rustc_codegen_llvm/
base.rs

1//! Codegen the MIR to the LLVM IR.
2//!
3//! Hopefully useful general knowledge about codegen:
4//!
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`].
10//!
11//! [`Ty`]: rustc_middle::ty::Ty
12//! [`val_ty`]: crate::common::val_ty
13
14use std::time::Instant;
15
16use rustc_attr_ir::Linkage;
17use rustc_codegen_ssa::ModuleCodegen;
18use rustc_codegen_ssa::base::maybe_create_entry_wrapper;
19use rustc_codegen_ssa::mono_item::MonoItemExt;
20use rustc_codegen_ssa::traits::*;
21use rustc_data_structures::small_c_str::SmallCStr;
22use rustc_middle::dep_graph;
23use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrs, SanitizerFnAttrs};
24use rustc_middle::mono::Visibility;
25use rustc_middle::ty::TyCtxt;
26use rustc_session::config::{DebugInfo, Offload};
27use rustc_span::Symbol;
28use rustc_target::spec::SanitizerSet;
29
30use crate::builder::Builder;
31use crate::builder::gpu_offload::OffloadGlobals;
32use crate::context::CodegenCx;
33use crate::llvm::{self, Value};
34use crate::{ModuleLlvm, attributes};
35
36pub(crate) struct ValueIter<'ll> {
37    cur: Option<&'ll Value>,
38    step: unsafe extern "C" fn(&'ll Value) -> Option<&'ll Value>,
39}
40
41impl<'ll> Iterator for ValueIter<'ll> {
42    type Item = &'ll Value;
43
44    fn next(&mut self) -> Option<&'ll Value> {
45        let old = self.cur;
46        if let Some(old) = old {
47            self.cur = unsafe { (self.step)(old) };
48        }
49        old
50    }
51}
52
53pub(crate) fn iter_globals(llmod: &llvm::Module) -> ValueIter<'_> {
54    unsafe { ValueIter { cur: llvm::LLVMGetFirstGlobal(llmod), step: llvm::LLVMGetNextGlobal } }
55}
56
57pub(crate) fn iter_global_aliases(llmod: &llvm::Module) -> ValueIter<'_> {
58    unsafe {
59        ValueIter { cur: llvm::LLVMGetFirstGlobalAlias(llmod), step: llvm::LLVMGetNextGlobalAlias }
60    }
61}
62
63pub(crate) fn compile_codegen_unit(
64    tcx: TyCtxt<'_>,
65    cgu_name: Symbol,
66    bitcode_needed: bool,
67) -> (ModuleCodegen<ModuleLlvm>, u64) {
68    let start_time = Instant::now();
69
70    let dep_node = tcx.codegen_unit(cgu_name).codegen_dep_node(tcx);
71    let (module, _) = tcx.dep_graph.with_task(
72        dep_node,
73        tcx,
74        || module_codegen(tcx, cgu_name, bitcode_needed),
75        Some(dep_graph::hash_result),
76    );
77    let time_to_codegen = start_time.elapsed();
78
79    // We assume that the cost to run LLVM on a CGU is proportional to
80    // the time we needed for codegenning it.
81    let cost = time_to_codegen.as_nanos() as u64;
82
83    fn module_codegen(
84        tcx: TyCtxt<'_>,
85        cgu_name: Symbol,
86        needs_bitcode: bool,
87    ) -> ModuleCodegen<ModuleLlvm> {
88        let cgu = tcx.codegen_unit(cgu_name);
89        let _prof_timer =
90            tcx.prof.generic_activity_with_arg_recorder("codegen_module", |recorder| {
91                recorder.record_arg(cgu_name.to_string());
92                recorder.record_arg(cgu.size_estimate().to_string());
93            });
94        // Instantiate monomorphizations without filling out definitions yet...
95        let llvm_module = ModuleLlvm::new(tcx, cgu_name.as_str());
96        {
97            let mut cx = CodegenCx::new(tcx, cgu, &llvm_module, needs_bitcode);
98
99            // Declare and store globals shared by all offload kernels
100            //
101            // These globals are left in the LLVM-IR host module so all kernels can access them.
102            // They are necessary for correct offload execution. We do this here to simplify the
103            // `offload` intrinsic, avoiding the need for tracking whether it's the first
104            // intrinsic call or not.
105            let has_host_offload = cx
106                .sess()
107                .opts
108                .unstable_opts
109                .offload
110                .iter()
111                .any(|o| #[allow(non_exhaustive_omitted_patterns)] match o {
    Offload::Host(_) | Offload::Test => true,
    _ => false,
}matches!(o, Offload::Host(_) | Offload::Test));
112            if has_host_offload && !cx.sess().target.is_like_gpu {
113                cx.offload_globals.replace(Some(OffloadGlobals::declare(&cx)));
114            }
115
116            let mono_items = cx.codegen_unit.items_in_deterministic_order(cx.tcx);
117            for &(mono_item, data) in &mono_items {
118                mono_item.predefine::<Builder<'_, '_, '_>>(
119                    &mut cx,
120                    cgu_name.as_str(),
121                    data.linkage,
122                    data.visibility,
123                );
124            }
125
126            // ... and now that we have everything pre-defined, fill out those definitions.
127            for &(mono_item, item_data) in &mono_items {
128                mono_item.define::<Builder<'_, '_, '_>>(&mut cx, cgu_name.as_str(), item_data);
129            }
130
131            // If this codegen unit contains the main function, also create the
132            // wrapper here
133            if let Some(entry) =
134                maybe_create_entry_wrapper::<Builder<'_, '_, '_>>(&cx, cx.codegen_unit)
135            {
136                let mut attrs =
137                    attributes::sanitize_attrs(&cx, tcx, SanitizerFnAttrs::default(), None, None);
138                // When pointer authentication is enabled, ensure that the ptrauth-* attributes are
139                // also attached to the entry wrapper.
