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Merged
kkysen merged 11 commits into from
Mar 18, 2026
Merged

transpile: fix atomic intrinsics in edition 2024 #1658

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ee3efb6
transpile: call `static_order(order)` earlier, shadowing `order`
kkysen Mar 13, 2026
cbeff24
transpile: hoist `fn order_name` to global scope
kkysen Mar 13, 2026
5f37644
transpile: use `order_name` for the suffix in translating `__sync_*`
kkysen Mar 14, 2026
89dfc1c
transpile: rename `fn order_{name => suffix}` since it's used as the …
kkysen Mar 14, 2026
6b4a1dd
transpile: refactor out `fn atomic_intrinsic_expr`
kkysen Mar 14, 2026
cae364f
transpile: refactor `atomic_*` out of atomic intrinsic base name
kkysen Mar 14, 2026
9521e66
transpile: refactor out `fn atomic_intrinisc_cxchg_expr`
kkysen Mar 14, 2026
fd1a495
transpile: fix atomic instrinsics in edition 2024
kkysen Mar 14, 2026
e6fb791
transpile: use iterators for `fn atomic_intrinsic_expr_edition_2024`
kkysen Mar 18, 2026
08741b5
transpile: check that `fn atomic_intrinsic_expr`'s `orders` are only …
kkysen Mar 18, 2026
e8192bb
transpile: compute `num_ty_params` from `base_name` instead of specif…
kkysen Mar 18, 2026
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205 changes: 128 additions & 77 deletions c2rust-transpile/src/translator/atomics.rs
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Original file line number Diff line number Diff line change
@@ -1,9 +1,101 @@
use crate::format_translation_err;
use itertools::repeat_n;
use std::sync::atomic::Ordering;

use super::*;
use std::sync::atomic::Ordering;

fn order_suffix(order: Ordering) -> &'static str {
use Ordering::*;
match order {
SeqCst => "seqcst",
AcqRel => "acqrel",
Acquire => "acquire",
Release => "release",
Relaxed => "relaxed",
_ => unreachable!(
"new variants added to `{}`",
std::any::type_name::<Ordering>()
),
}
}

fn order_ty_name(order: Ordering) -> &'static str {
use Ordering::*;
match order {
SeqCst => "SeqCst",
AcqRel => "AcqRel",
Acquire => "Acquire",
Release => "Release",
Relaxed => "Relaxed",
_ => unreachable!(
"new variants added to `{}`",
std::any::type_name::<Ordering>()
),
}
}

impl<'c> Translation<'c> {
fn atomic_intrinsic_expr_edition_2021(
&self,
base_name: &str,
orders: &[Ordering],
Comment thread
kkysen marked this conversation as resolved.
) -> Box<Expr> {
let prefix = ["atomic", base_name];
let suffix = orders.iter().map(|&order| order_suffix(order));
let intrinsic_name = prefix.iter().copied().chain(suffix).join("_");
mk().abs_path_expr(vec!["core", "intrinsics", &intrinsic_name])
}

fn atomic_intrinsic_expr_edition_2024(
&self,
base_name: &str,
orders: &[Ordering],
) -> Box<Expr> {
let num_ty_params = match base_name {
"fence" => 0,
"load" | "store" | "xchg" | "cxchg" | "cxchgweak" => 1,
"xadd" | "xsub" | "or" | "xor" | "nand" | "and" => 2,
_ => unimplemented!("unknown atomic intrinsic: {base_name}"),
};

let args = repeat_n("_".to_owned(), num_ty_params)
.chain(orders.iter().map(|&order| {
let order = order_ty_name(order);
format!("{{ ::core::intrinsics::AtomicOrdering::{order} }}")
}))
.join(", ");
let path = format!("::core::intrinsics::atomic_{base_name}::<{args}>");
// `mk()`/`Builder` doesn't seem to support const generic expressions,
// so re-parsing with `syn` is simpler.
let expr = syn::parse_str::<Expr>(&path)
.unwrap_or_else(|_| panic!("failed to parse intrinsic path: {path}"));
Box::new(expr)
}

pub fn atomic_intrinsic_expr(&self, base_name: &str, orders: &[Ordering]) -> Box<Expr> {
assert!(matches!(
orders,
&[_ /* order */] | &[_ /* order_succ */, _ /* order_fail */]
));

self.use_feature("core_intrinsics");
if self.tcfg.edition < Edition2024 {
self.atomic_intrinsic_expr_edition_2021(base_name, orders)
} else {
self.atomic_intrinsic_expr_edition_2024(base_name, orders)
}
}

