mirror of
https://github.com/LuaJIT/LuaJIT.git
synced 2025-02-08 23:44:08 +00:00
Mirror of the LuaJIT git repository
33ee12a91b
The assertion logic is the only thing actually changing within `lj_ir_kptr_`: the existing `mref` / `setmref` invocations already deal in zero-extended pointers rather than sign-extended pointers. Perhaps surprisingly, the logic around continuation pointers is changing. To appreciate why, the following cryptic comment from vm_x86.dasc comes into play: ``` |->cont_dispatch: ... | movsxd RAa, dword [RB-16] // May be negative on WIN64 with debug. ``` Namely, when using MSVC in debug mode, function symbols with external linkage are subject to extra jump stubs in order to support incremental linking. For example, these jump stubs might look like: ``` ... lj_bcwrite: 07FFC47A5EF23 jmp lj_bcwrite (07FFC47AB5750h) lj_cont_ra: 07FFC47A5EF28 jmp lj_cont_ra (07FFC47A6230Dh) lj_ir_call: 07FFC47A5EF2D jmp lj_ir_call (07FFC47AF6310h) lj_cconv_tv_bf: 07FFC47A5EF32 jmp lj_cconv_tv_bf (07FFC47AC1EA0h) ... ``` When continutation pointers are formed, it is e.g. 07FFC47A5EF28 rather than 07FFC47A6230 from which lj_vm_asm_begin gets subtracted, and it can be the case that 07FFC47A5EF28 is less than lj_vm_asm_begin. Consequently, this could previously result in continuation pointers in range [-2G, 0). (The eagle-eyed reader might think that lj_vm_asm_begin is also a function symbol with external linkage, but buildvm is careful to define it as a data symbol rather than a function symbol). This change was actually motivated by an assertion failure in WIN64 debug mode (wherein `snap_replay_const` does `lj_ir_kptr(J, ir_kptr(ir))`, as `ir_kptr` performs zero-extension, and then `lj_ir_kptr` would barf), but given the recent block allocator change to support the [0, 4G) address range on (non-x64) 64-bit platforms, the change seems prudent for other reasons too. |
||
|---|---|---|
| doc | ||
| dynasm | ||
| etc | ||
| src | ||
| .gitignore | ||
| COPYRIGHT | ||
| Makefile | ||
| README | ||
README for LuaJIT 2.1.0-beta2 ----------------------------- LuaJIT is a Just-In-Time (JIT) compiler for the Lua programming language. Project Homepage: http://luajit.org/ LuaJIT is Copyright (C) 2005-2016 Mike Pall. LuaJIT is free software, released under the MIT license. See full Copyright Notice in the COPYRIGHT file or in luajit.h. Documentation for LuaJIT is available in HTML format. Please point your favorite browser to: doc/luajit.html