| use crate::back::bytecode::DecodedBytecode; |
| use crate::back::write::{self, DiagnosticHandlers, with_llvm_pmb, save_temp_bitcode, |
| to_llvm_opt_settings}; |
| use crate::llvm::archive_ro::ArchiveRO; |
| use crate::llvm::{self, True, False}; |
| use crate::{ModuleLlvm, LlvmCodegenBackend}; |
| use rustc_codegen_ssa::back::symbol_export; |
| use rustc_codegen_ssa::back::write::{ModuleConfig, CodegenContext, FatLTOInput}; |
| use rustc_codegen_ssa::back::lto::{SerializedModule, LtoModuleCodegen, ThinShared, ThinModule}; |
| use rustc_codegen_ssa::traits::*; |
| use errors::{FatalError, Handler}; |
| use rustc::dep_graph::WorkProduct; |
| use rustc::dep_graph::cgu_reuse_tracker::CguReuse; |
| use rustc::hir::def_id::LOCAL_CRATE; |
| use rustc::middle::exported_symbols::SymbolExportLevel; |
| use rustc::session::config::{self, Lto}; |
| use rustc::util::common::time_ext; |
| use rustc_data_structures::fx::FxHashMap; |
| use rustc_codegen_ssa::{RLIB_BYTECODE_EXTENSION, ModuleCodegen, ModuleKind}; |
| |
| use std::ffi::{CStr, CString}; |
| use std::ptr; |
| use std::slice; |
| use std::sync::Arc; |
| |
| pub fn crate_type_allows_lto(crate_type: config::CrateType) -> bool { |
| match crate_type { |
| config::CrateType::Executable | |
| config::CrateType::Staticlib | |
| config::CrateType::Cdylib => true, |
| |
| config::CrateType::Dylib | |
| config::CrateType::Rlib | |
| config::CrateType::ProcMacro => false, |
| } |
| } |
| |
| fn prepare_lto(cgcx: &CodegenContext<LlvmCodegenBackend>, |
| diag_handler: &Handler) |
| -> Result<(Vec<CString>, Vec<(SerializedModule<ModuleBuffer>, CString)>), FatalError> |
| { |
| let export_threshold = match cgcx.lto { |
| // We're just doing LTO for our one crate |
| Lto::ThinLocal => SymbolExportLevel::Rust, |
| |
| // We're doing LTO for the entire crate graph |
| Lto::Fat | Lto::Thin => { |
| symbol_export::crates_export_threshold(&cgcx.crate_types) |
| } |
| |
| Lto::No => panic!("didn't request LTO but we're doing LTO"), |
| }; |
| |
| let symbol_filter = &|&(ref name, level): &(String, SymbolExportLevel)| { |
| if level.is_below_threshold(export_threshold) { |
| Some(CString::new(name.as_str()).unwrap()) |
| } else { |
| None |
| } |
| }; |
| let exported_symbols = cgcx.exported_symbols |
| .as_ref().expect("needs exported symbols for LTO"); |
| let mut symbol_white_list = { |
| let _timer = cgcx.prof.generic_activity("LLVM_lto_generate_symbol_white_list"); |
| exported_symbols[&LOCAL_CRATE] |
| .iter() |
| .filter_map(symbol_filter) |
| .collect::<Vec<CString>>() |
| }; |
| info!("{} symbols to preserve in this crate", symbol_white_list.len()); |
| |
| // If we're performing LTO for the entire crate graph, then for each of our |
| // upstream dependencies, find the corresponding rlib and load the bitcode |
| // from the archive. |
| // |
| // We save off all the bytecode and LLVM module ids for later processing |
| // with either fat or thin LTO |
| let mut upstream_modules = Vec::new(); |
| if cgcx.lto != Lto::ThinLocal { |
| if cgcx.opts.cg.prefer_dynamic { |
| diag_handler.struct_err("cannot prefer dynamic linking when performing LTO") |
| .note("only 'staticlib', 'bin', and 'cdylib' outputs are \ |
| supported with LTO") |
| .emit(); |
| return Err(FatalError) |
| } |
| |
| // Make sure we actually can run LTO |
| for crate_type in cgcx.crate_types.iter() { |
| if !crate_type_allows_lto(*crate_type) { |
| let e = diag_handler.fatal("lto can only be run for executables, cdylibs and \ |
| static library outputs"); |
| return Err(e) |
| } |
| } |
| |
| for &(cnum, ref path) in cgcx.each_linked_rlib_for_lto.iter() { |
| let exported_symbols = cgcx.exported_symbols |
| .as_ref().expect("needs exported symbols for LTO"); |
| { |
| let _timer = cgcx.prof.generic_activity("LLVM_lto_generate_symbol_white_list"); |
| symbol_white_list.extend( |
| exported_symbols[&cnum] |
| .iter() |
| .filter_map(symbol_filter)); |
| } |
| |
| let _timer = cgcx.prof.generic_activity("LLVM_lto_load_upstream_bitcode"); |
| let archive = ArchiveRO::open(&path).expect("wanted an rlib"); |
| let bytecodes = archive.iter().filter_map(|child| { |
| child.ok().and_then(|c| c.name().map(|name| (name, c))) |
