ICE: intrinsic with vector arguments

[JohanEngelen]

Testcase that segfaults:

import core.simd;

pragma(LDC_intrinsic, "llvm.fshl.i#")
    T llvm_fshl(T)(T a, T b, T shift)
        if (__traits(isIntegral, T));

int4 rotateLeftIntrinsic(int4 x, int4 bits) {
    return llvm_fshl(x, x, bits);
}

https://d.godbolt.org/z/XUvSX9

Apparently vector types pass the isIntegral test. At the least, we shouldn't crash on this.