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Is there any particular reason for LLVM being slow? Does it do a lot of complicated optimizations when generating code, or is it designed in a way that makes it
by jfim 3y ago
Is there any particular reason for LLVM being slow? Does it do a lot of complicated optimizations when generating code, or is it designed in a way that makes it slow?
- loup-vaillant 3y agoI’ve heard it used to be lean and fast. Then new developers came in, new features were implemented, and it bloated over time. Thus it wasn’t designed in a way that makes it slow. It grew in a way that makes it slow. Source: hearsay.
- foofie 3y ago> I’ve heard it used to be lean and fast. Then new developers came in, new features were implemented, and it bloated over time. That's basically the story of every single software project ever made.
- pjmlp 3y agoNot only that, at the end of ISO C++ Standards Committee Panel Discussion, https://www.youtube.com/watch?v=sf_3Vfh6yRA https://www.youtube.com/watch?v=sf_3Vfh6yRA Someone from the panel clearly mentions that clang and GCC have become slower as some big names have removed their support from the projects (most likely meaning Apple and Google).
- marckerbiquet 3y agoA possible reason is the use of Static Single Assignment (SSA). While it makes many optimizations easier, it has to translate its IR out-of-SSA to generate code. This is very expensive as it needs computation of dominance on the Control Flow Graph, insert copies and much more. But it's just a guess.