Inline assembly: Clarify references to quoted regs #1191
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
For `lateout` and similar operand direction specifiers, a quoted argument must be an explicit register name, per the EBNF grammar we give. As such, we should not use quotes when describing syntax used with register classes. Further, correct the EBNF: in EBNF, quoted strings are always terminals, but `"<explicit register>"` is intended to be a nonterminal surrounded by literal (terminal) quotation marks. Moving the quotes to their own terminal symbols does require escaping, but makes the terminal/nonterminal distinction clearer. The only other place double-quotes are present in the grammar is inside `STRING_LITERAL`/`RAW_STRING_LITERAL`, so calling attention to this case is worthwhile for clarity.
|
This looks good to me. @Amanieu do you perhaps have any comments? |
Amanieu
reviewed
May 20, 2022
| @@ -184,7 +184,7 @@ Here is the list of currently supported register classes: | |||
| > | |||
| > - On x86-64 the high byte registers (e.g. `ah`) are not available in the `reg_byte` register class. | |||
| > | |||
| > - Some register classes are marked as "Only clobbers" which means that they cannot be used for inputs or outputs, only clobbers of the form `out("reg") _` or `lateout("reg") _`. | |||
There was a problem hiding this comment.
This change is incorrect: clobber-only registers can only be used with explicit registers, not register classes.
There was a problem hiding this comment.
I was misled by the usage of 'reg' here, because 'reg' itself is the name of a register class, so I took this to be naming one register class in a place where any register class was valid. If this is an explicit register name, we should say:
`out(<explicit register>) _` or `lateout(<explicit register>) _`, (for example, `lateout("rax") _`).There was a problem hiding this comment.
Committed a change that hopefully clarifies this.
fw-immunant
commented
May 20, 2022
Amanieu
approved these changes
May 20, 2022
GuillaumeGomez
added a commit
to GuillaumeGomez/rust
that referenced
this pull request
May 25, 2022
Update books ## reference 6 commits in 8e36971959ff238b5aa2575fbc7a2e09e1313e82..b74825d8f88b685e239ade00f00de68ba4cd63d4 2022-05-09 17:20:59 -0700 to 2022-05-20 14:30:30 -0700 - Inline assembly: Clarify references to quoted regs (rust-lang/reference#1191) - Add tile registers to inline-assembly documentation (rust-lang/reference#1220) - Upper bound on hashes in raw string literals (rust-lang/reference#1180) - Remove footnote on warning about lifetime shadowing labels. - Makes explanation for Spans in "Procedural Macros" clearer (rust-lang/reference#1219) - Update "Match Expressions" to remove 'cold' (rust-lang/reference#1216) ## book 18 commits in d9415b7cbfcb4b24062683f429bd0ff535396362..b4dd5f00b87190ad5ef42cbc2a88a783c6ae57ef 2022-05-09 09:10:44 -0400 to 2022-05-24 21:37:06 -0400 - Snapshot of appendices for nostarch - Update rust-analyzer URLs and make links less repetitive - Correct byte string literal type. Fixes rust-lang/book#2631. - Fix verb agreement. Fixes rust-lang/book#3176 - Propagate ch19 edits to src - Edits to chapter 19 from nostarch - Propagate ch18 edits to src - Edits to ch18 from nostarch - Propagate tech review edits to src ch5 - Responses to chapter 5 tech review - Ch5 after tech review - Merge branch 'ch7-edits' - fix: mdBook authors - Propagating ch17 edits to src - Edits from nostarch for ch17 - Fix rust-lang/book#3152 - Wrong character used - & is not valid inside image alt text - Merge branch 'ch20' ## rust-by-example 2 commits in e9f93cfcf410bc092c9107b8a41a82f144c761f2..2ed26865e8c29ef939dc913a97bd321cadd72a9a 2022-05-08 18:24:06 -0300 to 2022-05-18 17:23:47 -0300 - Rework cpuid asm example. (rust-lang/rust-by-example#1542) - chore: better description for eprint macro (rust-lang/rust-by-example#1541) ## rustc-dev-guide 11 commits in 0c02acd..554c00e 2022-05-10 09:45:31 -0300 to 2022-05-24 17:15:35 -0700 - Cleanup rustdoc-internals - Fix some wording on the "Incremental Compilation In Detail" page - Exclude `tomlee.co` from link-checking (rust-lang/rustc-dev-guide#1356) - Add note about patching dependencies and warnings. (rust-lang/rustc-dev-guide#1354) - make sentence more simple (rust-lang/rustc-dev-guide#1353) - Update some links and docs (rust-lang/rustc-dev-guide#1340) - Replace a broken YouTube link (rust-lang/rustc-dev-guide#1295) - Edit the "Compiler Source Code" chapter (rust-lang/rustc-dev-guide#1307) - Add docs for logging of queries. (rust-lang/rustc-dev-guide#1350) - Fix configuration names for vscode/r-a (rust-lang/rustc-dev-guide#1352) - Update docs for deprecated attribute (rust-lang/rustc-dev-guide#1338)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
For
lateoutand similar operand direction specifiers, a quoted argument must be an explicit register name, per the EBNF grammar we give. As such, we should not use quotes when describing syntax used with register classes.Further, correct the EBNF: in EBNF, quoted strings are always terminals, but
"<explicit register>"is intended to be a nonterminal surrounded by literal (terminal) quotation marks. Moving the quotes to their own terminal symbols does require escaping, but makes the terminal/nonterminal distinction clearer. The only other place double-quotes are present in the grammar is insideSTRING_LITERAL/RAW_STRING_LITERAL, so calling attention to this case is worthwhile for clarity.