| }).filter(|&(name, _)| name.ends_with(RLIB_BYTECODE_EXTENSION)); |
| for (name, data) in bytecodes { |
| info!("adding bytecode {}", name); |
| let bc_encoded = data.data(); |
| |
| let (bc, id) = time_ext(cgcx.time_passes, &format!("decode {}", name), || { |
| match DecodedBytecode::new(bc_encoded) { |
| Ok(b) => Ok((b.bytecode(), b.identifier().to_string())), |
| Err(e) => Err(diag_handler.fatal(&e)), |
| } |
| })?; |
| let bc = SerializedModule::FromRlib(bc); |
| upstream_modules.push((bc, CString::new(id).unwrap())); |
| } |
| } |
| } |
| |
| Ok((symbol_white_list, upstream_modules)) |
| } |
| |
| /// Performs fat LTO by merging all modules into a single one and returning it |
| /// for further optimization. |
| pub(crate) fn run_fat(cgcx: &CodegenContext<LlvmCodegenBackend>, |
| modules: Vec<FatLTOInput<LlvmCodegenBackend>>, |
| cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>) |
| -> Result<LtoModuleCodegen<LlvmCodegenBackend>, FatalError> |
| { |
| let diag_handler = cgcx.create_diag_handler(); |
| let (symbol_white_list, upstream_modules) = prepare_lto(cgcx, &diag_handler)?; |
| let symbol_white_list = symbol_white_list.iter() |
| .map(|c| c.as_ptr()) |
| .collect::<Vec<_>>(); |
| fat_lto( |
| cgcx, |
| &diag_handler, |
| modules, |
| cached_modules, |
| upstream_modules, |
| &symbol_white_list, |
| ) |
| } |
| |
| /// Performs thin LTO by performing necessary global analysis and returning two |
| /// lists, one of the modules that need optimization and another for modules that |
| /// can simply be copied over from the incr. comp. cache. |
| pub(crate) fn run_thin(cgcx: &CodegenContext<LlvmCodegenBackend>, |
| modules: Vec<(String, ThinBuffer)>, |
| cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>) |
| -> Result<(Vec<LtoModuleCodegen<LlvmCodegenBackend>>, Vec<WorkProduct>), FatalError> |
| { |
| let diag_handler = cgcx.create_diag_handler(); |
| let (symbol_white_list, upstream_modules) = prepare_lto(cgcx, &diag_handler)?; |
| let symbol_white_list = symbol_white_list.iter() |
| .map(|c| c.as_ptr()) |
| .collect::<Vec<_>>(); |
| if cgcx.opts.cg.linker_plugin_lto.enabled() { |
| unreachable!("We should never reach this case if the LTO step \ |
| is deferred to the linker"); |
| } |
| thin_lto(cgcx, |
| &diag_handler, |
| modules, |
| upstream_modules, |
| cached_modules, |
| &symbol_white_list) |
| } |
| |
| pub(crate) fn prepare_thin( |
| module: ModuleCodegen<ModuleLlvm> |
| ) -> (String, ThinBuffer) { |
| let name = module.name.clone(); |
| let buffer = ThinBuffer::new(module.module_llvm.llmod()); |
| (name, buffer) |
| } |
| |
| fn fat_lto(cgcx: &CodegenContext<LlvmCodegenBackend>, |
| diag_handler: &Handler, |
| modules: Vec<FatLTOInput<LlvmCodegenBackend>>, |
| cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>, |
| mut serialized_modules: Vec<(SerializedModule<ModuleBuffer>, CString)>, |
| symbol_white_list: &[*const libc::c_char]) |
| -> Result<LtoModuleCodegen<LlvmCodegenBackend>, FatalError> |
| { |
| let _timer = cgcx.prof.generic_activity("LLVM_fat_lto_build_monolithic_module"); |
| info!("going for a fat lto"); |
| |
| // Sort out all our lists of incoming modules into two lists. |
| // |
| // * `serialized_modules` (also and argument to this function) contains all |
| // modules that are serialized in-memory. |
| // * `in_memory` contains modules which are already parsed and in-memory, |
| // such as from multi-CGU builds. |
| // |
| // All of `cached_modules` (cached from previous incremental builds) can |
| // immediately go onto the `serialized_modules` modules list and then we can |
| // split the `modules` array into these two lists. |
| let mut in_memory = Vec::new(); |
| serialized_modules.extend(cached_modules.into_iter().map(|(buffer, wp)| { |
| info!("pushing cached module {:?}", wp.cgu_name); |
| (buffer, CString::new(wp.cgu_name).unwrap()) |
| })); |
| for module in modules { |
| match module { |
| FatLTOInput::InMemory(m) => in_memory.push(m), |
| FatLTOInput::Serialized { name, buffer } => { |
| info!("pushing serialized module {:?}", name); |
| let buffer = SerializedModule::Local(buffer); |
| serialized_modules.push((buffer, CString::new(name).unwrap())); |
