ARM ARM1176JZF-S Manuel d'utilisateur télécharger pdf (Page 7)

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Thumb Instruction Set

Thumb is a 16-bit instruction set

Optimized for code density from C code (~65% of ARM code size)

Improved performance from narrow memory

Subset of the functionality of the ARM instruction set

Thumb is not a “regular” instruction set!

Constraints are not generally consistent

Targeted at compiler generation, not hand coding

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Thumb-2 Instruction Set

Thumb-2 is a major extension to the Thumb ISA

Adds 32-bit instructions to implement almost all of the ARM ISA functionality

Retains the complete 16-bit Thumb instruction set

Design objective: ARM performance with Thumb code density

No switching between ARM-Thumb states

Compiler automatically selects mix of 16 and 32 bit instructions

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ARM ARM1176JZF-S Manuel d'utilisateur Page 7