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Use a C-safe return type for __rust_[ui]128_* overflowing intrinsics
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Combined with [1], this will change the overflowing multiplication
operations to return an `extern "C"`-safe type.

Link: rust-lang/compiler-builtins#735 [1]
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@tgross35
tgross35 committed Jan 15, 2025
1 parent f8b89a3 commit 0f89f3f
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Showing 2 changed files with 64 additions and 65 deletions.
123 changes: 60 additions & 63 deletions src/int.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -322,36 +322,26 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
},
}
} else {
match new_kind {
Int(I128) | Uint(U128) => {
let func_name = match oop {
OverflowOp::Add => match new_kind {
Int(I128) => "__rust_i128_addo",
Uint(U128) => "__rust_u128_addo",
_ => unreachable!(),
},
OverflowOp::Sub => match new_kind {
Int(I128) => "__rust_i128_subo",
Uint(U128) => "__rust_u128_subo",
_ => unreachable!(),
},
OverflowOp::Mul => match new_kind {
Int(I128) => "__rust_i128_mulo", // TODO(antoyo): use __muloti4d instead?
Uint(U128) => "__rust_u128_mulo",
_ => unreachable!(),
},
};
return self.operation_with_overflow(func_name, lhs, rhs);
}
_ => match oop {
OverflowOp::Mul => match new_kind {
Int(I32) => "__mulosi4",
Int(I64) => "__mulodi4",
_ => unreachable!(),
},
_ => unimplemented!("overflow operation for {:?}", new_kind),
let (func_name, width) = match oop {
OverflowOp::Add => match new_kind {
Int(I128) => ("__rust_i128_addo", 128),
Uint(U128) => ("__rust_u128_addo", 128),
_ => unreachable!(),
},
}
OverflowOp::Sub => match new_kind {
Int(I128) => ("__rust_i128_subo", 128),
Uint(U128) => ("__rust_u128_subo", 128),
_ => unreachable!(),
},
OverflowOp::Mul => match new_kind {
Int(I32) => ("__mulosi4", 32),
Int(I64) => ("__mulodi4", 64),
Int(I128) => ("__rust_i128_mulo", 128), // TODO(antoyo): use __muloti4d instead?
Uint(U128) => ("__rust_u128_mulo", 128),
_ => unreachable!(),
},
};
return self.operation_with_overflow(func_name, lhs, rhs, width);
};

let intrinsic = self.context.get_builtin_function(name);
Expand All @@ -364,80 +354,87 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
(res.dereference(self.location).to_rvalue(), overflow)
}

/// Non-`__builtin_*` overflow operations with a `fn(T, T, &mut i32) -> T` signature.
pub fn operation_with_overflow(
&self,
func_name: &str,
lhs: RValue<'gcc>,
rhs: RValue<'gcc>,
width: u64,
) -> (RValue<'gcc>, RValue<'gcc>) {
let a_type = lhs.get_type();
let b_type = rhs.get_type();
debug_assert!(a_type.dyncast_array().is_some());
debug_assert!(b_type.dyncast_array().is_some());
let overflow_type = self.i32_type;
let overflow_param_type = overflow_type.make_pointer();
let res_type = a_type;

let overflow_value =
self.current_func().new_local(self.location, overflow_type, "overflow");
let overflow_addr = overflow_value.get_address(self.location);

let param_a = self.context.new_parameter(self.location, a_type, "a");
let param_b = self.context.new_parameter(self.location, b_type, "b");
let result_field = self.context.new_field(self.location, a_type, "result");
let overflow_field = self.context.new_field(self.location, self.bool_type, "overflow");

let ret_ty = Ty::new_tup(self.tcx, &[self.tcx.types.i128, self.tcx.types.bool]);
let param_overflow =
self.context.new_parameter(self.location, overflow_param_type, "overflow");

let a_elem_type = a_type.dyncast_array().expect("non-array a value");
debug_assert!(a_elem_type.is_integral());
let res_ty = match width {
32 => self.tcx.types.i32,
64 => self.tcx.types.i64,
128 => self.tcx.types.i128,
_ => unreachable!("unexpected integer size"),
};
let layout = self
.tcx
.layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(ret_ty))
.layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(res_ty))
.unwrap();

let arg_abi = ArgAbi { layout, mode: PassMode::Direct(ArgAttributes::new()) };
let mut fn_abi = FnAbi {
args: vec![arg_abi.clone(), arg_abi.clone()].into_boxed_slice(),
args: vec![arg_abi.clone(), arg_abi.clone(), arg_abi.clone()].into_boxed_slice(),
ret: arg_abi,
c_variadic: false,
fixed_count: 2,
fixed_count: 3,
conv: Conv::C,
can_unwind: false,
};
fn_abi.adjust_for_foreign_abi(self.cx, spec::abi::Abi::C { unwind: false }).unwrap();

let indirect = matches!(fn_abi.ret.mode, PassMode::Indirect { .. });

let return_type = self
.context
.new_struct_type(self.location, "result_overflow", &[result_field, overflow_field]);
let result = if indirect {
let return_value =
self.current_func().new_local(self.location, return_type.as_type(), "return_value");
let return_param_type = return_type.as_type().make_pointer();
let return_param =
self.context.new_parameter(self.location, return_param_type, "return_value");
let ret_indirect = matches!(fn_abi.ret.mode, PassMode::Indirect { .. });

let result = if ret_indirect {
let res_value = self.current_func().new_local(self.location, res_type, "result_value");
let res_addr = res_value.get_address(self.location);
let res_param_type = res_type.make_pointer();
let param_res = self.context.new_parameter(self.location, res_param_type, "result");

let func = self.context.new_function(
self.location,
FunctionType::Extern,
self.type_void(),
&[return_param, param_a, param_b],
&[param_res, param_a, param_b, param_overflow],
func_name,
false,
);
self.llbb().add_eval(
self.location,
self.context.new_call(self.location, func, &[
return_value.get_address(self.location),
lhs,
rhs,
]),
);
return_value.to_rvalue()
let _void =
self.context.new_call(self.location, func, &[res_addr, lhs, rhs, overflow_addr]);
res_value.to_rvalue()
} else {
let func = self.context.new_function(
self.location,
FunctionType::Extern,
return_type.as_type(),
&[param_a, param_b],
res_type,
&[param_a, param_b, param_overflow],
func_name,
false,
);
self.context.new_call(self.location, func, &[lhs, rhs])
self.context.new_call(self.location, func, &[lhs, rhs, overflow_addr])
};
let overflow = result.access_field(self.location, overflow_field);
let int_result = result.access_field(self.location, result_field);
(int_result, overflow)

(result, self.context.new_cast(self.location, overflow_value, self.bool_type).to_rvalue())
}

pub fn gcc_icmp(
Expand Down
6 changes: 4 additions & 2 deletions src/intrinsic/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1001,7 +1001,8 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
128 => "__rust_i128_addo",
_ => unreachable!(),
};
let (int_result, overflow) = self.operation_with_overflow(func_name, lhs, rhs);
let (int_result, overflow) =
self.operation_with_overflow(func_name, lhs, rhs, width);
self.llbb().add_assignment(self.location, res, int_result);
overflow
};
Expand Down Expand Up @@ -1071,7 +1072,8 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
128 => "__rust_i128_subo",
_ => unreachable!(),
};
let (int_result, overflow) = self.operation_with_overflow(func_name, lhs, rhs);
let (int_result, overflow) =
self.operation_with_overflow(func_name, lhs, rhs, width);
self.llbb().add_assignment(self.location, res, int_result);
overflow
};
Expand Down

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