CONFIG_ISA_THUMB2

From: http://www.arm.com/products/processors/technologies/instruction-set-architectures.php

Thumb-2 technology is the instruction set underlying the ARM Cortex architecture which provides enhanced levels of performance, energy efficiency, and code density for a wide range of embedded applications.

Thumb-2 technology builds on the success of Thumb, the innovative high code density instruction set for ARM microprocessor cores, to increase the power of the ARM microprocessor core available to developers of low cost, high performance systems.

The technology is backwards compatible with existing ARM and Thumb solutions, while significantly extending the features available to the Thumb instructions set. This allows more of the application to benefit from the best in class code density of Thumb.

For performance optimised code Thumb-2 technology uses 31 percent less memory to reduce system cost, while providing up to 38 percent higher performance than existing high density code, which can be used to prolong battery-life or to enrich the product feature set. Thumb-2 technology is featured in the processor, and in all ARMv7 architecture-based processors.