| } |
| } |
| } |
| |
| // Find the "costliest" module and merge everything into that codegen unit. |
| // All the other modules will be serialized and reparsed into the new |
| // context, so this hopefully avoids serializing and parsing the largest |
| // codegen unit. |
| // |
| // Additionally use a regular module as the base here to ensure that various |
| // file copy operations in the backend work correctly. The only other kind |
| // of module here should be an allocator one, and if your crate is smaller |
| // than the allocator module then the size doesn't really matter anyway. |
| let costliest_module = in_memory.iter() |
| .enumerate() |
| .filter(|&(_, module)| module.kind == ModuleKind::Regular) |
| .map(|(i, module)| { |
| let cost = unsafe { |
| llvm::LLVMRustModuleCost(module.module_llvm.llmod()) |
| }; |
| (cost, i) |
| }) |
| .max(); |
| |
| // If we found a costliest module, we're good to go. Otherwise all our |
| // inputs were serialized which could happen in the case, for example, that |
| // all our inputs were incrementally reread from the cache and we're just |
| // re-executing the LTO passes. If that's the case deserialize the first |
| // module and create a linker with it. |
| let module: ModuleCodegen<ModuleLlvm> = match costliest_module { |
| Some((_cost, i)) => in_memory.remove(i), |
| None => { |
| assert!(serialized_modules.len() > 0, "must have at least one serialized module"); |
| let (buffer, name) = serialized_modules.remove(0); |
| info!("no in-memory regular modules to choose from, parsing {:?}", name); |
| ModuleCodegen { |
| module_llvm: ModuleLlvm::parse(cgcx, &name, buffer.data(), diag_handler)?, |
| name: name.into_string().unwrap(), |
| kind: ModuleKind::Regular, |
| } |
| } |
| }; |
| let mut serialized_bitcode = Vec::new(); |
| { |
| let (llcx, llmod) = { |
| let llvm = &module.module_llvm; |
| (&llvm.llcx, llvm.llmod()) |
| }; |
| info!("using {:?} as a base module", module.name); |
| |
| // The linking steps below may produce errors and diagnostics within LLVM |
| // which we'd like to handle and print, so set up our diagnostic handlers |
| // (which get unregistered when they go out of scope below). |
| let _handler = DiagnosticHandlers::new(cgcx, diag_handler, llcx); |
| |
| // For all other modules we codegened we'll need to link them into our own |
| // bitcode. All modules were codegened in their own LLVM context, however, |
| // and we want to move everything to the same LLVM context. Currently the |
| // way we know of to do that is to serialize them to a string and them parse |
| // them later. Not great but hey, that's why it's "fat" LTO, right? |
| for module in in_memory { |
| let buffer = ModuleBuffer::new(module.module_llvm.llmod()); |
| let llmod_id = CString::new(&module.name[..]).unwrap(); |
| serialized_modules.push((SerializedModule::Local(buffer), llmod_id)); |
| } |
| // Sort the modules to ensure we produce deterministic results. |
| serialized_modules.sort_by(|module1, module2| module1.1.cmp(&module2.1)); |
| |
| // For all serialized bitcode files we parse them and link them in as we did |
| // above, this is all mostly handled in C++. Like above, though, we don't |
| // know much about the memory management here so we err on the side of being |
| // save and persist everything with the original module. |
| let mut linker = Linker::new(llmod); |
| for (bc_decoded, name) in serialized_modules { |
| let _timer = cgcx.prof.generic_activity("LLVM_fat_lto_link_module"); |
| info!("linking {:?}", name); |
| time_ext(cgcx.time_passes, &format!("ll link {:?}", name), || { |
| let data = bc_decoded.data(); |
| linker.add(&data).map_err(|()| { |
| let msg = format!("failed to load bc of {:?}", name); |
| write::llvm_err(&diag_handler, &msg) |
| }) |
| })?; |
| serialized_bitcode.push(bc_decoded); |
| } |
| drop(linker); |
| save_temp_bitcode(&cgcx, &module, "lto.input"); |
| |
| // Internalize everything that *isn't* in our whitelist to help strip out |
| // more modules and such |
| unsafe { |
| let ptr = symbol_white_list.as_ptr(); |
| llvm::LLVMRustRunRestrictionPass(llmod, |
| ptr as *const *const libc::c_char, |
| symbol_white_list.len() as libc::size_t); |
