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353b0b11 FG |
1 | #[cfg(feature="master")] |
2 | use gccjit::{FnAttribute, Visibility}; | |
3 | use gccjit::{FunctionType, Function}; | |
9ffffee4 | 4 | use rustc_middle::ty::{self, Instance, TypeVisitableExt}; |
c295e0f8 XL |
5 | use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt}; |
6 | ||
353b0b11 | 7 | use crate::attributes; |
c295e0f8 XL |
8 | use crate::context::CodegenCx; |
9 | ||
10 | /// Codegens a reference to a fn/method item, monomorphizing and | |
11 | /// inlining as it goes. | |
12 | /// | |
13 | /// # Parameters | |
14 | /// | |
15 | /// - `cx`: the crate context | |
16 | /// - `instance`: the instance to be instantiated | |
353b0b11 | 17 | pub fn get_fn<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, instance: Instance<'tcx>) -> Function<'gcc> { |
c295e0f8 XL |
18 | let tcx = cx.tcx(); |
19 | ||
20 | assert!(!instance.substs.needs_infer()); | |
21 | assert!(!instance.substs.has_escaping_bound_vars()); | |
22 | ||
353b0b11 FG |
23 | let sym = tcx.symbol_name(instance).name; |
24 | ||
c295e0f8 XL |
25 | if let Some(&func) = cx.function_instances.borrow().get(&instance) { |
26 | return func; | |
27 | } | |
28 | ||
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29 | let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty()); |
30 | ||
31 | let func = | |
353b0b11 FG |
32 | if let Some(_func) = cx.get_declared_value(&sym) { |
33 | // FIXME(antoyo): we never reach this because get_declared_value only returns global variables | |
34 | // and here we try to get a function. | |
35 | unreachable!(); | |
36 | /* | |
c295e0f8 XL |
37 | // Create a fn pointer with the new signature. |
38 | let ptrty = fn_abi.ptr_to_gcc_type(cx); | |
39 | ||
40 | // This is subtle and surprising, but sometimes we have to bitcast | |
41 | // the resulting fn pointer. The reason has to do with external | |
42 | // functions. If you have two crates that both bind the same C | |
43 | // library, they may not use precisely the same types: for | |
44 | // example, they will probably each declare their own structs, | |
45 | // which are distinct types from LLVM's point of view (nominal | |
46 | // types). | |
47 | // | |
48 | // Now, if those two crates are linked into an application, and | |
49 | // they contain inlined code, you can wind up with a situation | |
50 | // where both of those functions wind up being loaded into this | |
51 | // application simultaneously. In that case, the same function | |
52 | // (from LLVM's point of view) requires two types. But of course | |
53 | // LLVM won't allow one function to have two types. | |
54 | // | |
55 | // What we currently do, therefore, is declare the function with | |
56 | // one of the two types (whichever happens to come first) and then | |
57 | // bitcast as needed when the function is referenced to make sure | |
58 | // it has the type we expect. | |
59 | // | |
60 | // This can occur on either a crate-local or crate-external | |
61 | // reference. It also occurs when testing libcore and in some | |
62 | // other weird situations. Annoying. | |
63 | if cx.val_ty(func) != ptrty { | |
64 | // TODO(antoyo): cast the pointer. | |
65 | func | |
66 | } | |
67 | else { | |
68 | func | |
353b0b11 | 69 | }*/ |
c295e0f8 XL |
70 | } |
71 | else { | |
72 | cx.linkage.set(FunctionType::Extern); | |
73 | let func = cx.declare_fn(&sym, &fn_abi); | |
74 | ||
353b0b11 FG |
75 | attributes::from_fn_attrs(cx, func, instance); |
76 | ||
77 | let instance_def_id = instance.def_id(); | |
78 | ||
c295e0f8 | 79 | // TODO(antoyo): set linkage and attributes. |
353b0b11 FG |
80 | |
81 | // Apply an appropriate linkage/visibility value to our item that we | |
82 | // just declared. | |
83 | // | |
84 | // This is sort of subtle. Inside our codegen unit we started off | |
85 | // compilation by predefining all our own `MonoItem` instances. That | |
86 | // is, everything we're codegenning ourselves is already defined. That | |
87 | // means that anything we're actually codegenning in this codegen unit | |
