Hi Ard, On Mon, Oct 7, 2019 at 6:46 PM Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > Arnd reports that the 32-bit generic library code for Curve25119 ends > up using an excessive amount of stack space when built with Clang: > > lib/crypto/curve25519-fiat32.c:756:6: error: stack frame size > of 1384 bytes in function 'curve25519_generic' > [-Werror,-Wframe-larger-than=] > > Let's give some hints to the compiler regarding which routines should > not be inlined, to prevent it from running out of registers and spilling > to the stack. The resulting code performs identically under both GCC > and Clang, and makes the warning go away. Are you *sure* about that? Couldn't we fix clang instead? I'd rather fixes go there instead of gimping this. The reason is that I noticed before that this code, performance-wise, was very inlining sensitive. Can you benchmark this on ARM32-noneon and on MIPS32? If there's a performance difference there, then maybe you can defer this part of the series until after the rest lands, and then we'll discuss at length various strategies? Alternatively, if you benchmark those and it also makes no difference, then it indeed makes no difference. Jason
