1 //! Codegen the MIR to the LLVM IR.
3 //! Hopefully useful general knowledge about codegen:
5 //! * There's no way to find out the [`Ty`] type of a [`Value`]. Doing so
6 //! would be "trying to get the eggs out of an omelette" (credit:
7 //! pcwalton). You can, instead, find out its [`llvm::Type`] by calling [`val_ty`],
8 //! but one [`llvm::Type`] corresponds to many [`Ty`]s; for instance, `tup(int, int,
9 //! int)` and `rec(x=int, y=int, z=int)` will have the same [`llvm::Type`].
11 //! [`Ty`]: rustc_middle::ty::Ty
12 //! [`val_ty`]: common::val_ty
14 use super::ModuleLlvm;
16 use crate::attributes;
17 use crate::builder::Builder;
19 use crate::context::CodegenCx;
22 use crate::value::Value;
24 use rustc_codegen_ssa::base::maybe_create_entry_wrapper;
25 use rustc_codegen_ssa::mono_item::MonoItemExt;
26 use rustc_codegen_ssa::traits::*;
27 use rustc_codegen_ssa::{ModuleCodegen, ModuleKind};
28 use rustc_data_structures::small_c_str::SmallCStr;
29 use rustc_middle::dep_graph;
30 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
31 use rustc_middle::middle::cstore::EncodedMetadata;
32 use rustc_middle::middle::exported_symbols;
33 use rustc_middle::mir::mono::{Linkage, Visibility};
34 use rustc_middle::ty::TyCtxt;
35 use rustc_session::config::DebugInfo;
36 use rustc_span::symbol::Symbol;
37 use rustc_target::spec::SanitizerSet;
39 use std::ffi::CString;
40 use std::time::Instant;
42 pub fn write_compressed_metadata<'tcx>(
44 metadata: &EncodedMetadata,
45 llvm_module: &mut ModuleLlvm,
47 use snap::write::FrameEncoder;
50 let (metadata_llcx, metadata_llmod) = (&*llvm_module.llcx, llvm_module.llmod());
51 let mut compressed = tcx.metadata_encoding_version();
52 FrameEncoder::new(&mut compressed).write_all(&metadata.raw_data).unwrap();
54 let llmeta = common::bytes_in_context(metadata_llcx, &compressed);
55 let llconst = common::struct_in_context(metadata_llcx, &[llmeta], false);
56 let name = exported_symbols::metadata_symbol_name(tcx);
57 let buf = CString::new(name).unwrap();
59 unsafe { llvm::LLVMAddGlobal(metadata_llmod, common::val_ty(llconst), buf.as_ptr()) };
61 llvm::LLVMSetInitializer(llglobal, llconst);
62 let section_name = metadata::metadata_section_name(&tcx.sess.target);
63 let name = SmallCStr::new(section_name);
64 llvm::LLVMSetSection(llglobal, name.as_ptr());
66 // Also generate a .section directive to force no
67 // flags, at least for ELF outputs, so that the
68 // metadata doesn't get loaded into memory.
69 let directive = format!(".section {}", section_name);
70 llvm::LLVMSetModuleInlineAsm2(metadata_llmod, directive.as_ptr().cast(), directive.len())
74 pub struct ValueIter<'ll> {
75 cur: Option<&'ll Value>,
76 step: unsafe extern "C" fn(&'ll Value) -> Option<&'ll Value>,
79 impl Iterator for ValueIter<'ll> {
80 type Item = &'ll Value;
82 fn next(&mut self) -> Option<&'ll Value> {
84 if let Some(old) = old {
85 self.cur = unsafe { (self.step)(old) };
91 pub fn iter_globals(llmod: &'ll llvm::Module) -> ValueIter<'ll> {
92 unsafe { ValueIter { cur: llvm::LLVMGetFirstGlobal(llmod), step: llvm::LLVMGetNextGlobal } }
95 pub fn compile_codegen_unit(
98 ) -> (ModuleCodegen<ModuleLlvm>, u64) {
99 let start_time = Instant::now();
101 let dep_node = tcx.codegen_unit(cgu_name).codegen_dep_node(tcx);
103 tcx.dep_graph.with_task(dep_node, tcx, cgu_name, module_codegen, dep_graph::hash_result);
104 let time_to_codegen = start_time.elapsed();
106 // We assume that the cost to run LLVM on a CGU is proportional to
107 // the time we needed for codegenning it.