88 | // will have hit the above branch in `get_declared_value`. As a result, | |
89 | // we're guaranteed here that we're declaring a symbol that won't get | |
90 | // defined, or in other words we're referencing a value from another | |
91 | // codegen unit or even another crate. | |
92 | // | |
93 | // So because this is a foreign value we blanket apply an external | |
94 | // linkage directive because it's coming from a different object file. | |
95 | // The visibility here is where it gets tricky. This symbol could be | |
96 | // referencing some foreign crate or foreign library (an `extern` | |
97 | // block) in which case we want to leave the default visibility. We may | |
98 | // also, though, have multiple codegen units. It could be a | |
99 | // monomorphization, in which case its expected visibility depends on | |
100 | // whether we are sharing generics or not. The important thing here is | |
101 | // that the visibility we apply to the declaration is the same one that | |
102 | // has been applied to the definition (wherever that definition may be). | |
103 | let is_generic = instance.substs.non_erasable_generics().next().is_some(); | |
104 | ||
105 | if is_generic { | |
106 | // This is a monomorphization. Its expected visibility depends | |
107 | // on whether we are in share-generics mode. | |
108 | ||
109 | if cx.tcx.sess.opts.share_generics() { | |
110 | // We are in share_generics mode. | |
111 | ||
112 | if let Some(instance_def_id) = instance_def_id.as_local() { | |
113 | // This is a definition from the current crate. If the | |
114 | // definition is unreachable for downstream crates or | |
115 | // the current crate does not re-export generics, the | |
116 | // definition of the instance will have been declared | |
117 | // as `hidden`. | |
118 | if cx.tcx.is_unreachable_local_definition(instance_def_id) | |
119 | || !cx.tcx.local_crate_exports_generics() | |
120 | { | |
121 | #[cfg(feature="master")] | |
122 | func.add_attribute(FnAttribute::Visibility(Visibility::Hidden)); | |
123 | } | |
124 | } else { | |
125 | // This is a monomorphization of a generic function | |
126 | // defined in an upstream crate. | |
127 | if instance.upstream_monomorphization(tcx).is_some() { | |
128 | // This is instantiated in another crate. It cannot | |
129 | // be `hidden`. | |
130 | } else { | |
131 | // This is a local instantiation of an upstream definition. | |
132 | // If the current crate does not re-export it | |
133 | // (because it is a C library or an executable), it | |
134 | // will have been declared `hidden`. | |
135 | if !cx.tcx.local_crate_exports_generics() { | |
136 | #[cfg(feature="master")] | |
137 | func.add_attribute(FnAttribute::Visibility(Visibility::Hidden)); | |
138 | } | |
139 | } | |
140 | } | |
141 | } else { | |
142 | // When not sharing generics, all instances are in the same | |
143 | // crate and have hidden visibility | |
144 | #[cfg(feature="master")] | |
145 | func.add_attribute(FnAttribute::Visibility(Visibility::Hidden)); | |
146 | } | |
147 | } else { | |
148 | // This is a non-generic function | |
149 | if cx.tcx.is_codegened_item(instance_def_id) { | |
150 | // This is a function that is instantiated in the local crate | |
151 | ||
152 | if instance_def_id.is_local() { | |
153 | // This is function that is defined in the local crate. | |
154 | // If it is not reachable, it is hidden. | |
155 | if !cx.tcx.is_reachable_non_generic(instance_def_id) { | |
156 | #[cfg(feature="master")] | |
157 | func.add_attribute(FnAttribute::Visibility(Visibility::Hidden)); | |
158 | } | |
159 | } else { | |
160 | // This is a function from an upstream crate that has | |
161 | // been instantiated here. These are always hidden. | |
162 | #[cfg(feature="master")] | |
163 | func.add_attribute(FnAttribute::Visibility(Visibility::Hidden)); | |
164 | } | |
165 | } | |
166 | } | |
167 | ||
c295e0f8 XL |
168 | func |
169 | }; | |
170 | ||
171 | cx.function_instances.borrow_mut().insert(instance, func); | |
172 | ||
173 | func | |
174 | } |