rustc_codegen_llvm/
context.rs

1use std::borrow::{Borrow, Cow};
2use std::cell::{Cell, RefCell};
3use std::ffi::{CStr, c_char, c_uint};
4use std::marker::PhantomData;
5use std::ops::{Deref, DerefMut};
6use std::str;
7
8use rustc_abi::{HasDataLayout, Size, TargetDataLayout, VariantIdx};
9use rustc_codegen_ssa::back::versioned_llvm_target;
10use rustc_codegen_ssa::base::{wants_msvc_seh, wants_wasm_eh};
11use rustc_codegen_ssa::errors as ssa_errors;
12use rustc_codegen_ssa::traits::*;
13use rustc_data_structures::base_n::{ALPHANUMERIC_ONLY, ToBaseN};
14use rustc_data_structures::fx::FxHashMap;
15use rustc_data_structures::small_c_str::SmallCStr;
16use rustc_hir::def_id::DefId;
17use rustc_middle::middle::codegen_fn_attrs::PatchableFunctionEntry;
18use rustc_middle::mir::mono::CodegenUnit;
19use rustc_middle::ty::layout::{
20    FnAbiError, FnAbiOfHelpers, FnAbiRequest, HasTypingEnv, LayoutError, LayoutOfHelpers,
21};
22use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
23use rustc_middle::{bug, span_bug};
24use rustc_session::Session;
25use rustc_session::config::{
26    BranchProtection, CFGuard, CFProtection, CrateType, DebugInfo, FunctionReturn, PAuthKey, PacRet,
27};
28use rustc_span::source_map::Spanned;
29use rustc_span::{DUMMY_SP, Span};
30use rustc_symbol_mangling::mangle_internal_symbol;
31use rustc_target::spec::{HasTargetSpec, RelocModel, SmallDataThresholdSupport, Target, TlsModel};
32use smallvec::SmallVec;
33
34use crate::back::write::to_llvm_code_model;
35use crate::callee::get_fn;
36use crate::debuginfo::metadata::apply_vcall_visibility_metadata;
37use crate::llvm::Metadata;
38use crate::type_::Type;
39use crate::value::Value;
40use crate::{attributes, common, coverageinfo, debuginfo, llvm, llvm_util};
41
42/// `TyCtxt` (and related cache datastructures) can't be move between threads.
43/// However, there are various cx related functions which we want to be available to the builder and
44/// other compiler pieces. Here we define a small subset which has enough information and can be
45/// moved around more freely.
46pub(crate) struct SCx<'ll> {
47    pub llmod: &'ll llvm::Module,
48    pub llcx: &'ll llvm::Context,
49    pub isize_ty: &'ll Type,
50}
51
52impl<'ll> Borrow<SCx<'ll>> for FullCx<'ll, '_> {
53    fn borrow(&self) -> &SCx<'ll> {
54        &self.scx
55    }
56}
57
58impl<'ll, 'tcx> Deref for FullCx<'ll, 'tcx> {
59    type Target = SimpleCx<'ll>;
60
61    #[inline]
62    fn deref(&self) -> &Self::Target {
63        &self.scx
64    }
65}
66
67pub(crate) struct GenericCx<'ll, T: Borrow<SCx<'ll>>>(T, PhantomData<SCx<'ll>>);
68
69impl<'ll, T: Borrow<SCx<'ll>>> Deref for GenericCx<'ll, T> {
70    type Target = T;
71
72    #[inline]
73    fn deref(&self) -> &Self::Target {
74        &self.0
75    }
76}
77
78impl<'ll, T: Borrow<SCx<'ll>>> DerefMut for GenericCx<'ll, T> {
79    #[inline]
80    fn deref_mut(&mut self) -> &mut Self::Target {
81        &mut self.0
82    }
83}
84
85pub(crate) type SimpleCx<'ll> = GenericCx<'ll, SCx<'ll>>;
86
87/// There is one `CodegenCx` per codegen unit. Each one has its own LLVM
88/// `llvm::Context` so that several codegen units may be processed in parallel.
89/// All other LLVM data structures in the `CodegenCx` are tied to that `llvm::Context`.
90pub(crate) type CodegenCx<'ll, 'tcx> = GenericCx<'ll, FullCx<'ll, 'tcx>>;
91
92pub(crate) struct FullCx<'ll, 'tcx> {
93    pub tcx: TyCtxt<'tcx>,
94    pub scx: SimpleCx<'ll>,
95    pub use_dll_storage_attrs: bool,
96    pub tls_model: llvm::ThreadLocalMode,
97
98    pub codegen_unit: &'tcx CodegenUnit<'tcx>,
99
100    /// Cache instances of monomorphic and polymorphic items
101    pub instances: RefCell<FxHashMap<Instance<'tcx>, &'ll Value>>,
102    /// Cache generated vtables
103    pub vtables: RefCell<FxHashMap<(Ty<'tcx>, Option<ty::ExistentialTraitRef<'tcx>>), &'ll Value>>,
104    /// Cache of constant strings,
105    pub const_str_cache: RefCell<FxHashMap<String, &'ll Value>>,
106
107    /// Cache of emitted const globals (value -> global)
108    pub const_globals: RefCell<FxHashMap<&'ll Value, &'ll Value>>,
109
110    /// List of globals for static variables which need to be passed to the
111    /// LLVM function ReplaceAllUsesWith (RAUW) when codegen is complete.