| save_temp_bitcode(&cgcx, &module, "lto.after-restriction"); |
| } |
| |
| if cgcx.no_landing_pads { |
| unsafe { |
| llvm::LLVMRustMarkAllFunctionsNounwind(llmod); |
| } |
| save_temp_bitcode(&cgcx, &module, "lto.after-nounwind"); |
| } |
| } |
| |
| Ok(LtoModuleCodegen::Fat { |
| module: Some(module), |
| _serialized_bitcode: serialized_bitcode, |
| }) |
| } |
| |
| struct Linker<'a>(&'a mut llvm::Linker<'a>); |
| |
| impl Linker<'a> { |
| fn new(llmod: &'a llvm::Module) -> Self { |
| unsafe { Linker(llvm::LLVMRustLinkerNew(llmod)) } |
| } |
| |
| fn add(&mut self, bytecode: &[u8]) -> Result<(), ()> { |
| unsafe { |
| if llvm::LLVMRustLinkerAdd(self.0, |
| bytecode.as_ptr() as *const libc::c_char, |
| bytecode.len()) { |
| Ok(()) |
| } else { |
| Err(()) |
| } |
| } |
| } |
| } |
| |
| impl Drop for Linker<'a> { |
| fn drop(&mut self) { |
| unsafe { llvm::LLVMRustLinkerFree(&mut *(self.0 as *mut _)); } |
| } |
| } |
| |
| /// Prepare "thin" LTO to get run on these modules. |
| /// |
| /// The general structure of ThinLTO is quite different from the structure of |
| /// "fat" LTO above. With "fat" LTO all LLVM modules in question are merged into |
| /// one giant LLVM module, and then we run more optimization passes over this |
| /// big module after internalizing most symbols. Thin LTO, on the other hand, |
| /// avoid this large bottleneck through more targeted optimization. |
| /// |
| /// At a high level Thin LTO looks like: |
| /// |
| /// 1. Prepare a "summary" of each LLVM module in question which describes |
| /// the values inside, cost of the values, etc. |
| /// 2. Merge the summaries of all modules in question into one "index" |
| /// 3. Perform some global analysis on this index |
| /// 4. For each module, use the index and analysis calculated previously to |
| /// perform local transformations on the module, for example inlining |
| /// small functions from other modules. |
| /// 5. Run thin-specific optimization passes over each module, and then code |
| /// generate everything at the end. |
| /// |
| /// The summary for each module is intended to be quite cheap, and the global |
| /// index is relatively quite cheap to create as well. As a result, the goal of |
| /// ThinLTO is to reduce the bottleneck on LTO and enable LTO to be used in more |
| /// situations. For example one cheap optimization is that we can parallelize |
| /// all codegen modules, easily making use of all the cores on a machine. |
| /// |
| /// With all that in mind, the function here is designed at specifically just |
| /// calculating the *index* for ThinLTO. This index will then be shared amongst |
| /// all of the `LtoModuleCodegen` units returned below and destroyed once |
| /// they all go out of scope. |
| fn thin_lto(cgcx: &CodegenContext<LlvmCodegenBackend>, |
| diag_handler: &Handler, |
| modules: Vec<(String, ThinBuffer)>, |
| serialized_modules: Vec<(SerializedModule<ModuleBuffer>, CString)>, |
| cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>, |
| symbol_white_list: &[*const libc::c_char]) |
| -> Result<(Vec<LtoModuleCodegen<LlvmCodegenBackend>>, Vec<WorkProduct>), FatalError> |
| { |
| let _timer = cgcx.prof.generic_activity("LLVM_thin_lto_global_analysis"); |
| unsafe { |
| info!("going for that thin, thin LTO"); |
| |
| let green_modules: FxHashMap<_, _> = cached_modules |
| .iter() |
| .map(|&(_, ref wp)| (wp.cgu_name.clone(), wp.clone())) |
| .collect(); |
| |
| let full_scope_len = modules.len() + serialized_modules.len() + cached_modules.len(); |
| let mut thin_buffers = Vec::with_capacity(modules.len()); |
| let mut module_names = Vec::with_capacity(full_scope_len); |
| let mut thin_modules = Vec::with_capacity(full_scope_len); |
| |
| for (i, (name, buffer)) in modules.into_iter().enumerate() { |
| info!("local module: {} - {}", i, name); |
| let cname = CString::new(name.clone()).unwrap(); |
| thin_modules.push(llvm::ThinLTOModule { |
| identifier: cname.as_ptr(), |
| data: buffer.data().as_ptr(), |
| len: buffer.data().len(), |
| }); |
| thin_buffers.push(buffer); |
| module_names.push(cname); |
| } |
| |
| // FIXME: All upstream crates are deserialized internally in the |
