Comment by stevefan1999
3 hours ago
It would be cool if we can use LLVM to lift the x86 code into LLVM bitcode and go to different platforms easily with ostate of the art optimizations, won't it?
3 hours ago
It would be cool if we can use LLVM to lift the x86 code into LLVM bitcode and go to different platforms easily with ostate of the art optimizations, won't it?
Been there, done that during my PhD (code: [1]). Works reasonably well, except for compile times (for which I implemented a caching strategy). However, due to calling conventions, using LLVM isn't going to give the best possible performance. Some features like signal handling are extremely hard to implement with LLVM (I didn't, therefore). Although the overall performance results have been good, it's not an approach that I could strongly recommend.
[1]: https://github.com/aengelke/instrew
Sadly compile times of LLVM-based recompilers make it impractical for competitive x86 emulation. We're not just talking a few single-frame stutters here and there, but considerable startup delays and pauses in-game.
LLVM's optimization passes also are less useful than you might think, since the vast majority of them is motivated by source->binary translation (like clang). They don't have much effect when recompiling an already optimized binary to another architecture.