1 //! Codegen the completed AST to the LLVM IR.
3 //! Some functions here, such as codegen_block and codegen_expr, return a value --
4 //! the result of the codegen to LLVM -- while others, such as codegen_fn
5 //! and mono_item, are called only for the side effect of adding a
6 //! particular definition to the LLVM IR output we're producing.
8 //! Hopefully useful general knowledge about codegen:
10 //! * There's no way to find out the `Ty` type of a Value. Doing so
11 //! would be "trying to get the eggs out of an omelette" (credit:
12 //! pcwalton). You can, instead, find out its `llvm::Type` by calling `val_ty`,
13 //! but one `llvm::Type` corresponds to many `Ty`s; for instance, `tup(int, int,
14 //! int)` and `rec(x=int, y=int, z=int)` will have the same `llvm::Type`.
16 use super::{LlvmCodegenBackend, ModuleLlvm};
18 use crate::builder::Builder;
20 use crate::context::CodegenCx;
23 use crate::value::Value;
26 use rustc::middle::codegen_fn_attrs::CodegenFnAttrs;
27 use rustc::middle::cstore::EncodedMetadata;
28 use rustc::middle::exported_symbols;
29 use rustc::mir::mono::{Linkage, Visibility};
30 use rustc::session::config::DebugInfo;
31 use rustc::ty::TyCtxt;
32 use rustc_codegen_ssa::back::write::submit_codegened_module_to_llvm;
33 use rustc_codegen_ssa::base::maybe_create_entry_wrapper;
34 use rustc_codegen_ssa::mono_item::MonoItemExt;
35 use rustc_codegen_ssa::traits::*;
36 use rustc_codegen_ssa::{ModuleCodegen, ModuleKind};
37 use rustc_data_structures::small_c_str::SmallCStr;
38 use rustc_span::symbol::Symbol;
40 use std::ffi::CString;
41 use std::time::Instant;
43 pub fn write_compressed_metadata<'tcx>(
45 metadata: &EncodedMetadata,
46 llvm_module: &mut ModuleLlvm,
48 use flate2::write::DeflateEncoder;
49 use flate2::Compression;
52 let (metadata_llcx, metadata_llmod) = (&*llvm_module.llcx, llvm_module.llmod());
53 let mut compressed = tcx.metadata_encoding_version();
54 DeflateEncoder::new(&mut compressed, Compression::fast())
55 .write_all(&metadata.raw_data)
58 let llmeta = common::bytes_in_context(metadata_llcx, &compressed);
59 let llconst = common::struct_in_context(metadata_llcx, &[llmeta], false);
60 let name = exported_symbols::metadata_symbol_name(tcx);
61 let buf = CString::new(name).unwrap();
63 unsafe { llvm::LLVMAddGlobal(metadata_llmod, common::val_ty(llconst), buf.as_ptr()) };
65 llvm::LLVMSetInitializer(llglobal, llconst);
66 let section_name = metadata::metadata_section_name(&tcx.sess.target.target);
67 let name = SmallCStr::new(section_name);
68 llvm::LLVMSetSection(llglobal, name.as_ptr());
70 // Also generate a .section directive to force no
71 // flags, at least for ELF outputs, so that the
72 // metadata doesn't get loaded into memory.
73 let directive = format!(".section {}", section_name);
74 let directive = CString::new(directive).unwrap();
75 llvm::LLVMSetModuleInlineAsm(metadata_llmod, directive.as_ptr())
79 pub struct ValueIter<'ll> {
80 cur: Option<&'ll Value>,
81 step: unsafe extern "C" fn(&'ll Value) -> Option<&'ll Value>,
84 impl Iterator for ValueIter<'ll> {
85 type Item = &'ll Value;
87 fn next(&mut self) -> Option<&'ll Value> {
89 if let Some(old) = old {
90 self.cur = unsafe { (self.step)(old) };
96 pub fn iter_globals(llmod: &'ll llvm::Module) -> ValueIter<'ll> {
97 unsafe { ValueIter { cur: llvm::LLVMGetFirstGlobal(llmod), step: llvm::LLVMGetNextGlobal } }
100 pub fn compile_codegen_unit(
103 tx_to_llvm_workers: &std::sync::mpsc::Sender<Box<dyn std::any::Any + Send>>,
105 let prof_timer = tcx.prof.generic_activity("codegen_module");
106 let start_time = Instant::now();
108 let dep_node = tcx.codegen_unit(cgu_name).codegen_dep_node(tcx);
110 tcx.dep_graph.with_task(dep_node, tcx, cgu_name, module_codegen, dep_graph::hash_result);
111 let time_to_codegen = start_time.elapsed();
114 // We assume that the cost to run LLVM on a CGU is proportional to
115 // the time we needed for codegenning it.
