On Mon, 14 Jul 2025, Imple Lee via Gcc-help wrote: > I'm writing code about gcc vector types, which, in C, looks like this. > > ```C > typedef int v4si __attribute__ ((vector_size (16))); > ``` > > The relevant documentation is as follows. > > > The result of the comparison is a vector of the same width and number of elements as the comparison operands with a signed integral element type. > > However, on architectures where different integral types have the same > width, e.g. `long` and `long long` are both 64-bit on x86-64 linux, it > is unclear which type will be used (on x86-64 linux, the type of both > `vector of long == vector of long` and `vector of long long == vector > of long long` are both `vector of long`). Are there any more specific > rules in such cases? Since I want to support many different > architectures, experimenting on all of them to find the rule seems > kind of tedious... Unfortunately, Clang and GCC implement different rules here, so perhaps it would be best to avoid a dependency on that, if possible?.. For GCC, element type for the resulting vector is chosen in c_common_type_for_size, which starts by picking a suitable type in sequence int, signed char, short, long, long long. Hence, 'long' is never chosen on ILP32 platforms, and 'long long' won't be picked on LP64. https://gcc.gnu.org/cgit/gcc/tree/gcc/c-family/c-common.cc#n2339 HTH Alexander
