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;
21 use crate::value::Value;
23 use rustc_codegen_ssa::base::maybe_create_entry_wrapper;
24 use rustc_codegen_ssa::mono_item::MonoItemExt;
25 use rustc_codegen_ssa::traits::*;
26 use rustc_codegen_ssa::{ModuleCodegen, ModuleKind};
27 use rustc_data_structures::small_c_str::SmallCStr;
28 use rustc_middle::dep_graph;
29 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
30 use rustc_middle::middle::cstore::EncodedMetadata;
31 use rustc_middle::middle::exported_symbols;
32 use rustc_middle::mir::mono::{Linkage, Visibility};
33 use rustc_middle::ty::TyCtxt;
34 use rustc_session::config::DebugInfo;
35 use rustc_span::symbol::Symbol;
36 use rustc_target::spec::SanitizerSet;
38 use std::ffi::CString;
39 use std::time::Instant;
41 pub fn write_compressed_metadata<'tcx>(
43 metadata: &EncodedMetadata,
44 llvm_module: &mut ModuleLlvm,
46 use snap::write::FrameEncoder;
51 // When using link.exe it was seen that the section name `.note.rustc`
52 // was getting shortened to `.note.ru`, and according to the PE and COFF
55 // > Executable images do not use a string table and do not support
56 // > section names longer than 8 characters
58 // https://docs.microsoft.com/en-us/windows/win32/debug/pe-format
60 // As a result, we choose a slightly shorter name! As to why
61 // `.note.rustc` works on MinGW, see
62 // https://github.com/llvm/llvm-project/blob/llvmorg-12.0.0/lld/COFF/Writer.cpp#L1190-L1197
63 let section_name = if tcx.sess.target.is_like_osx { "__DATA,.rustc" } else { ".rustc" };
65 let (metadata_llcx, metadata_llmod) = (&*llvm_module.llcx, llvm_module.llmod());
66 let mut compressed = rustc_metadata::METADATA_HEADER.to_vec();
67 FrameEncoder::new(&mut compressed).write_all(&metadata.raw_data).unwrap();
69 let llmeta = common::bytes_in_context(metadata_llcx, &compressed);
70 let llconst = common::struct_in_context(metadata_llcx, &[llmeta], false);
71 let name = exported_symbols::metadata_symbol_name(tcx);
72 let buf = CString::new(name).unwrap();
74 unsafe { llvm::LLVMAddGlobal(metadata_llmod, common::val_ty(llconst), buf.as_ptr()) };
76 llvm::LLVMSetInitializer(llglobal, llconst);
77 let name = SmallCStr::new(section_name);
78 llvm::LLVMSetSection(llglobal, name.as_ptr());
80 // Also generate a .section directive to force no
81 // flags, at least for ELF outputs, so that the
82 // metadata doesn't get loaded into memory.
83 let directive = format!(".section {}", section_name);
84 llvm::LLVMSetModuleInlineAsm2(metadata_llmod, directive.as_ptr().cast(), directive.len())
88 pub struct ValueIter<'ll> {
89 cur: Option<&'ll Value>,
90 step: unsafe extern "C" fn(&'ll Value) -> Option<&'ll Value>,
93 impl Iterator for ValueIter<'ll> {
94 type Item = &'ll Value;
96 fn next(&mut self) -> Option<&'ll Value> {
98 if let Some(old) = old {
99 self.cur = unsafe { (self.step)(old) };
105 pub fn iter_globals(llmod: &'ll llvm::Module) -> ValueIter<'ll> {
106 unsafe { ValueIter { cur: llvm::LLVMGetFirstGlobal(llmod), step: llvm::LLVMGetNextGlobal } }
109 pub fn compile_codegen_unit(
112 ) -> (ModuleCodegen<ModuleLlvm>, u64) {
113 let start_time = Instant::now();
115 let dep_node = tcx.codegen_unit(cgu_name).codegen_dep_node(tcx);
117 tcx.dep_graph.with_task(dep_node, tcx, cgu_name, module_codegen, dep_graph::hash_result);
118 let time_to_codegen = start_time.elapsed();
120 // We assume that the cost to run LLVM on a CGU is proportional to
121 // the time we needed for codegenning it.
