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Disambiguate the use of the term "reserved" for HINT instructions #990

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@asb asb commented Mar 14, 2023

As was raised in #300, the overloaded use of the term "reserved" when listing HINT encodings is potentially confusing. As clarified in that thread, these encodings are "reserved" in the intuitive English language meaning of the word, but are not part of the "reserved instruction-set category" as defined in the section 1.3 introduction and further elaborated in section 2.2 "Base Instruction Formats" (which notes how platforms can choose to raise an illegal-instruction exception for reserved instruction encodings).

As was raised in riscv#300, the overloaded use of the term "reserved" when
listing HINT encodings is potentially confusing. As clarified in that
thread, these encodings are "reserved" in the intuitive English language
meaning of the word, but are _not_ part of the "reserved instruction-set
category" as defined in the section 1.3 introduction and further
elaborated in section 2.2 "Base Instruction Formats" (which notes how
platforms can choose to raise an illegal-instruction exception for
reserved instruction encodings).
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asb commented Mar 29, 2023

Friendly ping on this as it's been a couple of weeks.

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Maybe we should just avoid use of the word "reserved" in this paragraph and in the tables, and instead use the word "designated". What do you think @asb @kasanovic?

asb added a commit to asb/riscv-isa-manual that referenced this pull request Mar 29, 2023
The term "reserved" could be ambiguous, as it might be understood to
refer to the "reserved instruction-set category" as defined in the
section 1.3 instruction and further elaborated in section 2.2 "Base
Instruction Formats". Avoid this potential confusion by using
"designated" instead, which also matches the terminology used for HINT
encodings intended for custom use.

This is an alternative to riscv#990.
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asb commented Mar 29, 2023

That's a good idea, especially as we already say "Designated for custom use" already. I've submitted #1001 as an alternative PR using that approach.

aswaterman pushed a commit that referenced this pull request Mar 29, 2023
…#1001)

The term "reserved" could be ambiguous, as it might be understood to
refer to the "reserved instruction-set category" as defined in the
section 1.3 instruction and further elaborated in section 2.2 "Base
Instruction Formats". Avoid this potential confusion by using
"designated" instead, which also matches the terminology used for HINT
encodings intended for custom use.

This is an alternative to #990.
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Superseded by #1001

@aswaterman aswaterman closed this Mar 29, 2023
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2 participants