Relax ordering rules for asm! operands
#1323
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This updates the reference to match the changes in rust-lang/rust#105798
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@bors r+ |
| asm := "asm!(" format_string *("," format_string) *("," [ident "="] operand) *("," clobber_abi) *("," options) [","] ")" | ||
| global_asm := "global_asm!(" format_string *("," format_string) *("," [ident "="] operand) *("," options) [","] ")" | ||
| operand := reg_operand / clobber_abi / options | ||
| asm := "asm!(" format_string *("," format_string) *("," operand) [","] ")" |
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This grammar doesn't seem to capture the order requirements for how it is parsed. Am I missing something for how this is defined? That is, why is it not something closer to:
asm := "asm!(" format_string *("," format_string) *("," operand) *("," ident "=" operand) *("," options) [","] ")"
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The new rules allow options and operands to be freely mixed, so there are no order requirements anymore (except that the template strings must come first).
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I think what I'm getting after is to capture the rule that positional operands must come before named operands. This grammar seems to allow:
let x: i64;
asm!("add {}, {foo}, {}", out(reg) x, foo=in(reg) 2, in(reg) 1);But that generates an error "positional arguments cannot follow named arguments or explicit register arguments".
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Right, but then again options and clobber_abi can appear in any position between named & positional arguments. It's a bit difficult to express all the details in the grammar.
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If I understand how it parses correctly, the following doesn't seem too unwieldy:
asm := "asm!(" format_string *("," format_string) operands ")"
operands := *("," reg_operand / clobber_abi / options) *("," ident "=" reg_operand) *("," clobber_abi / options)
Does that seem like it would be OK to have?
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I gave this a try but I think it just makes the grammar harder to read overall. I prefer leaving it as it currently is and describing the operand ordering constraints in the text.
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The example you gave isn't actually correct since it doesn't cover explicit register operands which don't have names and can be mixed with named operands.
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That's fair. Thanks for taking a look!
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@rustbot labels -I-lang-nominated |
Update books ## rust-lang/nomicon 1 commits in 1f3e4cd4fd88b5b5d45feb86a11b6d2f93e5a974..b5f7500fc40775096c2bbd204eae096612cf9047 2023-03-27 13:47:36 UTC to 2023-03-27 13:47:36 UTC - Fix typo in 3.8 Subtyping and Variance (rust-lang/nomicon#395) ## rust-lang/reference 4 commits in 24c87f6663aed55b05d2cc286878f28f21918825..3c47807a3131b3c7cacb508f52632078d253cd0a 2023-03-26 18:42:43 UTC to 2023-03-14 18:28:23 UTC - Relax ordering rules for `asm!` operands (rust-lang/reference#1323) - Improve labeled blocks documentation (rust-lang/reference#1342) - Inline assembly: Fix repeated and unordered items in guaranteed directives (rust-lang/reference#1341) - Clarify that free constants are always evaluated at compile time (rust-lang/reference#1328) ## rust-lang/rust-by-example 7 commits in af0998b7473839ca75563ba3d3e7fd0160bef235..cfbfd648ce33926c3490f24de9a5b56cce404b88 2023-03-21 12:05:17 UTC to 2023-03-21 11:58:20 UTC - Fix two typos in the asm chapter (rust-lang/rust-by-example#1692) - Change `runtime` error to `compile time` error (rust-lang/rust-by-example#1690) - Fix tests running on non-x86 platforms. (rust-lang/rust-by-example#1687) - Remove trailing semicolon from macro expression (rust-lang/rust-by-example#1683) - Explained why it should not work in Chapter 4.1 (rust-lang/rust-by-example#1682) - Fix comment to mention the correct type of error (rust-lang/rust-by-example#1680) - Improve the content for `read_lines` (rust-lang/rust-by-example#1679) ## rust-lang/rustc-dev-guide 9 commits in b1b6d693cd1461e53de4132c1b183ace31cd36e5..d08baa166b463537229eeb737c4ccadabd83cf78 2023-03-26 17:55:53 UTC to 2023-03-14 03:50:20 UTC - Add locale_resources (rust-lang/rustc-dev-guide#1651) - Don't require $GITHUB_TOKEN to build locally (rust-lang/rustc-dev-guide#1652) - bootsrapping stages overview list (rust-lang/rustc-dev-guide#1555) - Update labels overview (rust-lang/rustc-dev-guide#1639) - first mention of type, and add a link (rust-lang/rustc-dev-guide#1643) - Add SIP solution for macOS users (rust-lang/rustc-dev-guide#1636) - Add chapter on fuzzing (rust-lang/rustc-dev-guide#1646) - Fix "Crate disambiguator" in libs-and-metadata.md (rust-lang/rustc-dev-guide#1648) - Update rustdoc-internals.md (rust-lang/rustc-dev-guide#1644)
This updates the reference to match the changes in rust-lang/rust#105798