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{{arm title|Helium (MVE)}}{{arm isa main}} | {{arm title|Helium (MVE)}}{{arm isa main}} | ||
'''Helium''' or '''M-Profile Vector Extension''' ('''MVE''') is an optional vector architectural extension introduced as part of the {{arm|ARMv8.1-M}} architecture. Implementations that include MVE also include the DSP extension. | '''Helium''' or '''M-Profile Vector Extension''' ('''MVE''') is an optional vector architectural extension introduced as part of the {{arm|ARMv8.1-M}} architecture. Implementations that include MVE also include the DSP extension. | ||
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== Overview == | == Overview == | ||
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MVE instructions comes in two distinct flavors: '''MVE-I''' and '''MVE-F''': | MVE instructions comes in two distinct flavors: '''MVE-I''' and '''MVE-F''': | ||
− | * '''MVE-I''' operates on 32-bit, 16-bit, and 8-bit | + | * '''MVE-I''' operates on 32-bit, 16-bit, and 8-bit data types |
* '''MVE-F''' operates on [[half-precision]] and [[single-precision]] [[floating-point]] values | * '''MVE-F''' operates on [[half-precision]] and [[single-precision]] [[floating-point]] values | ||
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=== Registers === | === Registers === | ||
− | MVE defines eight vector registers: '''Q0''' .. '''Q7''' | + | MVE defines eight vector registers: '''Q0''' .. '''Q7'''. In order to maximize area reuse, the eight vector registers are defined as aliases onto the Floating-point Extension register file. There are many vector instructions that can use scalar arguments from the general-purpose register file. This was done in order to reduce pressure on the vector register file. |
:[[File:helium vector reg file alias.svg|500px]] | :[[File:helium vector reg file alias.svg|500px]] | ||
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It's worth noting that the number of beats per cycle is not required to be a constant and is allowed to change at runtime. One important rule associated with a dual-beat system is that they may overlap. In other words, an implementation may execute the last two beats of an operation along with the first two beats of the next vector instruction. | It's worth noting that the number of beats per cycle is not required to be a constant and is allowed to change at runtime. One important rule associated with a dual-beat system is that they may overlap. In other words, an implementation may execute the last two beats of an operation along with the first two beats of the next vector instruction. | ||
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=== Predication/conditional execution === | === Predication/conditional execution === |