Tomasz Kaminski [Monday, 20 October 2025, 16:19:02 CEST]: > If the bug is in libstdc++ or a wrong-code bug in GCC, then yes, this is a > > > problem. If the bug is in the user's code, then what difference does it > > make? > > I assume there is a possibility of situations when builtins will fail, but > element-wise > code will work. For example when someone uses misaligned simd object, that > was > reinterpret casted from chunk of memory. > In that case, the problem will disappear for non-optimized code.
That's hard to say. It can go both ways. But typically the non-constprop code would call a builtin, which is translated into a SIMD instruction, which then (might) require an aligned load address. The const-prop branch on the other might eliminate the SIMD instruction altogether and not crash. Misalignment crashes are best debugged in -O2 anyway. (But that doesn't change any of what you said, I know.) > Anyway, I am not asking you to remove it completely, just centralize the > checks to one place. I'm not objecting to that. I just wanted to add my perspective of the issue. -- ────────────────────────────────────────────────────────────────────────── Dr. Matthias Kretz https://mattkretz.github.io GSI Helmholtz Center for Heavy Ion Research https://gsi.de std::simd ──────────────────────────────────────────────────────────────────────────
