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223 lines
8.3 KiB
Rust
223 lines
8.3 KiB
Rust
//! Codegen the MIR to the LLVM IR.
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//!
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//! Hopefully useful general knowledge about codegen:
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//!
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//! * There's no way to find out the [`Ty`] type of a [`Value`]. Doing so
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//! would be "trying to get the eggs out of an omelette" (credit:
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//! pcwalton). You can, instead, find out its [`llvm::Type`] by calling [`val_ty`],
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//! but one [`llvm::Type`] corresponds to many [`Ty`]s; for instance, `tup(int, int,
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//! int)` and `rec(x=int, y=int, z=int)` will have the same [`llvm::Type`].
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//!
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//! [`Ty`]: rustc_middle::ty::Ty
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//! [`val_ty`]: common::val_ty
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use super::ModuleLlvm;
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use crate::attributes;
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use crate::builder::Builder;
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use crate::common;
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use crate::context::CodegenCx;
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use crate::llvm;
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use crate::value::Value;
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use rustc_codegen_ssa::base::maybe_create_entry_wrapper;
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use rustc_codegen_ssa::mono_item::MonoItemExt;
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use rustc_codegen_ssa::traits::*;
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use rustc_codegen_ssa::{ModuleCodegen, ModuleKind};
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use rustc_data_structures::small_c_str::SmallCStr;
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use rustc_metadata::EncodedMetadata;
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use rustc_middle::dep_graph;
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use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
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use rustc_middle::middle::exported_symbols;
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use rustc_middle::mir::mono::{Linkage, Visibility};
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use rustc_middle::ty::TyCtxt;
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use rustc_session::config::DebugInfo;
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use rustc_span::symbol::Symbol;
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use rustc_target::spec::SanitizerSet;
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use std::ffi::CString;
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use std::time::Instant;
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pub fn write_compressed_metadata<'tcx>(
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tcx: TyCtxt<'tcx>,
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metadata: &EncodedMetadata,
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llvm_module: &mut ModuleLlvm,
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) {
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use snap::write::FrameEncoder;
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use std::io::Write;
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// Historical note:
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//
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// When using link.exe it was seen that the section name `.note.rustc`
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// was getting shortened to `.note.ru`, and according to the PE and COFF
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// specification:
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//
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// > Executable images do not use a string table and do not support
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// > section names longer than 8 characters
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//
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// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format
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//
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// As a result, we choose a slightly shorter name! As to why
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// `.note.rustc` works on MinGW, see
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// https://github.com/llvm/llvm-project/blob/llvmorg-12.0.0/lld/COFF/Writer.cpp#L1190-L1197
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let section_name = if tcx.sess.target.is_like_osx { "__DATA,.rustc" } else { ".rustc" };
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let (metadata_llcx, metadata_llmod) = (&*llvm_module.llcx, llvm_module.llmod());
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let mut compressed = rustc_metadata::METADATA_HEADER.to_vec();
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FrameEncoder::new(&mut compressed).write_all(metadata.raw_data()).unwrap();
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let llmeta = common::bytes_in_context(metadata_llcx, &compressed);
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let llconst = common::struct_in_context(metadata_llcx, &[llmeta], false);
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let name = exported_symbols::metadata_symbol_name(tcx);
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let buf = CString::new(name).unwrap();
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let llglobal =
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unsafe { llvm::LLVMAddGlobal(metadata_llmod, common::val_ty(llconst), buf.as_ptr()) };
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unsafe {
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llvm::LLVMSetInitializer(llglobal, llconst);
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let name = SmallCStr::new(section_name);
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llvm::LLVMSetSection(llglobal, name.as_ptr());
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// Also generate a .section directive to force no
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// flags, at least for ELF outputs, so that the
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// metadata doesn't get loaded into memory.
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let directive = format!(".section {}", section_name);
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llvm::LLVMSetModuleInlineAsm2(metadata_llmod, directive.as_ptr().cast(), directive.len())
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}
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}
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pub struct ValueIter<'ll> {
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cur: Option<&'ll Value>,
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step: unsafe extern "C" fn(&'ll Value) -> Option<&'ll Value>,
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}
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impl Iterator for ValueIter<'ll> {
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type Item = &'ll Value;
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fn next(&mut self) -> Option<&'ll Value> {
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let old = self.cur;
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if let Some(old) = old {
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self.cur = unsafe { (self.step)(old) };
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}
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old
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}
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}
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pub fn iter_globals(llmod: &'ll llvm::Module) -> ValueIter<'ll> {
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unsafe { ValueIter { cur: llvm::LLVMGetFirstGlobal(llmod), step: llvm::LLVMGetNextGlobal } }
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}
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pub fn compile_codegen_unit(
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tcx: TyCtxt<'tcx>,
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cgu_name: Symbol,
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) -> (ModuleCodegen<ModuleLlvm>, u64) {
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let start_time = Instant::now();
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let dep_node = tcx.codegen_unit(cgu_name).codegen_dep_node(tcx);
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let (module, _) =
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tcx.dep_graph.with_task(dep_node, tcx, cgu_name, module_codegen, dep_graph::hash_result);
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let time_to_codegen = start_time.elapsed();
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// We assume that the cost to run LLVM on a CGU is proportional to
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// the time we needed for codegenning it.