116 let cost = time_to_codegen.as_secs() * 1_000_000_000 + time_to_codegen.subsec_nanos() as u64;
118 submit_codegened_module_to_llvm(&LlvmCodegenBackend(()), tx_to_llvm_workers, module, cost);
120 fn module_codegen(tcx: TyCtxt<'_>, cgu_name: Symbol) -> ModuleCodegen<ModuleLlvm> {
121 let cgu = tcx.codegen_unit(cgu_name);
122 // Instantiate monomorphizations without filling out definitions yet...
123 let llvm_module = ModuleLlvm::new(tcx, &cgu_name.as_str());
125 let cx = CodegenCx::new(tcx, cgu, &llvm_module);
126 let mono_items = cx.codegen_unit.items_in_deterministic_order(cx.tcx);
127 for &(mono_item, (linkage, visibility)) in &mono_items {
128 mono_item.predefine::<Builder<'_, '_, '_>>(&cx, linkage, visibility);
131 // ... and now that we have everything pre-defined, fill out those definitions.
132 for &(mono_item, _) in &mono_items {
133 mono_item.define::<Builder<'_, '_, '_>>(&cx);
136 // If this codegen unit contains the main function, also create the
138 maybe_create_entry_wrapper::<Builder<'_, '_, '_>>(&cx);
140 // Run replace-all-uses-with for statics that need it
141 for &(old_g, new_g) in cx.statics_to_rauw().borrow().iter() {
143 let bitcast = llvm::LLVMConstPointerCast(new_g, cx.val_ty(old_g));
144 llvm::LLVMReplaceAllUsesWith(old_g, bitcast);
145 llvm::LLVMDeleteGlobal(old_g);
149 // Create the llvm.used variable
150 // This variable has type [N x i8*] and is stored in the llvm.metadata section
151 if !cx.used_statics().borrow().is_empty() {
152 cx.create_used_variable()
155 // Finalize debuginfo
156 if cx.sess().opts.debuginfo != DebugInfo::None {
157 cx.debuginfo_finalize();
162 name: cgu_name.to_string(),
163 module_llvm: llvm_module,
164 kind: ModuleKind::Regular,
169 pub fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
170 let sect = match attrs.link_section {
175 let buf = SmallCStr::new(§.as_str());
176 llvm::LLVMSetSection(llval, buf.as_ptr());
180 pub fn linkage_to_llvm(linkage: Linkage) -> llvm::Linkage {
182 Linkage::External => llvm::Linkage::ExternalLinkage,
183 Linkage::AvailableExternally => llvm::Linkage::AvailableExternallyLinkage,
184 Linkage::LinkOnceAny => llvm::Linkage::LinkOnceAnyLinkage,
185 Linkage::LinkOnceODR => llvm::Linkage::LinkOnceODRLinkage,
186 Linkage::WeakAny => llvm::Linkage::WeakAnyLinkage,
187 Linkage::WeakODR => llvm::Linkage::WeakODRLinkage,
188 Linkage::Appending => llvm::Linkage::AppendingLinkage,
189 Linkage::Internal => llvm::Linkage::InternalLinkage,
190 Linkage::Private => llvm::Linkage::PrivateLinkage,
191 Linkage::ExternalWeak => llvm::Linkage::ExternalWeakLinkage,
192 Linkage::Common => llvm::Linkage::CommonLinkage,
196 pub fn visibility_to_llvm(linkage: Visibility) -> llvm::Visibility {
198 Visibility::Default => llvm::Visibility::Default,
199 Visibility::Hidden => llvm::Visibility::Hidden,
200 Visibility::Protected => llvm::Visibility::Protected,