112    /// (We have to make sure we don't invalidate any Values referring
113    /// to constants.)
114    pub statics_to_rauw: RefCell<Vec<(&'ll Value, &'ll Value)>>,
115
116    /// Statics that will be placed in the llvm.used variable
117    /// See <https://llvm.org/docs/LangRef.html#the-llvm-used-global-variable> for details
118    pub used_statics: Vec<&'ll Value>,
119
120    /// Statics that will be placed in the llvm.compiler.used variable
121    /// See <https://llvm.org/docs/LangRef.html#the-llvm-compiler-used-global-variable> for details
122    pub compiler_used_statics: Vec<&'ll Value>,
123
124    /// Mapping of non-scalar types to llvm types.
125    pub type_lowering: RefCell<FxHashMap<(Ty<'tcx>, Option<VariantIdx>), &'ll Type>>,
126
127    /// Mapping of scalar types to llvm types.
128    pub scalar_lltypes: RefCell<FxHashMap<Ty<'tcx>, &'ll Type>>,
129
130    /// Extra per-CGU codegen state needed when coverage instrumentation is enabled.
131    pub coverage_cx: Option<coverageinfo::CguCoverageContext<'ll, 'tcx>>,
132    pub dbg_cx: Option<debuginfo::CodegenUnitDebugContext<'ll, 'tcx>>,
133
134    eh_personality: Cell<Option<&'ll Value>>,
135    eh_catch_typeinfo: Cell<Option<&'ll Value>>,
136    pub rust_try_fn: Cell<Option<(&'ll Type, &'ll Value)>>,
137
138    intrinsics:
139        RefCell<FxHashMap<(Cow<'static, str>, SmallVec<[&'ll Type; 2]>), (&'ll Type, &'ll Value)>>,
140
141    /// A counter that is used for generating local symbol names
142    local_gen_sym_counter: Cell<usize>,
143
144    /// `codegen_static` will sometimes create a second global variable with a
145    /// different type and clear the symbol name of the original global.
146    /// `global_asm!` needs to be able to find this new global so that it can
147    /// compute the correct mangled symbol name to insert into the asm.
148    pub renamed_statics: RefCell<FxHashMap<DefId, &'ll Value>>,
149}
150
151fn to_llvm_tls_model(tls_model: TlsModel) -> llvm::ThreadLocalMode {
152    match tls_model {
153        TlsModel::GeneralDynamic => llvm::ThreadLocalMode::GeneralDynamic,
154        TlsModel::LocalDynamic => llvm::ThreadLocalMode::LocalDynamic,
155        TlsModel::InitialExec => llvm::ThreadLocalMode::InitialExec,
156        TlsModel::LocalExec => llvm::ThreadLocalMode::LocalExec,
157        TlsModel::Emulated => llvm::ThreadLocalMode::GeneralDynamic,
158    }
159}
160
161pub(crate) unsafe fn create_module<'ll>(
162    tcx: TyCtxt<'_>,
163    llcx: &'ll llvm::Context,
164    mod_name: &str,
165) -> &'ll llvm::Module {
166    let sess = tcx.sess;
167    let mod_name = SmallCStr::new(mod_name);
168    let llmod = unsafe { llvm::LLVMModuleCreateWithNameInContext(mod_name.as_ptr(), llcx) };
169
170    let cx = SimpleCx::new(llmod, llcx, tcx.data_layout.pointer_size());
171
172    let mut target_data_layout = sess.target.data_layout.to_string();
173    let llvm_version = llvm_util::get_version();
174
175    if llvm_version < (20, 0, 0) {
176        if sess.target.arch == "aarch64" || sess.target.arch.starts_with("arm64") {
177            // LLVM 20 defines three additional address spaces for alternate
178            // pointer kinds used in Windows.
179            // See https://github.com/llvm/llvm-project/pull/111879
180            target_data_layout =
181                target_data_layout.replace("-p270:32:32-p271:32:32-p272:64:64", "");
182        }
183        if sess.target.arch.starts_with("sparc") {
184            // LLVM 20 updates the sparc layout to correctly align 128 bit integers to 128 bit.
185            // See https://github.com/llvm/llvm-project/pull/106951
186            target_data_layout = target_data_layout.replace("-i128:128", "");
187        }
188        if sess.target.arch.starts_with("mips64") {
189            // LLVM 20 updates the mips64 layout to correctly align 128 bit integers to 128 bit.
190            // See https://github.com/llvm/llvm-project/pull/112084
191            target_data_layout = target_data_layout.replace("-i128:128", "");
192        }
193        if sess.target.arch.starts_with("powerpc64") {
194            // LLVM 20 updates the powerpc64 layout to correctly align 128 bit integers to 128 bit.
195            // See https://github.com/llvm/llvm-project/pull/118004
196            target_data_layout = target_data_layout.replace("-i128:128", "");
197        }
198        if sess.target.arch.starts_with("wasm32") || sess.target.arch.starts_with("wasm64") {
199            // LLVM 20 updates the wasm(32|64) layout to correctly align 128 bit integers to 128 bit.
