1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
|
#[cfg(feature="master")]
use gccjit::{FnAttribute, Visibility};
use gccjit::{FunctionType, Function};
use rustc_middle::ty::{self, Instance, TypeVisitableExt};
use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt};
use crate::attributes;
use crate::context::CodegenCx;
/// Codegens a reference to a fn/method item, monomorphizing and
/// inlining as it goes.
///
/// # Parameters
///
/// - `cx`: the crate context
/// - `instance`: the instance to be instantiated
pub fn get_fn<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, instance: Instance<'tcx>) -> Function<'gcc> {
let tcx = cx.tcx();
assert!(!instance.substs.needs_infer());
assert!(!instance.substs.has_escaping_bound_vars());
let sym = tcx.symbol_name(instance).name;
if let Some(&func) = cx.function_instances.borrow().get(&instance) {
return func;
}
let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());
let func =
if let Some(_func) = cx.get_declared_value(&sym) {
// FIXME(antoyo): we never reach this because get_declared_value only returns global variables
// and here we try to get a function.
unreachable!();
/*
// Create a fn pointer with the new signature.
let ptrty = fn_abi.ptr_to_gcc_type(cx);
// This is subtle and surprising, but sometimes we have to bitcast
// the resulting fn pointer. The reason has to do with external
// functions. If you have two crates that both bind the same C
// library, they may not use precisely the same types: for
// example, they will probably each declare their own structs,
// which are distinct types from LLVM's point of view (nominal
// types).
//
// Now, if those two crates are linked into an application, and
// they contain inlined code, you can wind up with a situation
// where both of those functions wind up being loaded into this
// application simultaneously. In that case, the same function
// (from LLVM's point of view) requires two types. But of course
// LLVM won't allow one function to have two types.
//
// What we currently do, therefore, is declare the function with
// one of the two types (whichever happens to come first) and then
// bitcast as needed when the function is referenced to make sure
// it has the type we expect.
//
// This can occur on either a crate-local or crate-external
// reference. It also occurs when testing libcore and in some
// other weird situations. Annoying.
if cx.val_ty(func) != ptrty {
// TODO(antoyo): cast the pointer.
func
}
else {
func
}*/
}
else {
cx.linkage.set(FunctionType::Extern);
let func = cx.declare_fn(&sym, &fn_abi);
attributes::from_fn_attrs(cx, func, instance);
let instance_def_id = instance.def_id();
// TODO(antoyo): set linkage and attributes.
// Apply an appropriate linkage/visibility value to our item that we
// just declared.
//
// This is sort of subtle. Inside our codegen unit we started off
// compilation by predefining all our own `MonoItem` instances. That
// is, everything we're codegenning ourselves is already defined. That
// means that anything we're actually codegenning in this codegen unit
// will have hit the above branch in `get_declared_value`. As a result,
// we're guaranteed here that we're declaring a symbol that won't get
// defined, or in other words we're referencing a value from another
// codegen unit or even another crate.
//
// So because this is a foreign value we blanket apply an external
// linkage directive because it's coming from a different object file.
// The visibility here is where it gets tricky. This symbol could be
// referencing some foreign crate or foreign library (an `extern`
// block) in which case we want to leave the default visibility. We may
// also, though, have multiple codegen units. It could be a
// monomorphization, in which case its expected visibility depends on
// whether we are sharing generics or not. The important thing here is
// that the visibility we apply to the declaration is the same one that
// has been applied to the definition (wherever that definition may be).
let is_generic = instance.substs.non_erasable_generics().next().is_some();
if is_generic {
// This is a monomorphization. Its expected visibility depends
// on whether we are in share-generics mode.
if cx.tcx.sess.opts.share_generics() {
// We are in share_generics mode.
if let Some(instance_def_id) = instance_def_id.as_local() {
// This is a definition from the current crate. If the
// definition is unreachable for downstream crates or
// the current crate does not re-export generics, the
// definition of the instance will have been declared
// as `hidden`.
if cx.tcx.is_unreachable_local_definition(instance_def_id)
|| !cx.tcx.local_crate_exports_generics()
{
#[cfg(feature="master")]
func.add_attribute(FnAttribute::Visibility(Visibility::Hidden));
}
} else {
// This is a monomorphization of a generic function
// defined in an upstream crate.
if instance.upstream_monomorphization(tcx).is_some() {
// This is instantiated in another crate. It cannot
// be `hidden`.
} else {
// This is a local instantiation of an upstream definition.
// If the current crate does not re-export it
// (because it is a C library or an executable), it
// will have been declared `hidden`.
if !cx.tcx.local_crate_exports_generics() {
#[cfg(feature="master")]
func.add_attribute(FnAttribute::Visibility(Visibility::Hidden));
}
}
}
} else {
// When not sharing generics, all instances are in the same
// crate and have hidden visibility
#[cfg(feature="master")]
func.add_attribute(FnAttribute::Visibility(Visibility::Hidden));
}
} else {
// This is a non-generic function
if cx.tcx.is_codegened_item(instance_def_id) {
// This is a function that is instantiated in the local crate
if instance_def_id.is_local() {
// This is function that is defined in the local crate.
// If it is not reachable, it is hidden.
if !cx.tcx.is_reachable_non_generic(instance_def_id) {
#[cfg(feature="master")]
func.add_attribute(FnAttribute::Visibility(Visibility::Hidden));
}
} else {
// This is a function from an upstream crate that has
// been instantiated here. These are always hidden.
#[cfg(feature="master")]
func.add_attribute(FnAttribute::Visibility(Visibility::Hidden));
}
}
}
func
};
cx.function_instances.borrow_mut().insert(instance, func);
func
}
|