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let cost = time_to_codegen.as_nanos() as u64;
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fn module_codegen(tcx: TyCtxt<'_>, cgu_name: Symbol) -> ModuleCodegen<ModuleLlvm> {
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let cgu = tcx.codegen_unit(cgu_name);
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let _prof_timer = tcx.prof.generic_activity_with_args(
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"codegen_module",
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&[cgu_name.to_string(), cgu.size_estimate().to_string()],
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);
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// Instantiate monomorphizations without filling out definitions yet...
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let llvm_module = ModuleLlvm::new(tcx, &cgu_name.as_str());
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{
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let cx = CodegenCx::new(tcx, cgu, &llvm_module);
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let mono_items = cx.codegen_unit.items_in_deterministic_order(cx.tcx);
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for &(mono_item, (linkage, visibility)) in &mono_items {
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mono_item.predefine::<Builder<'_, '_, '_>>(&cx, linkage, visibility);
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}
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// ... and now that we have everything pre-defined, fill out those definitions.
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for &(mono_item, _) in &mono_items {
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mono_item.define::<Builder<'_, '_, '_>>(&cx);
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}
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// If this codegen unit contains the main function, also create the
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// wrapper here
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if let Some(entry) = maybe_create_entry_wrapper::<Builder<'_, '_, '_>>(&cx) {
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attributes::sanitize(&cx, SanitizerSet::empty(), entry);
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}
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// Run replace-all-uses-with for statics that need it
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for &(old_g, new_g) in cx.statics_to_rauw().borrow().iter() {
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unsafe {
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let bitcast = llvm::LLVMConstPointerCast(new_g, cx.val_ty(old_g));
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llvm::LLVMReplaceAllUsesWith(old_g, bitcast);
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llvm::LLVMDeleteGlobal(old_g);
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}
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}
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// Finalize code coverage by injecting the coverage map. Note, the coverage map will
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// also be added to the `llvm.compiler.used` variable, created next.
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if cx.sess().instrument_coverage() {
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cx.coverageinfo_finalize();
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}
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// Create the llvm.used and llvm.compiler.used variables.
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if !cx.used_statics().borrow().is_empty() {
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cx.create_used_variable()
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}
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if !cx.compiler_used_statics().borrow().is_empty() {
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cx.create_compiler_used_variable()
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}
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// Finalize debuginfo
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if cx.sess().opts.debuginfo != DebugInfo::None {
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cx.debuginfo_finalize();
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}
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}
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ModuleCodegen {
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name: cgu_name.to_string(),
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module_llvm: llvm_module,
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kind: ModuleKind::Regular,
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}
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}
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(module, cost)
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}
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pub fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
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let sect = match attrs.link_section {
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Some(name) => name,
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None => return,
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};
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unsafe {
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let buf = SmallCStr::new(§.as_str());
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llvm::LLVMSetSection(llval, buf.as_ptr());
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}
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}
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pub fn linkage_to_llvm(linkage: Linkage) -> llvm::Linkage {
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match linkage {
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Linkage::External => llvm::Linkage::ExternalLinkage,
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Linkage::AvailableExternally => llvm::Linkage::AvailableExternallyLinkage,
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Linkage::LinkOnceAny => llvm::Linkage::LinkOnceAnyLinkage,
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Linkage::LinkOnceODR => llvm::Linkage::LinkOnceODRLinkage,
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Linkage::WeakAny => llvm::Linkage::WeakAnyLinkage,
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Linkage::WeakODR => llvm::Linkage::WeakODRLinkage,
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Linkage::Appending => llvm::Linkage::AppendingLinkage,
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Linkage::Internal => llvm::Linkage::InternalLinkage,
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Linkage::Private => llvm::Linkage::PrivateLinkage,
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Linkage::ExternalWeak => llvm::Linkage::ExternalWeakLinkage,
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Linkage::Common => llvm::Linkage::CommonLinkage,
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}
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}
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pub fn visibility_to_llvm(linkage: Visibility) -> llvm::Visibility {
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match linkage {
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Visibility::Default => llvm::Visibility::Default,
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Visibility::Hidden => llvm::Visibility::Hidden,
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Visibility::Protected => llvm::Visibility::Protected,
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}
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}
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