200            // See https://github.com/llvm/llvm-project/pull/119204
201            target_data_layout = target_data_layout.replace("-i128:128", "");
202        }
203    }
204    if llvm_version < (21, 0, 0) {
205        if sess.target.arch == "nvptx64" {
206            // LLVM 21 updated the default layout on nvptx: https://github.com/llvm/llvm-project/pull/124961
207            target_data_layout = target_data_layout.replace("e-p6:32:32-i64", "e-i64");
208        }
209        if sess.target.arch == "amdgpu" {
210            // LLVM 21 adds the address width for address space 8.
211            // See https://github.com/llvm/llvm-project/pull/139419
212            target_data_layout = target_data_layout.replace("p8:128:128:128:48", "p8:128:128")
213        }
214    }
215    if llvm_version < (22, 0, 0) {
216        if sess.target.arch == "avr" {
217            // LLVM 22.0 updated the default layout on avr: https://github.com/llvm/llvm-project/pull/153010
218            target_data_layout = target_data_layout.replace("n8:16", "n8")
219        }
220        if sess.target.arch == "nvptx64" {
221            // LLVM 22 updated the NVPTX layout to indicate 256-bit vector load/store: https://github.com/llvm/llvm-project/pull/155198
222            target_data_layout = target_data_layout.replace("-i256:256", "");
223        }
224    }
225
226    // Ensure the data-layout values hardcoded remain the defaults.
227    {
228        let tm = crate::back::write::create_informational_target_machine(sess, false);
229        unsafe {
230            llvm::LLVMRustSetDataLayoutFromTargetMachine(llmod, tm.raw());
231        }
232
233        let llvm_data_layout = unsafe { llvm::LLVMGetDataLayoutStr(llmod) };
234        let llvm_data_layout =
235            str::from_utf8(unsafe { CStr::from_ptr(llvm_data_layout) }.to_bytes())
236                .expect("got a non-UTF8 data-layout from LLVM");
237
238        if target_data_layout != llvm_data_layout {
239            tcx.dcx().emit_err(crate::errors::MismatchedDataLayout {
240                rustc_target: sess.opts.target_triple.to_string().as_str(),
241                rustc_layout: target_data_layout.as_str(),
242                llvm_target: sess.target.llvm_target.borrow(),
243                llvm_layout: llvm_data_layout,
244            });
245        }
246    }
247
248    let data_layout = SmallCStr::new(&target_data_layout);
249    unsafe {
250        llvm::LLVMSetDataLayout(llmod, data_layout.as_ptr());
251    }
252
253    let llvm_target = SmallCStr::new(&versioned_llvm_target(sess));
254    unsafe {
255        llvm::LLVMRustSetNormalizedTarget(llmod, llvm_target.as_ptr());
256    }
257
258    let reloc_model = sess.relocation_model();
259    if matches!(reloc_model, RelocModel::Pic | RelocModel::Pie) {
260        unsafe {
261            llvm::LLVMRustSetModulePICLevel(llmod);
262        }
263        // PIE is potentially more effective than PIC, but can only be used in executables.
264        // If all our outputs are executables, then we can relax PIC to PIE.
265        if reloc_model == RelocModel::Pie
266            || tcx.crate_types().iter().all(|ty| *ty == CrateType::Executable)
267        {
268            unsafe {
269                llvm::LLVMRustSetModulePIELevel(llmod);
270            }
271        }
272    }
273
274    // Linking object files with different code models is undefined behavior
275    // because the compiler would have to generate additional code (to span
276    // longer jumps) if a larger code model is used with a smaller one.
277    //
278    // See https://reviews.llvm.org/D52322 and https://reviews.llvm.org/D52323.
279    unsafe {
280        llvm::LLVMRustSetModuleCodeModel(llmod, to_llvm_code_model(sess.code_model()));
281    }
282
283    // If skipping the PLT is enabled, we need to add some module metadata
284    // to ensure intrinsic calls don't use it.
285    if !sess.needs_plt() {
286        llvm::add_module_flag_u32(llmod, llvm::ModuleFlagMergeBehavior::Warning, "RtLibUseGOT", 1);
287    }
288
289    // Enable canonical jump tables if CFI is enabled. (See https://reviews.llvm.org/D65629.)
290    if sess.is_sanitizer_cfi_canonical_jump_tables_enabled() && sess.is_sanitizer_cfi_enabled() {
291        llvm::add_module_flag_u32(
292            llmod,
293            llvm::ModuleFlagMergeBehavior::Override,
294            "CFI Canonical Jump Tables",
295            1,
296        );
297    }
298
299    // If we're normalizing integers with CFI, ensure LLVM generated functions do the same.
300    // See https://github.com/llvm/llvm-project/pull/104826
301    if sess.is_sanitizer_cfi_normalize_integers_enabled() {
302        llvm::add_module_flag_u32(
303            llmod,
304            llvm::ModuleFlagMergeBehavior::Override,
305            "cfi-normalize-integers",
306            1,
307        );
308    }
309
310    // Enable LTO unit splitting if specified or if CFI is enabled. (See
311    // https://reviews.llvm.org/D53891.)