| // function below to extract their summary and modules. Note that |
| // unlike the loop above we *must* decode and/or read something |
| // here as these are all just serialized files on disk. An |
| // improvement, however, to make here would be to store the |
| // module summary separately from the actual module itself. Right |
| // now this is store in one large bitcode file, and the entire |
| // file is deflate-compressed. We could try to bypass some of the |
| // decompression by storing the index uncompressed and only |
| // lazily decompressing the bytecode if necessary. |
| // |
| // Note that truly taking advantage of this optimization will |
| // likely be further down the road. We'd have to implement |
| // incremental ThinLTO first where we could actually avoid |
| // looking at upstream modules entirely sometimes (the contents, |
| // we must always unconditionally look at the index). |
| let mut serialized = Vec::with_capacity(serialized_modules.len() + cached_modules.len()); |
| |
| let cached_modules = cached_modules.into_iter().map(|(sm, wp)| { |
| (sm, CString::new(wp.cgu_name).unwrap()) |
| }); |
| |
| for (module, name) in serialized_modules.into_iter().chain(cached_modules) { |
| info!("upstream or cached module {:?}", name); |
| thin_modules.push(llvm::ThinLTOModule { |
| identifier: name.as_ptr(), |
| data: module.data().as_ptr(), |
| len: module.data().len(), |
| }); |
| serialized.push(module); |
| module_names.push(name); |
| } |
| |
| // Sanity check |
| assert_eq!(thin_modules.len(), module_names.len()); |
| |
| // Delegate to the C++ bindings to create some data here. Once this is a |
| // tried-and-true interface we may wish to try to upstream some of this |
| // to LLVM itself, right now we reimplement a lot of what they do |
| // upstream... |
| let data = llvm::LLVMRustCreateThinLTOData( |
| thin_modules.as_ptr(), |
| thin_modules.len() as u32, |
| symbol_white_list.as_ptr(), |
| symbol_white_list.len() as u32, |
| ).ok_or_else(|| { |
| write::llvm_err(&diag_handler, "failed to prepare thin LTO context") |
| })?; |
| |
| info!("thin LTO data created"); |
| |
| let import_map = if cgcx.incr_comp_session_dir.is_some() { |
| ThinLTOImports::from_thin_lto_data(data) |
| } else { |
| // If we don't compile incrementally, we don't need to load the |
| // import data from LLVM. |
| assert!(green_modules.is_empty()); |
| ThinLTOImports::default() |
| }; |
| info!("thin LTO import map loaded"); |
| |
| let data = ThinData(data); |
| |
| // Throw our data in an `Arc` as we'll be sharing it across threads. We |
| // also put all memory referenced by the C++ data (buffers, ids, etc) |
| // into the arc as well. After this we'll create a thin module |
| // codegen per module in this data. |
| let shared = Arc::new(ThinShared { |
| data, |
| thin_buffers, |
| serialized_modules: serialized, |
| module_names, |
| }); |
| |
| let mut copy_jobs = vec![]; |
| let mut opt_jobs = vec![]; |
| |
| info!("checking which modules can be-reused and which have to be re-optimized."); |
| for (module_index, module_name) in shared.module_names.iter().enumerate() { |
| let module_name = module_name_to_str(module_name); |
| |
| // If the module hasn't changed and none of the modules it imports |
| // from has changed, we can re-use the post-ThinLTO version of the |
| // module. |
| if green_modules.contains_key(module_name) { |
| let imports_all_green = import_map.modules_imported_by(module_name) |
| .iter() |
| .all(|imported_module| green_modules.contains_key(imported_module)); |
| |
| if imports_all_green { |
| let work_product = green_modules[module_name].clone(); |
| copy_jobs.push(work_product); |
| info!(" - {}: re-used", module_name); |
| cgcx.cgu_reuse_tracker.set_actual_reuse(module_name, |
| CguReuse::PostLto); |
| continue |
| } |
| } |
| |
| info!(" - {}: re-compiled", module_name); |
| opt_jobs.push(LtoModuleCodegen::Thin(ThinModule { |
| shared: shared.clone(), |
| idx: module_index, |
| })); |
| } |
| |
| Ok((opt_jobs, copy_jobs)) |
| } |
| } |
| |
| pub(crate) fn run_pass_manager(cgcx: &CodegenContext<LlvmCodegenBackend>, |
| module: &ModuleCodegen<ModuleLlvm>, |
| config: &ModuleConfig, |
| thin: bool) { |