140                //
141                // FIXME(jchlanda) If it ever becomes necessary to ensure that all compiler
142                // generated functions receive the ptrauth-* attributes, `declare_fn` or
143                // `declare_raw_fn` could be used to provide those.
144                if cx.sess().pointer_authentication() {
145                    let cfg = cx.sess().pointer_auth_config.as_ref().unwrap();
146                    for ptrauth_attr in cfg.fn_attrs() {
147                        attrs.push(llvm::CreateAttrString(cx.llcx, ptrauth_attr));
148                    }
149                }
150                attributes::apply_to_llfn(entry, llvm::AttributePlace::Function, &attrs);
151            }
152
153            // Define Objective-C module info and module flags. Note, the module info will
154            // also be added to the `llvm.compiler.used` variable, created later.
155            //
156            // These are only necessary when we need the linker to do its Objective-C-specific
157            // magic. We could theoretically do it unconditionally, but at a slight cost to linker
158            // performance in the common case where it's unnecessary.
159            if !cx.objc_classrefs.borrow().is_empty() || !cx.objc_selrefs.borrow().is_empty() {
160                if cx.objc_abi_version() == 1 {
161                    cx.define_objc_module_info();
162                }
163                cx.add_objc_module_flags();
164            }
165
166            if cx.sess().pointer_authentication() {
167                let cfg = cx.sess().pointer_auth_config.as_ref().unwrap();
168
169                let aarch64_elf_pauthabi_version =
170                    cfg.calculate_pauth_abi_version(&cx.sess().target);
171                if aarch64_elf_pauthabi_version != 0 {
172                    cx.add_ptrauth_pauthabi_version_and_platform_flags(
173                        aarch64_elf_pauthabi_version,
174                    );
175                }
176                if cfg.elf_got {
177                    cx.add_ptrauth_elf_got_flag();
178                }
179                if cx.sess().pointer_authentication_functions().is_some() {
180                    cx.add_ptrauth_sign_personality_flag();
181                }
182            }
183
184            // Finalize code coverage by injecting the coverage map. Note, the coverage map will
185            // also be added to the `llvm.compiler.used` variable, created next.
186            if cx.sess().instrument_coverage() {
187                cx.coverageinfo_finalize();
188            }
189
190            // Create the llvm.used variable.
191            if !cx.used_statics.is_empty() {
192                cx.create_used_variable_impl(c"llvm.used", &cx.used_statics);
193            }
194
195            // Create the llvm.compiler.used variable.
196            {
197                let compiler_used_statics = cx.compiler_used_statics.borrow();
198                if !compiler_used_statics.is_empty() {
199                    cx.create_used_variable_impl(c"llvm.compiler.used", &compiler_used_statics);
200                }
201            }
202
203            // Run replace-all-uses-with for statics that need it. This must
204            // happen after the llvm.used variables are created.
205            for &(old_g, new_g) in cx.statics_to_rauw().borrow().iter() {
206                unsafe {
207                    llvm::LLVMReplaceAllUsesWith(old_g, new_g);
208                    llvm::LLVMDeleteGlobal(old_g);
209                }
210            }
211
212            // Finalize debuginfo
213            if cx.sess().opts.debuginfo != DebugInfo::None {
214                cx.debuginfo_finalize();
215            }
216        }
217
218        ModuleCodegen::new_regular(cgu_name.to_string(), llvm_module)
219    }
220
221    (module, cost)
222}
223
224pub(crate) fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
225    let Some(sect) = attrs.link_section else { return };
226    let buf = SmallCStr::new(sect.as_str());
227    llvm::set_section(llval, &buf);
228}
229
230pub(crate) fn linkage_to_llvm(linkage: Linkage) -> llvm::Linkage {
231    match linkage {
232        Linkage::External => llvm::Linkage::ExternalLinkage,
233        Linkage::AvailableExternally => llvm::Linkage::AvailableExternallyLinkage,
234        Linkage::LinkOnceAny => llvm::Linkage::LinkOnceAnyLinkage,
235        Linkage::LinkOnceODR => llvm::Linkage::LinkOnceODRLinkage,
236        Linkage::WeakAny => llvm::Linkage::WeakAnyLinkage,
237        Linkage::WeakODR => llvm::Linkage::WeakODRLinkage,
238        Linkage::Internal => llvm::Linkage::InternalLinkage,
239        Linkage::ExternalWeak => llvm::Linkage::ExternalWeakLinkage,
240    }
241}
242
243pub(crate) fn visibility_to_llvm(linkage: Visibility) -> llvm::Visibility {
244    match linkage {
245        Visibility::Default => llvm::Visibility::Default,
246        Visibility::Hidden => llvm::Visibility::Hidden,
247        Visibility::Protected => llvm::Visibility::Protected,
248    }
249}
250
251pub(crate) fn set_variable_sanitizer_attrs(llval: &Value, attrs: &CodegenFnAttrs) {
252    if attrs.sanitizers.disabled.contains(SanitizerSet::ADDRESS)
253        || attrs.sanitizers.disabled.contains(SanitizerSet::KERNELADDRESS)
254    {
255        unsafe { llvm::LLVMRustSetNoSanitizeAddress(llval) };
256    }
257    if attrs.sanitizers.disabled.contains(SanitizerSet::HWADDRESS)
258        || attrs.sanitizers.disabled.contains(SanitizerSet::KERNELHWADDRESS)
259    {
260        unsafe { llvm::LLVMRustSetNoSanitizeHWAddress(llval) };
261    }
262}
rustc_codegen_llvm/base.rs

rustc_codegen_llvm/
base.rs