312    if sess.is_split_lto_unit_enabled() || sess.is_sanitizer_cfi_enabled() {
313        llvm::add_module_flag_u32(
314            llmod,
315            llvm::ModuleFlagMergeBehavior::Override,
316            "EnableSplitLTOUnit",
317            1,
318        );
319    }
320
321    // Add "kcfi" module flag if KCFI is enabled. (See https://reviews.llvm.org/D119296.)
322    if sess.is_sanitizer_kcfi_enabled() {
323        llvm::add_module_flag_u32(llmod, llvm::ModuleFlagMergeBehavior::Override, "kcfi", 1);
324
325        // Add "kcfi-offset" module flag with -Z patchable-function-entry (See
326        // https://reviews.llvm.org/D141172).
327        let pfe =
328            PatchableFunctionEntry::from_config(sess.opts.unstable_opts.patchable_function_entry);
329        if pfe.prefix() > 0 {
330            llvm::add_module_flag_u32(
331                llmod,
332                llvm::ModuleFlagMergeBehavior::Override,
333                "kcfi-offset",
334                pfe.prefix().into(),
335            );
336        }
337
338        // Add "kcfi-arity" module flag if KCFI arity indicator is enabled. (See
339        // https://github.com/llvm/llvm-project/pull/117121.)
340        if sess.is_sanitizer_kcfi_arity_enabled() {
341            // KCFI arity indicator requires LLVM 21.0.0 or later.
342            if llvm_version < (21, 0, 0) {
343                tcx.dcx().emit_err(crate::errors::SanitizerKcfiArityRequiresLLVM2100);
344            }
345
346            llvm::add_module_flag_u32(
347                llmod,
348                llvm::ModuleFlagMergeBehavior::Override,
349                "kcfi-arity",
350                1,
351            );
352        }
353    }
354
355    // Control Flow Guard is currently only supported by MSVC and LLVM on Windows.
356    if sess.target.is_like_msvc
357        || (sess.target.options.os == "windows"
358            && sess.target.options.env == "gnu"
359            && sess.target.options.abi == "llvm")
360    {
361        match sess.opts.cg.control_flow_guard {
362            CFGuard::Disabled => {}
363            CFGuard::NoChecks => {
364                // Set `cfguard=1` module flag to emit metadata only.
365                llvm::add_module_flag_u32(
366                    llmod,
367                    llvm::ModuleFlagMergeBehavior::Warning,
368                    "cfguard",
369                    1,
370                );
371            }
372            CFGuard::Checks => {
373                // Set `cfguard=2` module flag to emit metadata and checks.
374                llvm::add_module_flag_u32(
375                    llmod,
376                    llvm::ModuleFlagMergeBehavior::Warning,
377                    "cfguard",
378                    2,
379                );
380            }
381        }
382    }
383
384    if let Some(regparm_count) = sess.opts.unstable_opts.regparm {
385        llvm::add_module_flag_u32(
386            llmod,
387            llvm::ModuleFlagMergeBehavior::Error,
388            "NumRegisterParameters",
389            regparm_count,
390        );
391    }
392
393    if let Some(BranchProtection { bti, pac_ret }) = sess.opts.unstable_opts.branch_protection {
394        if sess.target.arch == "aarch64" {
395            llvm::add_module_flag_u32(
396                llmod,
397                llvm::ModuleFlagMergeBehavior::Min,
398                "branch-target-enforcement",
399                bti.into(),
400            );
401            llvm::add_module_flag_u32(
402                llmod,
403                llvm::ModuleFlagMergeBehavior::Min,
404                "sign-return-address",
405                pac_ret.is_some().into(),
406            );
407            let pac_opts = pac_ret.unwrap_or(PacRet { leaf: false, pc: false, key: PAuthKey::A });
408            llvm::add_module_flag_u32(
409                llmod,
410                llvm::ModuleFlagMergeBehavior::Min,
411                "branch-protection-pauth-lr",
412                pac_opts.pc.into(),
413            );
414            llvm::add_module_flag_u32(
415                llmod,
416                llvm::ModuleFlagMergeBehavior::Min,
417                "sign-return-address-all",
418                pac_opts.leaf.into(),
419            );
420            llvm::add_module_flag_u32(
421                llmod,
422                llvm::ModuleFlagMergeBehavior::Min,
423                "sign-return-address-with-bkey",
424                u32::from(pac_opts.key == PAuthKey::B),
425            );
426        } else {
427            bug!(
428                "branch-protection used on non-AArch64 target; \
429                  this should be checked in rustc_session."
430            );
431        }
432    }
433
434    // Pass on the control-flow protection flags to LLVM (equivalent to `-fcf-protection` in Clang).
435    if let CFProtection::Branch | CFProtection::Full = sess.opts.unstable_opts.cf_protection {
436        llvm::add_module_flag_u32(
437            llmod,
438            llvm::ModuleFlagMergeBehavior::Override,
439            "cf-protection-branch",
440            1,
441        );
442    }
443    if let CFProtection::Return | CFProtection::Full = sess.opts.unstable_opts.cf_protection {
444        llvm::add_module_flag_u32(
445            llmod,
446            llvm::ModuleFlagMergeBehavior::Override,
447            "cf-protection-return",
448            1,
449        );
450    }
451
452    if sess.opts.unstable_opts.virtual_function_elimination {
453        llvm::add_module_flag_u32(
454            llmod,
455            llvm::ModuleFlagMergeBehavior::Error,
456            "Virtual Function Elim",
457            1,
458        );
459    }
460
461    // Set module flag to enable Windows EHCont Guard (/guard:ehcont).
