Extremely slow Clang + Valgrind on macOS x86_64 #1757

1. 
   hebasto commented at 8:25 pm on October 14, 2025: member

   The “x86_64: macOS Ventura, Valgrind (clang)” CI job takes more than 40 min:

   • https://github.com/bitcoin-core/secp256k1/actions/runs/18495253559/job/52697859721
   • https://github.com/bitcoin-core/secp256k1/actions/runs/18507649867/job/52740457457

   However, “x86_64: macOS Ventura, Valgrind (gcc)” takes less than 20 min:

   • https://github.com/bitcoin-core/secp256k1/actions/runs/18495253559/job/52697859732
   • https://github.com/bitcoin-core/secp256k1/actions/runs/18507649867/job/52740457434
2. 
   real-or-random commented at 6:45 am on October 15, 2025: contributor

   Hm, interesting observation. But for now, I’d assume it’s legitimate? Perhaps, for some reason, clang’s output has much more of what slows down Valgrind (e.g., direct memory accesses instead of calls to intercepted functions such as memcpy).

   I’m not convinced that we should do anything about it right now. This will be resolved by #1755. If it turns out to be an issue on future Valgrind macOS jobs, we could still check which of the tests are slow. The new framework (#1734) makes this much easier.

3. real-or-random added the label ci on Oct 15, 2025
4. real-or-random added the label performance on Oct 15, 2025
5. 
   real-or-random commented at 7:08 am on October 17, 2025: contributor

   Unfortunately, #1759 hasn’t improved this.

   clang, slow: https://github.com/bitcoin-core/secp256k1/actions/runs/18569028464/job/52937855454?pr=1759 gcc, fast: https://github.com/bitcoin-core/secp256k1/actions/runs/18569028464/job/52937855452?pr=1759

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hebasto real-or-random

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ci performance