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.
Fix #[thread_local] statics as asm! sym operands
The `asm!` RFC specifies that `#[thread_local]` statics may be used as `sym` operands for inline assembly.
This also fixes a regression in the handling of `#[thread_local]` during monomorphization which caused link-time errors with multiple codegen units, most likely introduced by #71192.
r? @oli-obk
Suggest including unused asm arguments in a comment to avoid error
We require all arguments to an `asm!` to be used in the template string, just like format strings. However in some cases (e.g. `black_box`) it may be desirable to have `asm!` arguments that are not used in the template string.
Currently this is a hard error rather than a lint since `#[allow]` does not work on macros (#63221), so this PR suggests using the unused arguments in an asm comment as a workaround.
r? @petrochenkov
Improve inline asm error diagnostics
Previously we were just using the raw LLVM error output (with line, caret, etc) as the diagnostic message, which ends up looking rather out of place with our existing diagnostics.
The new diagnostics properly format the diagnostics and also take advantage of LLVM's per-line `srcloc` attribute to map an error in inline assembly directly to the relevant line of source code.
Incidentally also fixes#71639 by disabling `srcloc` metadata during LTO builds since we don't know what crate it might have come from. We can only resolve `srcloc`s from the currently crate since it indexes into the source map for the current crate.
Fixes#72664Fixes#71639
r? @petrochenkov
### Old style
```rust
#![feature(llvm_asm)]
fn main() {
unsafe {
let _x: i32;
llvm_asm!(
"mov $0, $1
invalid_instruction $0, $1
mov $0, $1"
: "=&r" (_x)
: "r" (0)
:: "intel"
);
}
}
```
```
error: <inline asm>:3:14: error: invalid instruction mnemonic 'invalid_instruction'
invalid_instruction ecx, eax
^~~~~~~~~~~~~~~~~~~
--> src/main.rs:6:9
|
6 | / llvm_asm!(
7 | | "mov $0, $1
8 | | invalid_instruction $0, $1
9 | | mov $0, $1"
... |
12 | | :: "intel"
13 | | );
| |__________^
```
### New style
```rust
#![feature(asm)]
fn main() {
unsafe {
asm!(
"mov {0}, {1}
invalid_instruction {0}, {1}
mov {0}, {1}",
out(reg) _,
in(reg) 0i64,
);
}
}
```
```
error: invalid instruction mnemonic 'invalid_instruction'
--> test.rs:7:14
|
7 | invalid_instruction {0}, {1}
| ^
|
note: instantiated into assembly here
--> <inline asm>:3:14
|
3 | invalid_instruction rax, rcx
| ^^^^^^^^^^^^^^^^^^^
```
This commit completely removes usage of the `panictry!` macro from
outside libsyntax. The macro causes parse errors to be fatal, so using
it in libsyntax_ext caused parse failures *within* a syntax extension to
be fatal, which is probably not intended.
Furthermore, this commit adds spans to diagnostics emitted by empty
extensions if they were missing, à la #56491.
I also added `// skip-codegen` to each one, to address potential concerns
that this change would otherwise slow down our test suite spending time
generating code for files that are really just meant to be checks of
compiler diagnostics.
(However, I will say: My preference is to not use `// skip-codegen` if
one can avoid it. We can use all the testing of how we drive LLVM that
we can get...)
(Updated post rebase.)
