JojoR via Gcc <gcc@gcc.gnu.org> writes: > Hi, > > I have a little know about for 'Sizes and offsets as runtime > invariants’, > > and need to add vector types like V2SImode as compile-time constants > with enabled vector types of runtime invariants. > > Could I enable two vector types at same time ? > I guess it’s not allow :( > > Could anyone give me some hints ?
Vector modes like V2SI always represent fixed-length vectors. Variable-length vector modes have to be defined explicitly in the .def file. A target can have both variable-length and fixed-length vectors. Probably the best place to look for examples is the aarch64 backend. There we have: - V2SI (64-bit Advanced SIMD) - V4SI (128-bit Advanced SIMD) - VNx2SI (variable-length SVE vector with 2 32-bit elements per 128-bit granule) - VNx4SI (variable-length SVE vector with 4 32-bit elements per 128-bit granule) etc. In target-independent code, things like GET_MODE_NUNITS are always poly_ints. In other words, the number of elements might be constant (is_constant()) or might vary at runtime (!is_constant()). On targets like x86 that don't define variable-length vectors, things like GET_MODE_NUNITS are always compile-time constants *within config/i386*. This removes the need to use is_constant() everywhere. On targets like aarch64 that do define variable-length vectors, things like GET_MODE_NUNITS are poly_ints even in config/aarch64. However, GET_MODE_NUNITS is still constant for V2SI and V4SI. We just have to use to_constant() to get the constant 2 or 4. Thanks, Richard
