Re: Major bug with JIT loop compiling
- From: Leo Razoumov <slonik.az@xxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Sat, 20 Oct 2012 18:54:04 -0400
On Sat, Oct 20, 2012 at 1:08 PM, Declan White <deco.da.man@xxxxxxxxx> wrote:
> Howdy,
>
> Either I've gone crazy, or the JIT compiler has a major problem.
>
> local upvalue
>
> function test()
> local last
> for j = 1, 20 do
> last = upvalue
> end
> print(last, upvalue)
> end
>
> for i = 1, 8 do
> upvalue = i
> test()
> end
>
>
> When this code is run with JIT enabled (independent of optimisation flags),
> it produces the following output:
>
> LuaJIT 2.0.0-beta11 (Linux x64)
> JIT: ON CMOV SSE2 SSE3 SSE4.1
> 1 1
> 2 2
> 3 3
> 3 4
> 3 5
> 3 6
> 3 7
> 3 8
>
>
> Which is – as I'm sure you can tell – definitely not correct.
>
> Lua 5.1
> 1 1
> 2 2
> 3 3
> 4 4
> 5 5
> 6 6
> 7 7
> 8 8
>
>
> It also occurs on Windows x64 and Windows x86, and I've tested back to
> beta10, July 30.
>
> I have a sneaking suspicion that I've done seriously wrong... how could such
> a major bug go unfound for so long?
> (If this is intentional, it's definitely not expected!)
> This is my reduced use case: http://codepad.org/XH81xmZm
>
I see the same behavior with LuaJIT-2.0.beta10 (git HEAD as of
2012-09-16, hash=ead325b0c9) on Linux x86.
Nasty, indeed!
--Leo--
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