| // Now we have one massive module inside of llmod. Time to run the |
| // LTO-specific optimization passes that LLVM provides. |
| // |
| // This code is based off the code found in llvm's LTO code generator: |
| // tools/lto/LTOCodeGenerator.cpp |
| debug!("running the pass manager"); |
| unsafe { |
| let pm = llvm::LLVMCreatePassManager(); |
| llvm::LLVMAddAnalysisPasses(module.module_llvm.tm, pm); |
| |
| if config.verify_llvm_ir { |
| let pass = llvm::LLVMRustFindAndCreatePass("verify\0".as_ptr().cast()); |
| llvm::LLVMRustAddPass(pm, pass.unwrap()); |
| } |
| |
| // When optimizing for LTO we don't actually pass in `-O0`, but we force |
| // it to always happen at least with `-O1`. |
| // |
| // With ThinLTO we mess around a lot with symbol visibility in a way |
| // that will actually cause linking failures if we optimize at O0 which |
| // notable is lacking in dead code elimination. To ensure we at least |
| // get some optimizations and correctly link we forcibly switch to `-O1` |
| // to get dead code elimination. |
| // |
| // Note that in general this shouldn't matter too much as you typically |
| // only turn on ThinLTO when you're compiling with optimizations |
| // otherwise. |
| let opt_level = config.opt_level.map(|x| to_llvm_opt_settings(x).0) |
| .unwrap_or(llvm::CodeGenOptLevel::None); |
| let opt_level = match opt_level { |
| llvm::CodeGenOptLevel::None => llvm::CodeGenOptLevel::Less, |
| level => level, |
| }; |
| with_llvm_pmb(module.module_llvm.llmod(), config, opt_level, false, &mut |b| { |
| if thin { |
| llvm::LLVMRustPassManagerBuilderPopulateThinLTOPassManager(b, pm); |
| } else { |
| llvm::LLVMPassManagerBuilderPopulateLTOPassManager(b, pm, |
| /* Internalize = */ False, |
| /* RunInliner = */ True); |
| } |
| }); |
| |
| // We always generate bitcode through ThinLTOBuffers, |
| // which do not support anonymous globals |
| if config.bitcode_needed() { |
| let pass = llvm::LLVMRustFindAndCreatePass("name-anon-globals\0".as_ptr().cast()); |
| llvm::LLVMRustAddPass(pm, pass.unwrap()); |
| } |
| |
| if config.verify_llvm_ir { |
| let pass = llvm::LLVMRustFindAndCreatePass("verify\0".as_ptr().cast()); |
| llvm::LLVMRustAddPass(pm, pass.unwrap()); |
| } |
| |
| time_ext(cgcx.time_passes, "LTO passes", || |
| llvm::LLVMRunPassManager(pm, module.module_llvm.llmod())); |
| |
| llvm::LLVMDisposePassManager(pm); |
| } |
| debug!("lto done"); |
| } |
| |
| pub struct ModuleBuffer(&'static mut llvm::ModuleBuffer); |
| |
| unsafe impl Send for ModuleBuffer {} |
| unsafe impl Sync for ModuleBuffer {} |
| |
| impl ModuleBuffer { |
| pub fn new(m: &llvm::Module) -> ModuleBuffer { |
| ModuleBuffer(unsafe { |
| llvm::LLVMRustModuleBufferCreate(m) |
| }) |
| } |
| } |
| |
| impl ModuleBufferMethods for ModuleBuffer { |
| fn data(&self) -> &[u8] { |
| unsafe { |
| let ptr = llvm::LLVMRustModuleBufferPtr(self.0); |
| let len = llvm::LLVMRustModuleBufferLen(self.0); |
| slice::from_raw_parts(ptr, len) |
| } |
| } |
| } |
| |
| impl Drop for ModuleBuffer { |
| fn drop(&mut self) { |
| unsafe { llvm::LLVMRustModuleBufferFree(&mut *(self.0 as *mut _)); } |
| } |
| } |
| |
| pub struct ThinData(&'static mut llvm::ThinLTOData); |
| |
| unsafe impl Send for ThinData {} |
| unsafe impl Sync for ThinData {} |
| |
| impl Drop for ThinData { |
| fn drop(&mut self) { |
| unsafe { |
| llvm::LLVMRustFreeThinLTOData(&mut *(self.0 as *mut _)); |
| } |
| } |
| } |
| |
| pub struct ThinBuffer(&'static mut llvm::ThinLTOBuffer); |
| |
| unsafe impl Send for ThinBuffer {} |
| unsafe impl Sync for ThinBuffer {} |
| |
| impl ThinBuffer { |
| pub fn new(m: &llvm::Module) -> ThinBuffer { |
| unsafe { |
| let buffer = llvm::LLVMRustThinLTOBufferCreate(m); |
| ThinBuffer(buffer) |
| } |
| } |
| } |
| |
| impl ThinBufferMethods for ThinBuffer { |
| fn data(&self) -> &[u8] { |
| unsafe { |
| let ptr = llvm::LLVMRustThinLTOBufferPtr(self.0) as *const _; |
| let len = llvm::LLVMRustThinLTOBufferLen(self.0); |
| slice::from_raw_parts(ptr, len) |
| } |
| } |
| } |
| |
| impl Drop for ThinBuffer { |
| fn drop(&mut self) { |
| unsafe { |
| llvm::LLVMRustThinLTOBufferFree(&mut *(self.0 as *mut _)); |
| } |
| } |
| } |
| |
| pub unsafe fn optimize_thin_module( |
