All the DSP instructions and documentation can be found on the ARM website.
Here is the latest reference manual for the M4 that has the DSP instructions with cycle times: http://infocenter.arm.com/help/topic/com.arm.doc.ddi0439c/DDI0439C_cortex_m4_r0p1_trm.pdf
And the assembly instructions are described in detail in this document: http://infocenter.arm.com/help/topic/com.arm.doc.dui0553a/DUI0553A_cortex_m4_dgug.pdf
You can also find the ARM CMSIS (Cortex Microcontroller Software Interface Standard) DSP 2.0 Library at http://www.onarm.com/
Regards,
Anthony