462    if sess.opts.unstable_opts.ehcont_guard {
463        llvm::add_module_flag_u32(llmod, llvm::ModuleFlagMergeBehavior::Warning, "ehcontguard", 1);
464    }
465
466    match sess.opts.unstable_opts.function_return {
467        FunctionReturn::Keep => {}
468        FunctionReturn::ThunkExtern => {
469            llvm::add_module_flag_u32(
470                llmod,
471                llvm::ModuleFlagMergeBehavior::Override,
472                "function_return_thunk_extern",
473                1,
474            );
475        }
476    }
477
478    if sess.opts.unstable_opts.indirect_branch_cs_prefix {
479        llvm::add_module_flag_u32(
480            llmod,
481            llvm::ModuleFlagMergeBehavior::Override,
482            "indirect_branch_cs_prefix",
483            1,
484        );
485    }
486
487    match (sess.opts.unstable_opts.small_data_threshold, sess.target.small_data_threshold_support())
488    {
489        // Set up the small-data optimization limit for architectures that use
490        // an LLVM module flag to control this.
491        (Some(threshold), SmallDataThresholdSupport::LlvmModuleFlag(flag)) => {
492            llvm::add_module_flag_u32(
493                llmod,
494                llvm::ModuleFlagMergeBehavior::Error,
495                &flag,
496                threshold as u32,
497            );
498        }
499        _ => (),
500    };
501
502    // Insert `llvm.ident` metadata.
503    //
504    // On the wasm targets it will get hooked up to the "producer" sections
505    // `processed-by` information.
506    #[allow(clippy::option_env_unwrap)]
507    let rustc_producer =
508        format!("rustc version {}", option_env!("CFG_VERSION").expect("CFG_VERSION"));
509
510    let name_metadata = cx.create_metadata(rustc_producer.as_bytes());
511
512    unsafe {
513        llvm::LLVMAddNamedMetadataOperand(
514            llmod,
515            c"llvm.ident".as_ptr(),
516            &cx.get_metadata_value(llvm::LLVMMDNodeInContext2(llcx, &name_metadata, 1)),
517        );
518    }
519
520    // Emit RISC-V specific target-abi metadata
521    // to workaround lld as the LTO plugin not
522    // correctly setting target-abi for the LTO object
523    // FIXME: https://github.com/llvm/llvm-project/issues/50591
524    // If llvm_abiname is empty, emit nothing.
525    let llvm_abiname = &sess.target.options.llvm_abiname;
526    if matches!(sess.target.arch.as_ref(), "riscv32" | "riscv64") && !llvm_abiname.is_empty() {
527        llvm::add_module_flag_str(
528            llmod,
529            llvm::ModuleFlagMergeBehavior::Error,
530            "target-abi",
531            llvm_abiname,
532        );
533    }
534
535    // Add module flags specified via -Z llvm_module_flag
536    for (key, value, merge_behavior) in &sess.opts.unstable_opts.llvm_module_flag {
537        let merge_behavior = match merge_behavior.as_str() {
538            "error" => llvm::ModuleFlagMergeBehavior::Error,
539            "warning" => llvm::ModuleFlagMergeBehavior::Warning,
540            "require" => llvm::ModuleFlagMergeBehavior::Require,
541            "override" => llvm::ModuleFlagMergeBehavior::Override,
542            "append" => llvm::ModuleFlagMergeBehavior::Append,
543            "appendunique" => llvm::ModuleFlagMergeBehavior::AppendUnique,
544            "max" => llvm::ModuleFlagMergeBehavior::Max,
545            "min" => llvm::ModuleFlagMergeBehavior::Min,
546            // We already checked this during option parsing
547            _ => unreachable!(),
548        };
549        llvm::add_module_flag_u32(llmod, merge_behavior, key, *value);
550    }
551
552    llmod
553}
554
555impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
556    pub(crate) fn new(
557        tcx: TyCtxt<'tcx>,
558        codegen_unit: &'tcx CodegenUnit<'tcx>,
559        llvm_module: &'ll crate::ModuleLlvm,
560    ) -> Self {
561        // An interesting part of Windows which MSVC forces our hand on (and
562        // apparently MinGW didn't) is the usage of `dllimport` and `dllexport`
563        // attributes in LLVM IR as well as native dependencies (in C these
564        // correspond to `__declspec(dllimport)`).
565        //
566        // LD (BFD) in MinGW mode can often correctly guess `dllexport` but
567        // relying on that can result in issues like #50176.
568        // LLD won't support that and expects symbols with proper attributes.
569        // Because of that we make MinGW target emit dllexport just like MSVC.
570        // When it comes to dllimport we use it for constants but for functions
571        // rely on the linker to do the right thing. Opposed to dllexport this
572        // task is easy for them (both LD and LLD) and allows us to easily use
573        // symbols from static libraries in shared libraries.
