Jan Philipp Hafer 1ea650bb75 compiler_rt: add __popcountsi2, __popcountdi2 and __popcountti2
- apply simpler approach than LLVM for __popcountdi2
  taken from The Art of Computer Programming and generalized
- rename popcountdi2.zig to popcount.zig
- test cases derived from popcountdi2_test.zig
- tests: compare naive approach 10_000 times with
  random numbers created from naive seed 42

    See #1290
2021-11-29 12:50:25 -08:00
..
2019-09-25 23:35:41 -04:00

This compiler-rt library is ported from LLVM.

It's needed because LLVM emits library calls to compiler-rt when hardware lacks functionality, for example, 64-bit integer multiplication on 32-bit x86.

This library is automatically built as-needed for the compilation target and then statically linked and therefore is a transparent dependency for the programmer.

Any bugs should be solved by trying to duplicate the bug upstream.

  • If the bug exists upstream, get it fixed with the LLVM team and then port the fix downstream to Zig.
  • If the bug only exists in Zig, something went wrong porting the code, and you can run the C code and Zig code side by side in a debugger to figure out what's happening differently.