122 let cost = time_to_codegen.as_nanos() as u64;
124 fn module_codegen(tcx: TyCtxt<'_>, cgu_name: Symbol) -> ModuleCodegen<ModuleLlvm> {
125 let cgu = tcx.codegen_unit(cgu_name);
126 let _prof_timer = tcx.prof.generic_activity_with_args(
128 &[cgu_name.to_string(), cgu.size_estimate().to_string()],
130 // Instantiate monomorphizations without filling out definitions yet...
131 let llvm_module = ModuleLlvm::new(tcx, &cgu_name.as_str());
133 let cx = CodegenCx::new(tcx, cgu, &llvm_module);
134 let mono_items = cx.codegen_unit.items_in_deterministic_order(cx.tcx);
135 for &(mono_item, (linkage, visibility)) in &mono_items {
136 mono_item.predefine::<Builder<'_, '_, '_>>(&cx, linkage, visibility);
139 // ... and now that we have everything pre-defined, fill out those definitions.
140 for &(mono_item, _) in &mono_items {
141 mono_item.define::<Builder<'_, '_, '_>>(&cx);
144 // If this codegen unit contains the main function, also create the
146 if let Some(entry) = maybe_create_entry_wrapper::<Builder<'_, '_, '_>>(&cx) {
147 attributes::sanitize(&cx, SanitizerSet::empty(), entry);
150 // Run replace-all-uses-with for statics that need it
151 for &(old_g, new_g) in cx.statics_to_rauw().borrow().iter() {
153 let bitcast = llvm::LLVMConstPointerCast(new_g, cx.val_ty(old_g));
154 llvm::LLVMReplaceAllUsesWith(old_g, bitcast);
155 llvm::LLVMDeleteGlobal(old_g);
159 // Finalize code coverage by injecting the coverage map. Note, the coverage map will
160 // also be added to the `llvm.compiler.used` variable, created next.
161 if cx.sess().instrument_coverage() {
162 cx.coverageinfo_finalize();
165 // Create the llvm.used and llvm.compiler.used variables.
166 if !cx.used_statics().borrow().is_empty() {
167 cx.create_used_variable()
169 if !cx.compiler_used_statics().borrow().is_empty() {
170 cx.create_compiler_used_variable()
173 // Finalize debuginfo
174 if cx.sess().opts.debuginfo != DebugInfo::None {
175 cx.debuginfo_finalize();
180 name: cgu_name.to_string(),
181 module_llvm: llvm_module,
182 kind: ModuleKind::Regular,
189 pub fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
190 let sect = match attrs.link_section {
195 let buf = SmallCStr::new(§.as_str());
196 llvm::LLVMSetSection(llval, buf.as_ptr());
200 pub fn linkage_to_llvm(linkage: Linkage) -> llvm::Linkage {
202 Linkage::External => llvm::Linkage::ExternalLinkage,
203 Linkage::AvailableExternally => llvm::Linkage::AvailableExternallyLinkage,
204 Linkage::LinkOnceAny => llvm::Linkage::LinkOnceAnyLinkage,
205 Linkage::LinkOnceODR => llvm::Linkage::LinkOnceODRLinkage,
206 Linkage::WeakAny => llvm::Linkage::WeakAnyLinkage,
207 Linkage::WeakODR => llvm::Linkage::WeakODRLinkage,
208 Linkage::Appending => llvm::Linkage::AppendingLinkage,
209 Linkage::Internal => llvm::Linkage::InternalLinkage,
210 Linkage::Private => llvm::Linkage::PrivateLinkage,
211 Linkage::ExternalWeak => llvm::Linkage::ExternalWeakLinkage,
212 Linkage::Common => llvm::Linkage::CommonLinkage,
216 pub fn visibility_to_llvm(linkage: Visibility) -> llvm::Visibility {
218 Visibility::Default => llvm::Visibility::Default,
219 Visibility::Hidden => llvm::Visibility::Hidden,
220 Visibility::Protected => llvm::Visibility::Protected,