Need Programmer's Reference Manual TI Stellaris LM4F120H5QR
TI rebranded the Stellaris LM4F120 part as the Tiva TM4C123 part.  They're nearly identical and the documentation, driver software, and example code is mostly interchangeable.  They both use an ARM Cortex-M4 core.  When I want to learn details about core instructions I check the ARM documentation, Cortex-M4 Instruction Set