fn atomic_intrinsic_cxchg_expr(
&self,
weak: bool,
order_succ: Ordering,
order_fail: Ordering,
) -> Box<Expr> {
let base = if weak { "cxchgweak" } else { "cxchg" };
self.atomic_intrinsic_expr(base, &[order_succ, order_fail])
}

fn convert_constant_bool(&self, expr: CExprId) -> Option<bool> {
let val = self.ast_context.unwrap_cast_expr(expr);
match self.ast_context.index(val).kind {
Expand Down Expand Up @@ -70,28 +162,11 @@ impl<'c> Translation<'c> {
})
}

fn order_name(order: Ordering) -> &'static str {
use Ordering::*;
match order {
SeqCst => "seqcst",
AcqRel => "acqrel",
Acquire => "acquire",
Release => "release",
Relaxed => "relaxed",
_ => unreachable!(
"new variants added to `{}`",
std::any::type_name::<Ordering>()
),
}
}

match name {
"__atomic_load" | "__atomic_load_n" | "__c11_atomic_load" => ptr.and_then(|ptr| {
let intrinsic_name = format!("atomic_load_{}", order_name(static_order(order)));
let order = static_order(order);

self.use_feature("core_intrinsics");

let atomic_load = mk().abs_path_expr(vec!["core", "intrinsics", &intrinsic_name]);
let atomic_load = self.atomic_intrinsic_expr("load", &[order]);
let call = mk().call_expr(atomic_load, vec![ptr]);
if name == "__atomic_load" {
let ret = val1.expect("__atomic_load should have a ret argument");
Expand All @@ -116,16 +191,11 @@ impl<'c> Translation<'c> {
}),

"__atomic_store" | "__atomic_store_n" | "__c11_atomic_store" => {
let order = static_order(order);
let val = val1.expect("__atomic_store must have a val argument");
ptr.and_then(|ptr| {
val.and_then(|val| {
let intrinsic_name =
format!("atomic_store_{}", order_name(static_order(order)));

self.use_feature("core_intrinsics");

let atomic_store =
mk().abs_path_expr(vec!["core", "intrinsics", &intrinsic_name]);
let atomic_store = self.atomic_intrinsic_expr("store", &[order]);
let val = if name == "__atomic_store" {
mk().unary_expr(UnOp::Deref(Default::default()), val)
} else {
Expand Down Expand Up @@ -160,16 +230,11 @@ impl<'c> Translation<'c> {
}

"__atomic_exchange" | "__atomic_exchange_n" | "__c11_atomic_exchange" => {
let order = static_order(order);
let val = val1.expect("__atomic_store must have a val argument");
ptr.and_then(|ptr| {
val.and_then(|val| {
let intrinsic_name =
format!("atomic_xchg_{}", order_name(static_order(order)));

self.use_feature("core_intrinsics");

let fn_path =
mk().abs_path_expr(vec!["core", "intrinsics", &intrinsic_name]);
let fn_path = self.atomic_intrinsic_expr("xchg", &[order]);
let val = if name == "__atomic_exchange" {
mk().unary_expr(UnOp::Deref(Default::default()), val)
} else {
Expand Down Expand Up @@ -218,14 +283,15 @@ impl<'c> Translation<'c> {
_ => weak,
};

let order = static_order(order);
let order_fail = static_order(order_fail);
let weak = static_order(weak);

ptr.and_then(|ptr| {
expected.and_then(|expected| {
desired.and_then(|desired| {
let weak = static_order(weak);
let order = static_order(order);
let order_fail = static_order(order_fail);
use Ordering::*;
let intrinsic_name = match (order, order_fail) {
let (order, order_fail) = match (order, order_fail) {
(_, Release | AcqRel) => None,
(SeqCst, SeqCst | Acquire | Relaxed)
| (AcqRel, Acquire | Relaxed)
Expand All @@ -237,12 +303,6 @@ impl<'c> Translation<'c> {

(_, _) => unreachable!("Did we not handle a case above??"),
}
.map(|(order, order_fail)| {
let weak = if weak { "weak" } else { "" };
let order = order_name(order);
let order_fail = order_name(order_fail);
format!("atomic_cxchg{weak}_{order}_{order_fail}")
})
.ok_or_else(|| {
format_translation_err!(
self.ast_context
Expand All @@ -251,7 +311,6 @@ impl<'c> Translation<'c> {
)
})?;

self.use_feature("core_intrinsics");
let expected =
mk().unary_expr(UnOp::Deref(Default::default()), expected);
let desired = match name {
Expand All @@ -262,7 +321,7 @@ impl<'c> Translation<'c> {
};

