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`]: crate::common::val_ty
14 use super::ModuleLlvm;
16 use crate::attributes;
17 use crate::builder::Builder;
18 use crate::context::CodegenCx;
20 use crate::value::Value;
22 use rustc_codegen_ssa::base::maybe_create_entry_wrapper;
23 use rustc_codegen_ssa::mono_item::MonoItemExt;
24 use rustc_codegen_ssa::traits::*;
25 use rustc_codegen_ssa::{ModuleCodegen, ModuleKind};
26 use rustc_data_structures::small_c_str::SmallCStr;
27 use rustc_middle::dep_graph;
28 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
29 use rustc_middle::mir::mono::{Linkage, Visibility};
30 use rustc_middle::ty::TyCtxt;
31 use rustc_session::config::DebugInfo;
32 use rustc_span::symbol::Symbol;
33 use rustc_target::spec::SanitizerSet;
35 use std::time::Instant;
37 pub struct ValueIter<'ll> {
38 cur: Option<&'ll Value>,
39 step: unsafe extern "C" fn(&'ll Value) -> Option<&'ll Value>,
42 impl<'ll> Iterator for ValueIter<'ll> {
43 type Item = &'ll Value;
45 fn next(&mut self) -> Option<&'ll Value> {
47 if let Some(old) = old {
48 self.cur = unsafe { (self.step)(old) };
54 pub fn iter_globals(llmod: &llvm::Module) -> ValueIter<'_> {
55 unsafe { ValueIter { cur: llvm::LLVMGetFirstGlobal(llmod), step: llvm::LLVMGetNextGlobal } }
58 pub fn compile_codegen_unit(tcx: TyCtxt<'_>, cgu_name: Symbol) -> (ModuleCodegen<ModuleLlvm>, u64) {
59 let start_time = Instant::now();
61 let dep_node = tcx.codegen_unit(cgu_name).codegen_dep_node(tcx);
62 let (module, _) = tcx.dep_graph.with_task(
67 Some(dep_graph::hash_result),
69 let time_to_codegen = start_time.elapsed();
71 // We assume that the cost to run LLVM on a CGU is proportional to
72 // the time we needed for codegenning it.
73 let cost = time_to_codegen.as_nanos() as u64;
75 fn module_codegen(tcx: TyCtxt<'_>, cgu_name: Symbol) -> ModuleCodegen<ModuleLlvm> {
76 let cgu = tcx.codegen_unit(cgu_name);
77 let _prof_timer = tcx.prof.generic_activity_with_args(
79 &[cgu_name.to_string(), cgu.size_estimate().to_string()],
81 // Instantiate monomorphizations without filling out definitions yet...
82 let llvm_module = ModuleLlvm::new(tcx, cgu_name.as_str());
84 let cx = CodegenCx::new(tcx, cgu, &llvm_module);
85 let mono_items = cx.codegen_unit.items_in_deterministic_order(cx.tcx);
86 for &(mono_item, (linkage, visibility)) in &mono_items {
87 mono_item.predefine::<Builder<'_, '_, '_>>(&cx, linkage, visibility);
90 // ... and now that we have everything pre-defined, fill out those definitions.
91 for &(mono_item, _) in &mono_items {
92 mono_item.define::<Builder<'_, '_, '_>>(&cx);
95 // If this codegen unit contains the main function, also create the
97 if let Some(entry) = maybe_create_entry_wrapper::<Builder<'_, '_, '_>>(&cx) {
98 let attrs = attributes::sanitize_attrs(&cx, SanitizerSet::empty());
99 attributes::apply_to_llfn(entry, llvm::AttributePlace::Function, &attrs);
102 // Finalize code coverage by injecting the coverage map. Note, the coverage map will
103 // also be added to the `llvm.compiler.used` variable, created next.
104 if cx.sess().instrument_coverage() {
105 cx.coverageinfo_finalize();
108 // Create the llvm.used and llvm.compiler.used variables.
109 if !cx.used_statics().borrow().is_empty() {
110 cx.create_used_variable()
112 if !cx.compiler_used_statics().borrow().is_empty() {
113 cx.create_compiler_used_variable()
116 // Run replace-all-uses-with for statics that need it. This must
117 // happen after the llvm.used variables are created.
118 for &(old_g, new_g) in cx.statics_to_rauw().borrow().iter() {
120 let bitcast = llvm::LLVMConstPointerCast(new_g, cx.val_ty(old_g));
121 llvm::LLVMReplaceAllUsesWith(old_g, bitcast);
122 llvm::LLVMDeleteGlobal(old_g);
126 // Finalize debuginfo
127 if cx.sess().opts.debuginfo != DebugInfo::None {
128 cx.debuginfo_finalize();
133 name: cgu_name.to_string(),
134 module_llvm: llvm_module,
135 kind: ModuleKind::Regular,
142 pub fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
143 let Some(sect) = attrs.link_section else { return };
145 let buf = SmallCStr::new(sect.as_str());
146 llvm::LLVMSetSection(llval, buf.as_ptr());
150 pub fn linkage_to_llvm(linkage: Linkage) -> llvm::Linkage {
152 Linkage::External => llvm::Linkage::ExternalLinkage,
153 Linkage::AvailableExternally => llvm::Linkage::AvailableExternallyLinkage,
154 Linkage::LinkOnceAny => llvm::Linkage::LinkOnceAnyLinkage,
155 Linkage::LinkOnceODR => llvm::Linkage::LinkOnceODRLinkage,
156 Linkage::WeakAny => llvm::Linkage::WeakAnyLinkage,
157 Linkage::WeakODR => llvm::Linkage::WeakODRLinkage,
158 Linkage::Appending => llvm::Linkage::AppendingLinkage,
159 Linkage::Internal => llvm::Linkage::InternalLinkage,
160 Linkage::Private => llvm::Linkage::PrivateLinkage,
161 Linkage::ExternalWeak => llvm::Linkage::ExternalWeakLinkage,
162 Linkage::Common => llvm::Linkage::CommonLinkage,
166 pub fn visibility_to_llvm(linkage: Visibility) -> llvm::Visibility {
168 Visibility::Default => llvm::Visibility::Default,
169 Visibility::Hidden => llvm::Visibility::Hidden,
170 Visibility::Protected => llvm::Visibility::Protected,