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40 lines
1.3 KiB
Markdown
40 lines
1.3 KiB
Markdown
# Section 2 / Registers (Simplified)
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## Overview
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There are four highest level ideas relating to floating point operations
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on AARCH64.
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* There is another complete register set for floating point values.
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* There are alternative instructions just for floating point values.
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* There are exotic instructions that operate on sets of floating point
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values (SIMD).
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* There are instructions to go back and forth to and from the integer
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registers.
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## Floating Point Registers
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There will be a more detailed discussion of the floating point registers
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when exotic instructions such as SIMD are discussed. For now, it is
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sufficient to discuss the less exotic aliases of the floating point
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registers.
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We say aliases because, like the integer registers, how you reference a
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floating point register determines how it is interpreted.
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For example, in the following image, note the overlap of two single
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precision floats within a single double precision floating point
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register.
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It is worth noting early and often that you should not mix dealing
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with different precisions assuming that because of the overlaps in
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space, you'll get a meaningful result.
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The above image does not show the corresponding layout of [half
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precision](./half.md) floating point registers. `H0` sits in the least
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significant bits of `S0` and so on.
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