u32
> +-- 0041    num CONV   0029  num.int
> +-- 0042 >  num EQ     0041  0040
> +-- 0043  + int ADD    0029  +1
> +-- 0044 >  int LE     0043  0001
> +-- 0045    int PHI    0029  0043
> +--
> +-- After the patch, the initialization is performed only
> +-- for the first member of the union, so now IR looks
> +-- like this:
> +-- 0029 ------ LOOP ------------
> +-- 0030    u8  XLOAD  [0x1047c4521]  V
> +-- 0031    int BAND   0030  +12
> +-- 0032 >  int EQ     0031  +0
> +-- 0033 }  cdt CNEW   +96
> +-- 0034    p64 ADD    0033  +16
> +-- 0035 }  u32 XSTORE 0034  0027 <--- `u` member init
> +-- 0036    u32 CONV   0027  u32.int
> +-- 0037    num CONV   0036  num.u32
> +-- 0038    num CONV   0027  num.int
> +-- 0039 >  num EQ     0038  0037
> +-- 0040  + int ADD    0027  +1
> +-- 0041 >  int LE     0040  0001
> +-- 0042    int PHI    0027  0040
> +
>  jit.opt.start('hotloop=1')
>  for i = 1, NITERATIONS do
>    test:ok(union_type(i).u == i)

Minor: the description of the test is still missing.

> ==============================================

<snipped>

> >>> +for i = 1, NITERATIONS do
> >>> + test:ok(union_type(i).u == i)
> >>testcases description is missed, please add one.
> >>> +end
> >>> +
> >>> +os.exit(test:check() and 0 or 1)
> > 

-- 
Best regards,
Sergey Kaplun