| thin_module: &mut ThinModule<LlvmCodegenBackend>, |
| cgcx: &CodegenContext<LlvmCodegenBackend>, |
| ) -> Result<ModuleCodegen<ModuleLlvm>, FatalError> { |
| let diag_handler = cgcx.create_diag_handler(); |
| let tm = (cgcx.tm_factory.0)().map_err(|e| { |
| write::llvm_err(&diag_handler, &e) |
| })?; |
| |
| // Right now the implementation we've got only works over serialized |
| // modules, so we create a fresh new LLVM context and parse the module |
| // into that context. One day, however, we may do this for upstream |
| // crates but for locally codegened modules we may be able to reuse |
| // that LLVM Context and Module. |
| let llcx = llvm::LLVMRustContextCreate(cgcx.fewer_names); |
| let llmod_raw = parse_module( |
| llcx, |
| &thin_module.shared.module_names[thin_module.idx], |
| thin_module.data(), |
| &diag_handler, |
| )? as *const _; |
| let module = ModuleCodegen { |
| module_llvm: ModuleLlvm { |
| llmod_raw, |
| llcx, |
| tm, |
| }, |
| name: thin_module.name().to_string(), |
| kind: ModuleKind::Regular, |
| }; |
| { |
| let llmod = module.module_llvm.llmod(); |
| save_temp_bitcode(&cgcx, &module, "thin-lto-input"); |
| |
| // Before we do much else find the "main" `DICompileUnit` that we'll be |
| // using below. If we find more than one though then rustc has changed |
| // in a way we're not ready for, so generate an ICE by returning |
| // an error. |
| let mut cu1 = ptr::null_mut(); |
| let mut cu2 = ptr::null_mut(); |
| llvm::LLVMRustThinLTOGetDICompileUnit(llmod, &mut cu1, &mut cu2); |
| if !cu2.is_null() { |
| let msg = "multiple source DICompileUnits found"; |
| return Err(write::llvm_err(&diag_handler, msg)) |
| } |
| |
| // Like with "fat" LTO, get some better optimizations if landing pads |
| // are disabled by removing all landing pads. |
| if cgcx.no_landing_pads { |
| let _timer = cgcx.prof.generic_activity("LLVM_thin_lto_remove_landing_pads"); |
| llvm::LLVMRustMarkAllFunctionsNounwind(llmod); |
| save_temp_bitcode(&cgcx, &module, "thin-lto-after-nounwind"); |
| } |
| |
| // Up next comes the per-module local analyses that we do for Thin LTO. |
| // Each of these functions is basically copied from the LLVM |
| // implementation and then tailored to suit this implementation. Ideally |
| // each of these would be supported by upstream LLVM but that's perhaps |
| // a patch for another day! |
| // |
| // You can find some more comments about these functions in the LLVM |
| // bindings we've got (currently `PassWrapper.cpp`) |
| { |
| let _timer = cgcx.prof.generic_activity("LLVM_thin_lto_rename"); |
| if !llvm::LLVMRustPrepareThinLTORename(thin_module.shared.data.0, llmod) { |
| let msg = "failed to prepare thin LTO module"; |
| return Err(write::llvm_err(&diag_handler, msg)) |
| } |
| save_temp_bitcode(cgcx, &module, "thin-lto-after-rename"); |
| } |
| |
| { |
| let _timer = cgcx.prof.generic_activity("LLVM_thin_lto_resolve_weak"); |
| if !llvm::LLVMRustPrepareThinLTOResolveWeak(thin_module.shared.data.0, llmod) { |
| let msg = "failed to prepare thin LTO module"; |
| return Err(write::llvm_err(&diag_handler, msg)) |
| } |
| save_temp_bitcode(cgcx, &module, "thin-lto-after-resolve"); |
| } |
| |
| { |
| let _timer = cgcx.prof.generic_activity("LLVM_thin_lto_internalize"); |
| if !llvm::LLVMRustPrepareThinLTOInternalize(thin_module.shared.data.0, llmod) { |
| let msg = "failed to prepare thin LTO module"; |
| return Err(write::llvm_err(&diag_handler, msg)) |
| } |
| save_temp_bitcode(cgcx, &module, "thin-lto-after-internalize"); |
| } |
| |
| { |
| let _timer = cgcx.prof.generic_activity("LLVM_thin_lto_import"); |
| if !llvm::LLVMRustPrepareThinLTOImport(thin_module.shared.data.0, llmod) { |
| let msg = "failed to prepare thin LTO module"; |
| return Err(write::llvm_err(&diag_handler, msg)) |
| } |
| save_temp_bitcode(cgcx, &module, "thin-lto-after-import"); |
| } |
| |
| // Ok now this is a bit unfortunate. This is also something you won't |
| // find upstream in LLVM's ThinLTO passes! This is a hack for now to |
| // work around bugs in LLVM. |
| // |
| // First discovered in #45511 it was found that as part of ThinLTO |
| // importing passes LLVM will import `DICompileUnit` metadata |
