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rustc_codegen_llvm: use threadlocal.address intrinsic to access TLS #139385

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Merged
merged 1 commit into from
May 30, 2025
Merged

rustc_codegen_llvm: use threadlocal.address intrinsic to access TLS #139385

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12 changes: 9 additions & 3 deletions compiler/rustc_codegen_llvm/src/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1454,9 +1454,15 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
impl<'ll> StaticBuilderMethods for Builder<'_, 'll, '_> {
fn get_static(&mut self, def_id: DefId) -> &'ll Value {
// Forward to the `get_static` method of `CodegenCx`
let s = self.cx().get_static(def_id);
// Cast to default address space if globals are in a different addrspace
self.cx().const_pointercast(s, self.type_ptr())
let global = self.cx().get_static(def_id);
if self.cx().tcx.is_thread_local_static(def_id) {
let pointer = self.call_intrinsic("llvm.threadlocal.address", &[global]);
// Cast to default address space if globals are in a different addrspace
self.pointercast(pointer, self.type_ptr())
} else {
// Cast to default address space if globals are in a different addrspace
self.cx().const_pointercast(global, self.type_ptr())
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It would have been fine to use pointercast for both cases, but this is ok as well.

}
}
}

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1 change: 1 addition & 0 deletions compiler/rustc_codegen_llvm/src/context.rs
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Expand Up @@ -1198,6 +1198,7 @@ impl<'ll> CodegenCx<'ll, '_> {
}

ifn!("llvm.ptrmask", fn(ptr, t_isize) -> ptr);
ifn!("llvm.threadlocal.address", fn(ptr) -> ptr);

None
}
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16 changes: 10 additions & 6 deletions tests/codegen/thread-local.rs
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Expand Up @@ -14,37 +14,41 @@ use std::cell::Cell;

thread_local!(static A: Cell<u32> = const { Cell::new(1) });

// CHECK: [[TLS_AUX:@.+]] = external thread_local local_unnamed_addr global i64
// CHECK: [[TLS:@.+]] = internal thread_local unnamed_addr global
// CHECK: [[TLS_AUX:@.+]] = external thread_local{{.*}} global i64
// CHECK: [[TLS:@.+]] = internal thread_local{{.*}} global

// CHECK-LABEL: @get
#[no_mangle]
fn get() -> u32 {
// CHECK: [[RET_0:%.+]] = load i32, {{.*}}[[TLS]]{{.*}}
// CHECK: [[PTR:%.+]] = tail call {{.*}} ptr @llvm.threadlocal.address.p0(ptr [[TLS]])
// CHECK-NEXT: [[RET_0:%.+]] = load i32, ptr [[PTR]]
// CHECK-NEXT: ret i32 [[RET_0]]
A.with(|a| a.get())
}

// CHECK-LABEL: @set
#[no_mangle]
fn set(v: u32) {
// CHECK: store i32 %0, {{.*}}[[TLS]]{{.*}}
// CHECK: [[PTR:%.+]] = tail call {{.*}} ptr @llvm.threadlocal.address.p0(ptr [[TLS]])
// CHECK-NEXT: store i32 %0, ptr [[PTR]]
// CHECK-NEXT: ret void
A.with(|a| a.set(v))
}

// CHECK-LABEL: @get_aux
#[no_mangle]
fn get_aux() -> u64 {
// CHECK: [[RET_1:%.+]] = load i64, {{.*}}[[TLS_AUX]]
// CHECK: [[PTR:%.+]] = tail call {{.*}} ptr @llvm.threadlocal.address.p0(ptr [[TLS_AUX]])
// CHECK-NEXT: [[RET_1:%.+]] = load i64, ptr [[PTR]]
// CHECK-NEXT: ret i64 [[RET_1]]
aux::A.with(|a| a.get())
}

// CHECK-LABEL: @set_aux
#[no_mangle]
fn set_aux(v: u64) {
// CHECK: store i64 %0, {{.*}}[[TLS_AUX]]
// CHECK: [[PTR:%.+]] = tail call {{.*}} ptr @llvm.threadlocal.address.p0(ptr [[TLS_AUX]])
// CHECK-NEXT: store i64 %0, ptr [[PTR]]
// CHECK-NEXT: ret void
aux::A.with(|a| a.set(v))
}
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