574        //
575        // Whenever a dynamic library is built on Windows it must have its public
576        // interface specified by functions tagged with `dllexport` or otherwise
577        // they're not available to be linked against. This poses a few problems
578        // for the compiler, some of which are somewhat fundamental, but we use
579        // the `use_dll_storage_attrs` variable below to attach the `dllexport`
580        // attribute to all LLVM functions that are exported e.g., they're
581        // already tagged with external linkage). This is suboptimal for a few
582        // reasons:
583        //
584        // * If an object file will never be included in a dynamic library,
585        //   there's no need to attach the dllexport attribute. Most object
586        //   files in Rust are not destined to become part of a dll as binaries
587        //   are statically linked by default.
588        // * If the compiler is emitting both an rlib and a dylib, the same
589        //   source object file is currently used but with MSVC this may be less
590        //   feasible. The compiler may be able to get around this, but it may
591        //   involve some invasive changes to deal with this.
592        //
593        // The flip side of this situation is that whenever you link to a dll and
594        // you import a function from it, the import should be tagged with
595        // `dllimport`. At this time, however, the compiler does not emit
596        // `dllimport` for any declarations other than constants (where it is
597        // required), which is again suboptimal for even more reasons!
598        //
599        // * Calling a function imported from another dll without using
600        //   `dllimport` causes the linker/compiler to have extra overhead (one
601        //   `jmp` instruction on x86) when calling the function.
602        // * The same object file may be used in different circumstances, so a
603        //   function may be imported from a dll if the object is linked into a
604        //   dll, but it may be just linked against if linked into an rlib.
605        // * The compiler has no knowledge about whether native functions should
606        //   be tagged dllimport or not.
607        //
608        // For now the compiler takes the perf hit (I do not have any numbers to
609        // this effect) by marking very little as `dllimport` and praying the
610        // linker will take care of everything. Fixing this problem will likely
611        // require adding a few attributes to Rust itself (feature gated at the
612        // start) and then strongly recommending static linkage on Windows!
613        let use_dll_storage_attrs = tcx.sess.target.is_like_windows;
614
615        let tls_model = to_llvm_tls_model(tcx.sess.tls_model());
616
617        let (llcx, llmod) = (&*llvm_module.llcx, llvm_module.llmod());
618
619        let coverage_cx =
620            tcx.sess.instrument_coverage().then(coverageinfo::CguCoverageContext::new);
621
622        let dbg_cx = if tcx.sess.opts.debuginfo != DebugInfo::None {
623            let dctx = debuginfo::CodegenUnitDebugContext::new(llmod);
624            debuginfo::metadata::build_compile_unit_di_node(
625                tcx,
626                codegen_unit.name().as_str(),
627                &dctx,
628            );
629            Some(dctx)
630        } else {
631            None
632        };
633
634        GenericCx(
635            FullCx {
636                tcx,
637                scx: SimpleCx::new(llmod, llcx, tcx.data_layout.pointer_size()),
638                use_dll_storage_attrs,
639                tls_model,
640                codegen_unit,
641                instances: Default::default(),
642                vtables: Default::default(),
643                const_str_cache: Default::default(),
644                const_globals: Default::default(),
645                statics_to_rauw: RefCell::new(Vec::new()),
646                used_statics: Vec::new(),
647                compiler_used_statics: Vec::new(),
648                type_lowering: Default::default(),
649                scalar_lltypes: Default::default(),
650                coverage_cx,
651                dbg_cx,
652                eh_personality: Cell::new(None),
653                eh_catch_typeinfo: Cell::new(None),
654                rust_try_fn: Cell::new(None),
655                intrinsics: Default::default(),
656                local_gen_sym_counter: Cell::new(0),
657                renamed_statics: Default::default(),
658            },
659            PhantomData,
660        )
661    }
662
663    pub(crate) fn statics_to_rauw(&self) -> &RefCell<Vec<(&'ll Value, &'ll Value)>> {
664        &self.statics_to_rauw
665    }
666
667    /// Extra state that is only available when coverage instrumentation is enabled.