| // information across modules. This means that we'll be working with one |
| // LLVM module that has multiple `DICompileUnit` instances in it (a |
| // bunch of `llvm.dbg.cu` members). Unfortunately there's a number of |
| // bugs in LLVM's backend which generates invalid DWARF in a situation |
| // like this: |
| // |
| // https://bugs.llvm.org/show_bug.cgi?id=35212 |
| // https://bugs.llvm.org/show_bug.cgi?id=35562 |
| // |
| // While the first bug there is fixed the second ended up causing #46346 |
| // which was basically a resurgence of #45511 after LLVM's bug 35212 was |
| // fixed. |
| // |
| // This function below is a huge hack around this problem. The function |
| // below is defined in `PassWrapper.cpp` and will basically "merge" |
| // all `DICompileUnit` instances in a module. Basically it'll take all |
| // the objects, rewrite all pointers of `DISubprogram` to point to the |
| // first `DICompileUnit`, and then delete all the other units. |
| // |
| // This is probably mangling to the debug info slightly (but hopefully |
| // not too much) but for now at least gets LLVM to emit valid DWARF (or |
| // so it appears). Hopefully we can remove this once upstream bugs are |
| // fixed in LLVM. |
| { |
| let _timer = cgcx.prof.generic_activity("LLVM_thin_lto_patch_debuginfo"); |
| llvm::LLVMRustThinLTOPatchDICompileUnit(llmod, cu1); |
| save_temp_bitcode(cgcx, &module, "thin-lto-after-patch"); |
| } |
| |
| // Alright now that we've done everything related to the ThinLTO |
| // analysis it's time to run some optimizations! Here we use the same |
| // `run_pass_manager` as the "fat" LTO above except that we tell it to |
| // populate a thin-specific pass manager, which presumably LLVM treats a |
| // little differently. |
| { |
| let _timer = cgcx.prof.generic_activity("LLVM_thin_lto_optimize"); |
| info!("running thin lto passes over {}", module.name); |
| let config = cgcx.config(module.kind); |
| run_pass_manager(cgcx, &module, config, true); |
| save_temp_bitcode(cgcx, &module, "thin-lto-after-pm"); |
| } |
| } |
| Ok(module) |
| } |
| |
| #[derive(Debug, Default)] |
| pub struct ThinLTOImports { |
| // key = llvm name of importing module, value = list of modules it imports from |
| imports: FxHashMap<String, Vec<String>>, |
| } |
| |
| impl ThinLTOImports { |
| fn modules_imported_by(&self, llvm_module_name: &str) -> &[String] { |
| self.imports.get(llvm_module_name).map(|v| &v[..]).unwrap_or(&[]) |
| } |
| |
| /// Loads the ThinLTO import map from ThinLTOData. |
| unsafe fn from_thin_lto_data(data: *const llvm::ThinLTOData) -> ThinLTOImports { |
| unsafe extern "C" fn imported_module_callback(payload: *mut libc::c_void, |
| importing_module_name: *const libc::c_char, |
| imported_module_name: *const libc::c_char) { |
| let map = &mut* (payload as *mut ThinLTOImports); |
| let importing_module_name = CStr::from_ptr(importing_module_name); |
| let importing_module_name = module_name_to_str(&importing_module_name); |
| let imported_module_name = CStr::from_ptr(imported_module_name); |
| let imported_module_name = module_name_to_str(&imported_module_name); |
| |
| if !map.imports.contains_key(importing_module_name) { |
| map.imports.insert(importing_module_name.to_owned(), vec![]); |
| } |
| |
| map.imports |
| .get_mut(importing_module_name) |
| .unwrap() |
| .push(imported_module_name.to_owned()); |
| } |
| let mut map = ThinLTOImports::default(); |
| llvm::LLVMRustGetThinLTOModuleImports(data, |
| imported_module_callback, |
| &mut map as *mut _ as *mut libc::c_void); |
| map |
| } |
| } |
| |
| fn module_name_to_str(c_str: &CStr) -> &str { |
| c_str.to_str().unwrap_or_else(|e| |
| bug!("Encountered non-utf8 LLVM module name `{}`: {}", c_str.to_string_lossy(), e)) |
| } |
| |
| pub fn parse_module<'a>( |
| cx: &'a llvm::Context, |
| name: &CStr, |
| data: &[u8], |
| diag_handler: &Handler, |
| ) -> Result<&'a llvm::Module, FatalError> { |
| unsafe { |
| llvm::LLVMRustParseBitcodeForLTO( |
| cx, |
| data.as_ptr(), |
| data.len(), |
| name.as_ptr(), |
| ).ok_or_else(|| { |
| let msg = "failed to parse bitcode for LTO module"; |
| write::llvm_err(&diag_handler, msg) |
| }) |
| } |
| } |
