On 29 July 2016 at 10:12, Zhongwei Yao zhongwei.yao@linaro.org wrote:
Hi, all, I run into Segment Fault in:
======
x = 0
for i = 1, 100 do x = tostring(i) end
y = "101"
======
And it turns out the JITed code overwrites native stack position at trace head. It can be walked around by set SPS_FIXED to 0.
The JITed code is doing register spill and assuming there is "2 fixed spill slots" (defined by SPS_FIXED). But there seems no "fixed spill slots" in arm64 interpreter implementation. Is it true? Could anyone provide some info of aarch64 frame layout?
Any input will help! Thanks.
I've tried your test case here, and it works ok for me. I added print(x) and print(y) and I get 100 and 101 as expected. Do you have an old tree or some local patches?
I added the SPS_FIXED values very early in the port, but they are only copy-and-pasted, so are quite likely to be wrong. Any investigation you can do is valuable :)
There are a few comments about LuaJIT frame layout in lj_frame.h, but I haven't found any clear explanations about how it really works, and there a few hard-coded constants in the interpreter which may be tied to the frame layout.
Charles