rustc_codegen_llvm/
allocator.rs

1use libc::c_uint;
2use rustc_ast::expand::allocator::{
3    ALLOCATOR_METHODS, AllocatorKind, AllocatorTy, NO_ALLOC_SHIM_IS_UNSTABLE,
4    alloc_error_handler_name, default_fn_name, global_fn_name,
5};
6use rustc_codegen_ssa::traits::BaseTypeCodegenMethods as _;
7use rustc_middle::bug;
8use rustc_middle::ty::TyCtxt;
9use rustc_session::config::{DebugInfo, OomStrategy};
10use rustc_symbol_mangling::mangle_internal_symbol;
11
12use crate::builder::SBuilder;
13use crate::declare::declare_simple_fn;
14use crate::llvm::{self, False, True, Type, Value};
15use crate::{SimpleCx, attributes, debuginfo};
16
17pub(crate) unsafe fn codegen(
18    tcx: TyCtxt<'_>,
19    cx: SimpleCx<'_>,
20    module_name: &str,
21    kind: AllocatorKind,
22    alloc_error_handler_kind: AllocatorKind,
23) {
24    let usize = match tcx.sess.target.pointer_width {
25        16 => cx.type_i16(),
26        32 => cx.type_i32(),
27        64 => cx.type_i64(),
28        tws => bug!("Unsupported target word size for int: {}", tws),
29    };
30    let i8 = cx.type_i8();
31    let i8p = cx.type_ptr();
32
33    if kind == AllocatorKind::Default {
34        for method in ALLOCATOR_METHODS {
35            let mut args = Vec::with_capacity(method.inputs.len());
36            for input in method.inputs.iter() {
37                match input.ty {
38                    AllocatorTy::Layout => {
39                        args.push(usize); // size
40                        args.push(usize); // align
41                    }
42                    AllocatorTy::Ptr => args.push(i8p),
43                    AllocatorTy::Usize => args.push(usize),
44
45                    AllocatorTy::ResultPtr | AllocatorTy::Unit => panic!("invalid allocator arg"),
46                }
47            }
48            let output = match method.output {
49                AllocatorTy::ResultPtr => Some(i8p),
50                AllocatorTy::Unit => None,
51
52                AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
53                    panic!("invalid allocator output")
54                }
55            };
56
57            let from_name = mangle_internal_symbol(tcx, &global_fn_name(method.name));
58            let to_name = mangle_internal_symbol(tcx, &default_fn_name(method.name));
59
60            create_wrapper_function(tcx, &cx, &from_name, Some(&to_name), &args, output, false);
61        }
62    }
63
64    // rust alloc error handler
65    create_wrapper_function(
66        tcx,
67        &cx,
68        &mangle_internal_symbol(tcx, "__rust_alloc_error_handler"),
69        Some(&mangle_internal_symbol(tcx, alloc_error_handler_name(alloc_error_handler_kind))),
70        &[usize, usize], // size, align
71        None,
72        true,
73    );
74
75    unsafe {
76        // __rust_alloc_error_handler_should_panic_v2
77        create_const_value_function(
78            tcx,
79            &cx,
80            &mangle_internal_symbol(tcx, OomStrategy::SYMBOL),
81            &i8,
82            &llvm::LLVMConstInt(i8, tcx.sess.opts.unstable_opts.oom.should_panic() as u64, False),
83        );
84
85        // __rust_no_alloc_shim_is_unstable_v2
86        create_wrapper_function(
87            tcx,
88            &cx,
89            &mangle_internal_symbol(tcx, NO_ALLOC_SHIM_IS_UNSTABLE),
90            None,
91            &[],
92            None,
93            false,
94        );
95    }
96
97    if tcx.sess.opts.debuginfo != DebugInfo::None {
98        let dbg_cx = debuginfo::CodegenUnitDebugContext::new(cx.llmod);
99        debuginfo::metadata::build_compile_unit_di_node(tcx, module_name, &dbg_cx);
100        dbg_cx.finalize(tcx.sess);
101    }
102}
103
104fn create_const_value_function(
105    tcx: TyCtxt<'_>,
106    cx: &SimpleCx<'_>,
107    name: &str,
108    output: &Type,
109    value: &Value,
110) {
111    let ty = cx.type_func(&[], output);
112    let llfn = declare_simple_fn(
113        &cx,
114        name,
115        llvm::CallConv::CCallConv,
116        llvm::UnnamedAddr::Global,
117        llvm::Visibility::from_generic(tcx.sess.default_visibility()),
118        ty,
119    );
120
121    attributes::apply_to_llfn(
122        llfn,
123        llvm::AttributePlace::Function,
124        &[llvm::AttributeKind::AlwaysInline.create_attr(cx.llcx)],
125    );
126
127    let llbb = unsafe { llvm::LLVMAppendBasicBlockInContext(cx.llcx, llfn, c"entry".as_ptr()) };
128    let mut bx = SBuilder::build(&cx, llbb);
129    bx.ret(value);
130}
131
132fn create_wrapper_function(
133    tcx: TyCtxt<'_>,
134    cx: &SimpleCx<'_>,
135    from_name: &str,
136    to_name: Option<&str>,
137    args: &[&Type],
138    output: Option<&Type>,
139    no_return: bool,
140) {
141    let ty = cx.type_func(args, output.unwrap_or_else(|| cx.type_void()));
142    let llfn = declare_simple_fn(
143        &cx,
144        from_name,
145        llvm::CallConv::CCallConv,
146        llvm::UnnamedAddr::Global,
147        llvm::Visibility::from_generic(tcx.sess.default_visibility()),
148        ty,
149    );
150    let no_return = if no_return {
151        // -> ! DIFlagNoReturn
152        let no_return = llvm::AttributeKind::NoReturn.create_attr(cx.llcx);
153        attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[no_return]);
154        Some(no_return)
155    } else {
156        None
157    };
158
159    if tcx.sess.must_emit_unwind_tables() {
160        let uwtable =
161            attributes::uwtable_attr(cx.llcx, tcx.sess.opts.unstable_opts.use_sync_unwind);
162        attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
163    }
164
165    let llbb = unsafe { llvm::LLVMAppendBasicBlockInContext(cx.llcx, llfn, c"entry".as_ptr()) };
166    let mut bx = SBuilder::build(&cx, llbb);
167
168    if let Some(to_name) = to_name {
169        let callee = declare_simple_fn(
170            &cx,
171            to_name,
172            llvm::CallConv::CCallConv,
173            llvm::UnnamedAddr::Global,
174            llvm::Visibility::Hidden,
175            ty,
176        );
177        if let Some(no_return) = no_return {
178            // -> ! DIFlagNoReturn
179            attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);
180        }
181        llvm::set_visibility(callee, llvm::Visibility::Hidden);
182
183        let args = args
184            .iter()
185            .enumerate()
186            .map(|(i, _)| llvm::get_param(llfn, i as c_uint))
187            .collect::<Vec<_>>();
188        let ret = bx.call(ty, callee, &args, None);
189        llvm::LLVMSetTailCall(ret, True);
190        if output.is_some() {
191            bx.ret(ret);
192        } else {
193            bx.ret_void()
194        }
195    } else {
196        assert!(output.is_none());
197        bx.ret_void()
198    }
199}
rustc_codegen_llvm/allocator.rs

rustc_codegen_llvm/
allocator.rs
