rustc_codegen_llvm/
allocator.rs

1use libc::c_uint;
2use rustc_ast::expand::allocator::{
3    AllocatorMethod, AllocatorTy, NO_ALLOC_SHIM_IS_UNSTABLE, SpecialAllocatorMethod,
4    default_fn_name, global_fn_name,
5};
6use rustc_codegen_ssa::traits::BaseTypeCodegenMethods as _;
7use rustc_middle::bug;
8use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
9use rustc_middle::ty::TyCtxt;
10use rustc_session::config::DebugInfo;
11use rustc_symbol_mangling::mangle_internal_symbol;
12
13use crate::attributes::llfn_attrs_from_instance;
14use crate::builder::SBuilder;
15use crate::declare::declare_simple_fn;
16use crate::llvm::{self, FromGeneric, TRUE, Type};
17use crate::{SimpleCx, attributes, debuginfo};
18
19pub(crate) unsafe fn codegen(
20    tcx: TyCtxt<'_>,
21    cx: SimpleCx<'_>,
22    module_name: &str,
23    methods: &[AllocatorMethod],
24) {
25    let usize = match tcx.sess.target.pointer_width {
26        16 => cx.type_i16(),
27        32 => cx.type_i32(),
28        64 => cx.type_i64(),
29        tws => bug!("Unsupported target word size for int: {}", tws),
30    };
31    let i8p = cx.type_ptr();
32
33    for method in methods {
34        let mut args = Vec::with_capacity(method.inputs.len());
35        for input in method.inputs.iter() {
36            match input.ty {
37                AllocatorTy::Layout => {
38                    args.push(usize); // size
39                    args.push(usize); // align
40                }
41                AllocatorTy::Ptr => args.push(i8p),
42                AllocatorTy::Usize => args.push(usize),
43
44                AllocatorTy::Never | AllocatorTy::ResultPtr | AllocatorTy::Unit => {
45                    panic!("invalid allocator arg")
46                }
47            }
48        }
49
50        let mut no_return = false;
51        let output = match method.output {
52            AllocatorTy::ResultPtr => Some(i8p),
53            AllocatorTy::Unit => None,
54            AllocatorTy::Never => {
55                no_return = true;
56                None
57            }
58
59            AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
60                panic!("invalid allocator output")
61            }
62        };
63
64        let from_name = mangle_internal_symbol(tcx, &global_fn_name(method.name));
65        let to_name = mangle_internal_symbol(tcx, &default_fn_name(method.name));
66
67        let alloc_attr_flag = match method.special {
68            Some(SpecialAllocatorMethod::Alloc) => CodegenFnAttrFlags::ALLOCATOR,
69            Some(SpecialAllocatorMethod::Dealloc) => CodegenFnAttrFlags::DEALLOCATOR,
70            Some(SpecialAllocatorMethod::Realloc) => CodegenFnAttrFlags::REALLOCATOR,
71            Some(SpecialAllocatorMethod::AllocZeroed) => CodegenFnAttrFlags::ALLOCATOR_ZEROED,
72            None => CodegenFnAttrFlags::empty(),
73        };
74
75        let mut attrs = CodegenFnAttrs::new();
76        attrs.flags |= alloc_attr_flag;
77        create_wrapper_function(
78            tcx,
79            &cx,
80            &from_name,
81            Some(&to_name),
82            &args,
83            output,
84            no_return,
85            &attrs,
86        );
87    }
88
89    // __rust_no_alloc_shim_is_unstable_v2
90    create_wrapper_function(
91        tcx,
92        &cx,
93        &mangle_internal_symbol(tcx, NO_ALLOC_SHIM_IS_UNSTABLE),
94        None,
95        &[],
96        None,
97        false,
98        &CodegenFnAttrs::new(),
99    );
100
101    if tcx.sess.opts.debuginfo != DebugInfo::None {
102        let dbg_cx = debuginfo::CodegenUnitDebugContext::new(cx.llmod);
103        debuginfo::metadata::build_compile_unit_di_node(tcx, module_name, &dbg_cx);
104        dbg_cx.finalize(tcx.sess);
105    }
106}
107
108fn create_wrapper_function(
109    tcx: TyCtxt<'_>,
110    cx: &SimpleCx<'_>,
111    from_name: &str,
112    to_name: Option<&str>,
113    args: &[&Type],
114    output: Option<&Type>,
115    no_return: bool,
116    attrs: &CodegenFnAttrs,
117) {
118    let ty = cx.type_func(args, output.unwrap_or_else(|| cx.type_void()));
119    let llfn = declare_simple_fn(
120        &cx,
121        from_name,
122        llvm::CallConv::CCallConv,
123        llvm::UnnamedAddr::Global,
124        llvm::Visibility::from_generic(tcx.sess.default_visibility()),
125        ty,
126    );
127
128    llfn_attrs_from_instance(cx, tcx, llfn, attrs, None);
129
130    let no_return = if no_return {
131        // -> ! DIFlagNoReturn
132        let no_return = llvm::AttributeKind::NoReturn.create_attr(cx.llcx);
133        attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[no_return]);
134        Some(no_return)
135    } else {
136        None
137    };
138
139    let llbb = unsafe { llvm::LLVMAppendBasicBlockInContext(cx.llcx, llfn, c"entry".as_ptr()) };
140    let mut bx = SBuilder::build(&cx, llbb);
141
142    if let Some(to_name) = to_name {
143        let callee = declare_simple_fn(
144            &cx,
145            to_name,
146            llvm::CallConv::CCallConv,
147            llvm::UnnamedAddr::Global,
148            llvm::Visibility::Hidden,
149            ty,
150        );
151        if let Some(no_return) = no_return {
152            // -> ! DIFlagNoReturn
153            attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);
154        }
155        llvm::set_visibility(callee, llvm::Visibility::Hidden);
156
157        let args = args
158            .iter()
159            .enumerate()
160            .map(|(i, _)| llvm::get_param(llfn, i as c_uint))
161            .collect::<Vec<_>>();
162        let ret = bx.call(ty, callee, &args, None);
163        llvm::LLVMSetTailCall(ret, TRUE);
164        if output.is_some() {
165            bx.ret(ret);
166        } else {
167            bx.ret_void()
168        }
169    } else {
170        assert!(output.is_none());
171        bx.ret_void()
172    }
173}
rustc_codegen_llvm/allocator.rs

rustc_codegen_llvm/
allocator.rs
