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Confidential
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Thumb Instruction Set
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Thumb is a 16-bit instruction set
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Optimized for code density from C code (~65% of ARM code size)
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Improved performance from narrow memory
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Subset of the functionality of the ARM instruction set
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Thumb is not a “regular” instruction set!
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Constraints are not generally consistent
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Targeted at compiler generation, not hand coding
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Thumb-2 Instruction Set
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Thumb-2 is a major extension to the Thumb ISA
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Adds 32-bit instructions to implement almost all of the ARM ISA functionality
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Retains the complete 16-bit Thumb instruction set
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Design objective: ARM performance with Thumb code density
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No switching between ARM-Thumb states
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Compiler automatically selects mix of 16 and 32 bit instructions
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