668    #[inline]
669    #[track_caller]
670    pub(crate) fn coverage_cx(&self) -> &coverageinfo::CguCoverageContext<'ll, 'tcx> {
671        self.coverage_cx.as_ref().expect("only called when coverage instrumentation is enabled")
672    }
673
674    pub(crate) fn create_used_variable_impl(&self, name: &'static CStr, values: &[&'ll Value]) {
675        let array = self.const_array(self.type_ptr(), values);
676
677        let g = llvm::add_global(self.llmod, self.val_ty(array), name);
678        llvm::set_initializer(g, array);
679        llvm::set_linkage(g, llvm::Linkage::AppendingLinkage);
680        llvm::set_section(g, c"llvm.metadata");
681    }
682}
683impl<'ll> SimpleCx<'ll> {
684    pub(crate) fn get_type_of_global(&self, val: &'ll Value) -> &'ll Type {
685        unsafe { llvm::LLVMGlobalGetValueType(val) }
686    }
687    pub(crate) fn val_ty(&self, v: &'ll Value) -> &'ll Type {
688        common::val_ty(v)
689    }
690}
691impl<'ll> SimpleCx<'ll> {
692    pub(crate) fn new(
693        llmod: &'ll llvm::Module,
694        llcx: &'ll llvm::Context,
695        pointer_size: Size,
696    ) -> Self {
697        let isize_ty = llvm::Type::ix_llcx(llcx, pointer_size.bits());
698        Self(SCx { llmod, llcx, isize_ty }, PhantomData)
699    }
700}
701
702impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
703    pub(crate) fn get_metadata_value(&self, metadata: &'ll Metadata) -> &'ll Value {
704        llvm::LLVMMetadataAsValue(self.llcx(), metadata)
705    }
706
707    pub(crate) fn get_const_int(&self, ty: &'ll Type, val: u64) -> &'ll Value {
708        unsafe { llvm::LLVMConstInt(ty, val, llvm::FALSE) }
709    }
710
711    pub(crate) fn get_const_i64(&self, n: u64) -> &'ll Value {
712        self.get_const_int(self.type_i64(), n)
713    }
714
715    pub(crate) fn get_const_i32(&self, n: u64) -> &'ll Value {
716        self.get_const_int(self.type_i32(), n)
717    }
718
719    pub(crate) fn get_const_i16(&self, n: u64) -> &'ll Value {
720        self.get_const_int(self.type_i16(), n)
721    }
722
723    pub(crate) fn get_const_i8(&self, n: u64) -> &'ll Value {
724        self.get_const_int(self.type_i8(), n)
725    }
726
727    pub(crate) fn get_function(&self, name: &str) -> Option<&'ll Value> {
728        let name = SmallCStr::new(name);
729        unsafe { llvm::LLVMGetNamedFunction((**self).borrow().llmod, name.as_ptr()) }
730    }
731
732    pub(crate) fn get_md_kind_id(&self, name: &str) -> llvm::MetadataKindId {
733        unsafe {
734            llvm::LLVMGetMDKindIDInContext(
735                self.llcx(),
736                name.as_ptr() as *const c_char,
737                name.len() as c_uint,
738            )
739        }
740    }
741
742    pub(crate) fn create_metadata(&self, name: &[u8]) -> &'ll Metadata {
743        unsafe {
744            llvm::LLVMMDStringInContext2(self.llcx(), name.as_ptr() as *const c_char, name.len())
745        }
746    }
747}
748
749impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
750    fn vtables(
751        &self,
752    ) -> &RefCell<FxHashMap<(Ty<'tcx>, Option<ty::ExistentialTraitRef<'tcx>>), &'ll Value>> {
753        &self.vtables
754    }
755
756    fn apply_vcall_visibility_metadata(
757        &self,
758        ty: Ty<'tcx>,
759        poly_trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
760        vtable: &'ll Value,
761    ) {
762        apply_vcall_visibility_metadata(self, ty, poly_trait_ref, vtable);
763    }
764
765    fn get_fn(&self, instance: Instance<'tcx>) -> &'ll Value {
766        get_fn(self, instance)
767    }
768
769    fn get_fn_addr(&self, instance: Instance<'tcx>) -> &'ll Value {
770        get_fn(self, instance)
771    }
772
773    fn eh_personality(&self) -> &'ll Value {
774        // The exception handling personality function.
775        //
776        // If our compilation unit has the `eh_personality` lang item somewhere
777        // within it, then we just need to codegen that. Otherwise, we're
778        // building an rlib which will depend on some upstream implementation of
779        // this function, so we just codegen a generic reference to it. We don't
780        // specify any of the types for the function, we just make it a symbol
781        // that LLVM can later use.
782        //
783        // Note that MSVC is a little special here in that we don't use the
784        // `eh_personality` lang item at all. Currently LLVM has support for
785        // both Dwarf and SEH unwind mechanisms for MSVC targets and uses the
786        // *name of the personality function* to decide what kind of unwind side
787        // tables/landing pads to emit. It looks like Dwarf is used by default,
788        // injecting a dependency on the `_Unwind_Resume` symbol for resuming
789        // an "exception", but for MSVC we want to force SEH. This means that we
790        // can't actually have the personality function be our standard
791        // `rust_eh_personality` function, but rather we wired it up to the
792        // CRT's custom personality function, which forces LLVM to consider
793        // landing pads as "landing pads for SEH".
794        if let Some(llpersonality) = self.eh_personality.get() {
795            return llpersonality;
796        }
797
798        let name = if wants_msvc_seh(self.sess()) {
799            Some("__CxxFrameHandler3")
800        } else if wants_wasm_eh(self.sess()) {
801            // LLVM specifically tests for the name of the personality function
802            // There is no need for this function to exist anywhere, it will
803            // not be called. However, its name has to be "__gxx_wasm_personality_v0"
804            // for native wasm exceptions.
