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Re-implement atomic load and stores

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The AArch64 support was a bit broken and was using Armv7 style
barriers, which aren't required with Armv8 acquire-release
load/stores.

The fallback CAS loops and RMW, for AArch64, have also been updated
to use acquire-release, exclusive, instructions which, again, remove
the need for barriers. The CAS loop has also been further optimised
by using the extending form of the cmp instruction.

Copyright (c) 2021, Arm Limited.
This commit is contained in:
Sam Parker
2021-07-29 15:41:45 +01:00
parent 85f16f488d
commit cbb7229457
12 changed files with 564 additions and 220 deletions
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52
cranelift/codegen/src/isa/aarch64/lower_inst.rs
View File

@@ -1522,28 +1522,40 @@ pub(crate) fn lower_insn_to_regs<C: LowerCtx<I = Inst>>(
}
}
Opcode::AtomicLoad => {
let r_data = get_output_reg(ctx, outputs[0]).only_reg().unwrap();
let r_addr = put_input_in_reg(ctx, inputs[0], NarrowValueMode::None);
let ty_access = ty.unwrap();
assert!(is_valid_atomic_transaction_ty(ty_access));
ctx.emit(Inst::AtomicLoad {
ty: ty_access,
r_data,
r_addr,
});
Opcode::AtomicLoad
| Opcode::AtomicUload8
| Opcode::AtomicUload16
| Opcode::AtomicUload32 => {
let rt = get_output_reg(ctx, outputs[0]).only_reg().unwrap();
let rn = put_input_in_reg(ctx, inputs[0], NarrowValueMode::None);
let ty = ty.unwrap();
let access_ty = match op {
Opcode::AtomicLoad => ty,
Opcode::AtomicUload8 => I8,
Opcode::AtomicUload16 => I16,
Opcode::AtomicUload32 => I32,
_ => panic!(),
};
assert!(is_valid_atomic_transaction_ty(access_ty));
ctx.emit(Inst::LoadAcquire { access_ty, rt, rn });
}
Opcode::AtomicStore => {
let r_data = put_input_in_reg(ctx, inputs[0], NarrowValueMode::None);
let r_addr = put_input_in_reg(ctx, inputs[1], NarrowValueMode::None);
let ty_access = ctx.input_ty(insn, 0);
assert!(is_valid_atomic_transaction_ty(ty_access));
ctx.emit(Inst::AtomicStore {
ty: ty_access,
r_data,
r_addr,
});
Opcode::AtomicStore
| Opcode::AtomicStore32
| Opcode::AtomicStore16
| Opcode::AtomicStore8 => {
let rt = put_input_in_reg(ctx, inputs[0], NarrowValueMode::None);
let rn = put_input_in_reg(ctx, inputs[1], NarrowValueMode::None);
let ty = ctx.input_ty(insn, 0);
let access_ty = match op {
Opcode::AtomicStore => ty,
Opcode::AtomicStore32 => I32,
Opcode::AtomicStore16 => I16,
Opcode::AtomicStore8 => I8,
_ => unreachable!(),
};
assert!(is_valid_atomic_transaction_ty(access_ty));
ctx.emit(Inst::StoreRelease { access_ty, rt, rn });
}
Opcode::Fence => {