5 ms·

So you mean having two executables in one? A la Apple "fat executables"?

• davidcuddeback 9y ago
  Probably something like a table of function pointers for "hot" code that gets setup at program start. But compiler writers are way more clever than I am at this sort of thing, so I'm actually curious what solutions they came up with.
• jabl 9y ago
  No, it's on a per-function basis. On program startup it does the necessary checks (CPUID etc.) and sets up the function pointers appropriately (see the IFUNC mechanism in the linker). See e.g. https://lwn.net/Articles/691932/ https://lwn.net/Articles/691932/
  • davidcuddeback 9y ago
    Thanks! I was trying to find some information on this, but didn't know the right search terms.
  • faragon 9y ago
    That's OK for code e.g. you know it could benefit from SIMD usage. However you can not tag every function of user code for safe/unsafe mode. Also, optimizations would increase the mess (inlining, unrolling, etc.). Generated code would be a "Frankenstein".
• deleted 9y ago
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