let atomic_cxchg =
mk().abs_path_expr(vec!["core", "intrinsics", &intrinsic_name]);
self.atomic_intrinsic_cxchg_expr(weak, order, order_fail);
let call =
mk().call_expr(atomic_cxchg, vec![ptr, expected.clone(), desired]);
let res_name = self.renamer.borrow_mut().fresh();
Expand Down Expand Up @@ -305,28 +364,27 @@ impl<'c> Translation<'c> {
| "__c11_atomic_fetch_or"
| "__c11_atomic_fetch_nand" => {
let intrinsic_name = if name.contains("_add") {
"atomic_xadd"
"xadd"
} else if name.contains("_sub") {
"atomic_xsub"
"xsub"
} else if name.contains("_or") {
"atomic_or"
"or"
} else if name.contains("_xor") {
"atomic_xor"
"xor"
} else if name.contains("_nand") {
"atomic_nand"
"nand"
} else {
"atomic_and"
"and"
};

let intrinsic_suffix = order_name(static_order(order));
let intrinsic_name = format!("{intrinsic_name}_{intrinsic_suffix}");
let order = static_order(order);

let fetch_first =
name.starts_with("__atomic_fetch") || name.starts_with("__c11_atomic_fetch");
let val = val1.expect("__atomic arithmetic operations must have a val argument");
ptr.and_then(|ptr| {
val.and_then(|val| {
self.convert_atomic_op(ctx, &intrinsic_name, ptr, val, fetch_first)
self.convert_atomic_op(ctx, intrinsic_name, order, ptr, val, fetch_first)
})
})
}
Expand All @@ -338,16 +396,16 @@ impl<'c> Translation<'c> {
pub(crate) fn convert_atomic_cxchg(
&self,
ctx: ExprContext,
intrinsic_name: &str,
weak: bool,
order_succ: Ordering,
order_fail: Ordering,
dst: Box<Expr>,
old_val: Box<Expr>,
src_val: Box<Expr>,
returns_val: bool,
) -> TranslationResult<WithStmts<Box<Expr>>> {
self.use_feature("core_intrinsics");

// Emit `atomic_cxchg(a0, a1, a2).idx`
Comment thread
kkysen marked this conversation as resolved.
let atomic_cxchg = mk().abs_path_expr(vec!["core", "intrinsics", intrinsic_name]);
let atomic_cxchg = self.atomic_intrinsic_cxchg_expr(weak, order_succ, order_fail);
let call = mk().call_expr(atomic_cxchg, vec![dst, old_val, src_val]);
let field_idx = if returns_val { 0 } else { 1 };
let call_expr = mk().anon_field_expr(call, field_idx);
Expand All @@ -361,15 +419,14 @@ impl<'c> Translation<'c> {
pub(crate) fn convert_atomic_op(
&self,
ctx: ExprContext,
func_name: &str,
base_name: &str,
order: Ordering,
dst: Box<Expr>,
src: Box<Expr>,
fetch_first: bool,
) -> TranslationResult<WithStmts<Box<Expr>>> {
self.use_feature("core_intrinsics");

// Emit `atomic_func(a0, a1) (op a1)?`
let atomic_func = mk().abs_path_expr(vec!["core", "intrinsics", func_name]);
let atomic_func = self.atomic_intrinsic_expr(base_name, &[order]);

if fetch_first {
let call_expr = mk().call_expr(atomic_func, vec![dst, src]);
Expand All @@ -379,20 +436,14 @@ impl<'c> Translation<'c> {
"Builtin is not supposed to be used",
)
} else {
let (binary_op, is_nand) = if func_name.starts_with("atomic_xadd") {
(BinOp::Add(Default::default()), false)
} else if func_name.starts_with("atomic_xsub") {
(BinOp::Sub(Default::default()), false)
} else if func_name.starts_with("atomic_or") {
(BinOp::BitOr(Default::default()), false)
} else if func_name.starts_with("atomic_xor") {
(BinOp::BitXor(Default::default()), false)
} else if func_name.starts_with("atomic_nand") {
(BinOp::BitAnd(Default::default()), true)
} else if func_name.starts_with("atomic_and") {
(BinOp::BitAnd(Default::default()), false)
} else {
panic!("Unexpected atomic intrinsic name: {}", func_name)
let (binary_op, is_nand) = match base_name {
"xadd" => (BinOp::Add(Default::default()), false),
"xsub" => (BinOp::Sub(Default::default()), false),
"or" => (BinOp::BitOr(Default::default()), false),
"xor" => (BinOp::BitXor(Default::default()), false),
"nand" => (BinOp::BitAnd(Default::default()), true),
"and" => (BinOp::BitAnd(Default::default()), false),
_ => panic!("Unexpected atomic intrinsic base name: {base_name}"),
};

// Since the value of `arg1` is used twice, we need to copy
Expand Down
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