asm: Allow multiple template string arguments; interpret them as newline-separated by joshtriplett · Pull Request #73364 · rust-lang/rust

joshtriplett · 2020-06-15T07:03:17Z

Allow the asm! macro to accept a series of template arguments, and interpret them as if they were concatenated with a '\n' between them. This allows writing an asm! where each line of assembly appears in a separate template string argument.

This syntax makes it possible for rustfmt to reliably format and indent each line of assembly, without risking changes to the inside of a template string. It also avoids the complexity of having the user carefully format and indent a multi-line string (including where to put the surrounding quotes), and avoids the extra indentation and lines of a call to concat!.

For example, rewriting the second example from the blog post on the new inline assembly syntax using multiple template strings:

fnmain(){letmut bits = [0u8;64];for value in0..=1024u64{let popcnt;unsafe{asm!(" popcnt {popcnt}, {v}","2:"," blsi rax, {v}"," jz 1f"," xor {v}, rax"," tzcnt rax, rax"," stosb"," jmp 2b","1:",
v = inout(reg) value => _,
popcnt = out(reg) popcnt,
out("rax") _,// scratch
inout("rdi") bits.as_mut_ptr() => _,);}println!("bits of {}: {:?}", value,&bits[0..popcnt]);}}

Note that all the template strings must appear before all other arguments; you cannot, for instance, provide a series of template strings intermixed with the corresponding operands.

…xpect` Currently, `asm!` parsing uses an `expect` for the last parsed pseudo-keyword (`sym`), which makes it difficult to extend without simultaneously refactoring. Use `eat` for the last pseudo-keyword, and then add an `else` that fails parsing. No change to error output.

pprust uses `print_string` to write out the template string, and `print_string` already calls `escape_debug`, so `impl fmt::Display for InlineAsmTemplatePiece` shouldn't do an additional `escape_debug`. This fixes a pretty-printing bug that translated `asm!("...\n...")` to `asm!("...\\n...")`

rust-highfive · 2020-06-15T07:03:20Z

r? @eddyb

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joshtriplett · 2020-06-15T07:03:42Z

r? @Amanieu

Amanieu

Have you checked that this is correctly handling implicitly number arguments in the template over multiple template strings? For example asm!("{}", "{}", in(reg) a, in(reg) b).

…ated Allow the `asm!` macro to accept a series of template arguments, and interpret them as if they were concatenated with a '\n' between them. This allows writing an `asm!` where each line of assembly appears in a separate template string argument. This syntax makes it possible for rustfmt to reliably format and indent each line of assembly, without risking changes to the inside of a template string. It also avoids the complexity of having the user carefully format and indent a multi-line string (including where to put the surrounding quotes), and avoids the extra indentation and lines of a call to `concat!`. For example, rewriting the second example from the [blog post on the new inline assembly syntax](https://blog.rust-lang.org/inside-rust/2020/06/08/new-inline-asm.html) using multiple template strings: ```rust fn main() { let mut bits = [0u8; 64]; for value in 0..=1024u64 { let popcnt; unsafe { asm!( " popcnt {popcnt}, {v}", "2:", " blsi rax, {v}", " jz 1f", " xor {v}, rax", " tzcnt rax, rax", " stosb", " jmp 2b", "1:", v = inout(reg) value => _, popcnt = out(reg) popcnt, out("rax") _, // scratch inout("rdi") bits.as_mut_ptr() => _, ); } println!("bits of {}: {:?}", value, &bits[0..popcnt]); } } ``` Note that all the template strings must appear before all other arguments; you cannot, for instance, provide a series of template strings intermixed with the corresponding operands. In order to get srcloc mappings right for macros that generate multi-line string literals, create one line_span for each line in the string literal, each pointing to the macro. Make `rustc_parse_format::Parser::curarg` `pub`, so that we can propagate it from one template string argument to the next.

petrochenkov · 2020-06-15T20:29:00Z

and interpret them as if they were concatenated with a '\n' between them

So it's not just C-style concatenation of neighboring string literals for people accustomed to it.
This certainly makes it more useful.

…uments Update all examples to use the new formatting, and update explanations to document it.

joshtriplett · 2020-06-15T20:32:28Z

@Amanieu

Can you update src/doc/unstable-book/src/library-features/asm.md with the same changes you made to the RFC?

Done; thanks!

Amanieu · 2020-06-16T09:31:43Z

@bors r+

bors · 2020-06-16T09:31:44Z

📌 Commit fd9ed30 has been approved by Amanieu

@ghost

…arth Rollup of 13 pull requests Successful merges: - rust-lang#71568 (Document unsafety in slice/sort.rs) - rust-lang#72709 (`#[deny(unsafe_op_in_unsafe_fn)]` in liballoc) - rust-lang#73214 (Add asm!() support for hexagon) - rust-lang#73248 (save_analysis: improve handling of enum struct variant) - rust-lang#73257 (ty: projections in `transparent_newtype_field`) - rust-lang#73261 (Suggest `?Sized` when applicable for ADTs) - rust-lang#73300 (Implement crate-level-only lints checking.) - rust-lang#73334 (Note numeric literals that can never fit in an expected type) - rust-lang#73357 (Use `LocalDefId` for import IDs in trait map) - rust-lang#73364 (asm: Allow multiple template string arguments; interpret them as newline-separated) - rust-lang#73382 (Only display other method receiver candidates if they actually apply) - rust-lang#73465 (Add specialization of `ToString for char`) - rust-lang#73489 (Refactor hir::Place) Failed merges: r? @ghost

rust-lang/rust#73364 implemented support for providing multiple lines of assembly as separate arguments to `asm!`; update the blog post to use that new syntax, so that people who find it will use that style as an example.

* inline-asm: Update for new style rust-lang/rust#73364 implemented support for providing multiple lines of assembly as separate arguments to `asm!`; update the blog post to use that new syntax, so that people who find it will use that style as an example. * inline-asm: Outdent * inline asm: Update play link

joshtriplett added 2 commits June 14, 2020 14:17

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joshtriplett force-pushed the inline-asm branch from c41911b to 62f9ffaCompare June 15, 2020 09:49

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Formatting guidelines for inline assembly rust-lang/style-team#152
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inline-asm rust-lang/lang-team#20
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asm: Update chapter in unstable book for multiple template string arg…
fd9ed30
…uments Update all examples to use the new formatting, and update explanations to document it.

joshtriplett force-pushed the inline-asm branch from 8f168da to fd9ed30Compare June 15, 2020 20:31

joshtriplett changed the title ~~asm: Allow multiple template strings; interpret them as newline-separated~~asm: Allow multiple template string arguments; interpret them as newline-separatedJun 15, 2020

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 16, 2020

Amanieu mentioned this pull request Jun 16, 2020
Allow multiple asm! options groups and report an error on duplicate options #73227
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Manishearth mentioned this pull request Jun 19, 2020
Rollup of 13 pull requests #73511
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bors merged commit 687f929 into rust-lang:masterJun 20, 2020

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inline-asm: Update for new style rust-lang/blog.rust-lang.org#623
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cuviper added this to the 1.46 milestone May 2, 2024

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