108 let cost = time_to_codegen.as_nanos() as u64;
110 fn module_codegen(tcx: TyCtxt<'_>, cgu_name: Symbol) -> ModuleCodegen<ModuleLlvm> {
111 let cgu = tcx.codegen_unit(cgu_name);
112 let _prof_timer = tcx.prof.generic_activity_with_args(
114 &[cgu_name.to_string(), cgu.size_estimate().to_string()],
116 // Instantiate monomorphizations without filling out definitions yet...
117 let llvm_module = ModuleLlvm::new(tcx, &cgu_name.as_str());
119 let cx = CodegenCx::new(tcx, cgu, &llvm_module);
120 let mono_items = cx.codegen_unit.items_in_deterministic_order(cx.tcx);
121 for &(mono_item, (linkage, visibility)) in &mono_items {
122 mono_item.predefine::<Builder<'_, '_, '_>>(&cx, linkage, visibility);
125 // ... and now that we have everything pre-defined, fill out those definitions.
126 for &(mono_item, _) in &mono_items {
127 mono_item.define::<Builder<'_, '_, '_>>(&cx);
130 // If this codegen unit contains the main function, also create the
132 if let Some(entry) = maybe_create_entry_wrapper::<Builder<'_, '_, '_>>(&cx) {
133 attributes::sanitize(&cx, SanitizerSet::empty(), entry);
136 // Run replace-all-uses-with for statics that need it
137 for &(old_g, new_g) in cx.statics_to_rauw().borrow().iter() {
139 let bitcast = llvm::LLVMConstPointerCast(new_g, cx.val_ty(old_g));
140 llvm::LLVMReplaceAllUsesWith(old_g, bitcast);
141 llvm::LLVMDeleteGlobal(old_g);
145 // Finalize code coverage by injecting the coverage map. Note, the coverage map will
146 // also be added to the `llvm.used` variable, created next.
147 if cx.sess().instrument_coverage() {
148 cx.coverageinfo_finalize();
151 // Create the llvm.used variable
152 // This variable has type [N x i8*] and is stored in the llvm.metadata section
153 if !cx.used_statics().borrow().is_empty() {
154 cx.create_used_variable()
157 // Finalize debuginfo
158 if cx.sess().opts.debuginfo != DebugInfo::None {
159 cx.debuginfo_finalize();
164 name: cgu_name.to_string(),
165 module_llvm: llvm_module,
166 kind: ModuleKind::Regular,
173 pub fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
174 let sect = match attrs.link_section {
179 let buf = SmallCStr::new(§.as_str());
180 llvm::LLVMSetSection(llval, buf.as_ptr());
184 pub fn linkage_to_llvm(linkage: Linkage) -> llvm::Linkage {
186 Linkage::External => llvm::Linkage::ExternalLinkage,
187 Linkage::AvailableExternally => llvm::Linkage::AvailableExternallyLinkage,
188 Linkage::LinkOnceAny => llvm::Linkage::LinkOnceAnyLinkage,
189 Linkage::LinkOnceODR => llvm::Linkage::LinkOnceODRLinkage,
190 Linkage::WeakAny => llvm::Linkage::WeakAnyLinkage,
191 Linkage::WeakODR => llvm::Linkage::WeakODRLinkage,
192 Linkage::Appending => llvm::Linkage::AppendingLinkage,
193 Linkage::Internal => llvm::Linkage::InternalLinkage,
194 Linkage::Private => llvm::Linkage::PrivateLinkage,
195 Linkage::ExternalWeak => llvm::Linkage::ExternalWeakLinkage,
196 Linkage::Common => llvm::Linkage::CommonLinkage,
200 pub fn visibility_to_llvm(linkage: Visibility) -> llvm::Visibility {
202 Visibility::Default => llvm::Visibility::Default,
203 Visibility::Hidden => llvm::Visibility::Hidden,
204 Visibility::Protected => llvm::Visibility::Protected,