XMMatrixRotationRollPitchYaw

Can someone explain why matrices m1 and m2 are not the same, and what m1 is actually doing since m1 is even different from m3?

According to msdn:

XMMatrixRotationRollPitchYaw receives the following parameters pitch -> yaw -> roll (formal parameter order),

which represents rotation around x -> y -> z (formal parameter order),

which is applied as roll -> pitch -> yaw (matrix multiplication order),

which represents rotation around z -> x -> y (matrix multiplication order).

So transformation matrix T = Ry * Rx * Rz = Ry * Rx (matrix m2), transforms a vector v as Tv.

XMFLOAT4X4 m1, m2, m3;
DirectX::XMStoreFloat4x4(&m1, XMMatrixRotationRollPitchYaw(XM_PIDIV4, XM_PIDIV2, 0.0f));
DirectX::XMStoreFloat4x4(&m2, XMMatrixRotationY(XM_PIDIV2) * XMMatrixRotationX(XM_PIDIV4));
DirectX::XMStoreFloat4x4(&m3, XMMatrixRotationX(XM_PIDIV4) * XMMatrixRotationY(XM_PIDIV2));