805            Some("__gxx_wasm_personality_v0")
806        } else {
807            None
808        };
809
810        let tcx = self.tcx;
811        let llfn = match tcx.lang_items().eh_personality() {
812            Some(def_id) if name.is_none() => self.get_fn_addr(ty::Instance::expect_resolve(
813                tcx,
814                self.typing_env(),
815                def_id,
816                ty::List::empty(),
817                DUMMY_SP,
818            )),
819            _ => {
820                let name = name.unwrap_or("rust_eh_personality");
821                if let Some(llfn) = self.get_declared_value(name) {
822                    llfn
823                } else {
824                    let fty = self.type_variadic_func(&[], self.type_i32());
825                    let llfn = self.declare_cfn(name, llvm::UnnamedAddr::Global, fty);
826                    let target_cpu = attributes::target_cpu_attr(self);
827                    attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[target_cpu]);
828                    llfn
829                }
830            }
831        };
832        self.eh_personality.set(Some(llfn));
833        llfn
834    }
835
836    fn sess(&self) -> &Session {
837        self.tcx.sess
838    }
839
840    fn set_frame_pointer_type(&self, llfn: &'ll Value) {
841        if let Some(attr) = attributes::frame_pointer_type_attr(self) {
842            attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[attr]);
843        }
844    }
845
846    fn apply_target_cpu_attr(&self, llfn: &'ll Value) {
847        let mut attrs = SmallVec::<[_; 2]>::new();
848        attrs.push(attributes::target_cpu_attr(self));
849        attrs.extend(attributes::tune_cpu_attr(self));
850        attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &attrs);
851    }
852
853    fn declare_c_main(&self, fn_type: Self::Type) -> Option<Self::Function> {
854        let entry_name = self.sess().target.entry_name.as_ref();
855        if self.get_declared_value(entry_name).is_none() {
856            let llfn = self.declare_entry_fn(
857                entry_name,
858                llvm::CallConv::from_conv(
859                    self.sess().target.entry_abi,
860                    self.sess().target.arch.borrow(),
861                ),
862                llvm::UnnamedAddr::Global,
863                fn_type,
864            );
865            attributes::apply_to_llfn(
866                llfn,
867                llvm::AttributePlace::Function,
868                attributes::target_features_attr(self, vec![]).as_slice(),
869            );
870            Some(llfn)
871        } else {
872            // If the symbol already exists, it is an error: for example, the user wrote
873            // #[no_mangle] extern "C" fn main(..) {..}
874            None
875        }
876    }
877}
878
879impl<'ll> CodegenCx<'ll, '_> {
880    pub(crate) fn get_intrinsic(
881        &self,
882        base_name: Cow<'static, str>,
883        type_params: &[&'ll Type],
884    ) -> (&'ll Type, &'ll Value) {
885        *self
886            .intrinsics
887            .borrow_mut()
888            .entry((base_name, SmallVec::from_slice(type_params)))
889            .or_insert_with_key(|(base_name, type_params)| {
890                self.declare_intrinsic(base_name, type_params)
891            })
892    }
893
894    fn declare_intrinsic(
895        &self,
896        base_name: &str,
897        type_params: &[&'ll Type],
898    ) -> (&'ll Type, &'ll Value) {
899        // This isn't an "LLVM intrinsic", but LLVM's optimization passes
900        // recognize it like one (including turning it into `bcmp` sometimes)
901        // and we use it to implement intrinsics like `raw_eq` and `compare_bytes`
902        if base_name == "memcmp" {
903            let fn_ty = self
904                .type_func(&[self.type_ptr(), self.type_ptr(), self.type_isize()], self.type_int());
905            let f = self.declare_cfn("memcmp", llvm::UnnamedAddr::No, fn_ty);
906
907            return (fn_ty, f);
908        }
909
910        let intrinsic = llvm::Intrinsic::lookup(base_name.as_bytes())
911            .unwrap_or_else(|| bug!("Unknown intrinsic: `{base_name}`"));
912        let f = intrinsic.get_declaration(self.llmod, &type_params);
913
914        (self.get_type_of_global(f), f)
915    }
916
917    pub(crate) fn eh_catch_typeinfo(&self) -> &'ll Value {
918        if let Some(eh_catch_typeinfo) = self.eh_catch_typeinfo.get() {
919            return eh_catch_typeinfo;
920        }
921        let tcx = self.tcx;
922        assert!(self.sess().target.os == "emscripten");
923        let eh_catch_typeinfo = match tcx.lang_items().eh_catch_typeinfo() {
924            Some(def_id) => self.get_static(def_id),
925            _ => {
926                let ty = self.type_struct(&[self.type_ptr(), self.type_ptr()], false);
927                self.declare_global(&mangle_internal_symbol(self.tcx, "rust_eh_catch_typeinfo"), ty)
928            }
929        };
930        self.eh_catch_typeinfo.set(Some(eh_catch_typeinfo));
931        eh_catch_typeinfo
932    }
933}
934
935impl CodegenCx<'_, '_> {
936    /// Generates a new symbol name with the given prefix. This symbol name must
937    /// only be used for definitions with `internal` or `private` linkage.
938    pub(crate) fn generate_local_symbol_name(&self, prefix: &str) -> String {
939        let idx = self.local_gen_sym_counter.get();
940        self.local_gen_sym_counter.set(idx + 1);
941        // Include a '.' character, so there can be no accidental conflicts with
942        // user defined names
943        let mut name = String::with_capacity(prefix.len() + 6);
944        name.push_str(prefix);
945        name.push('.');
946        name.push_str(&(idx as u64).to_base(ALPHANUMERIC_ONLY));
947        name
948    }
949}
950
951impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
952    /// A wrapper for [`llvm::LLVMSetMetadata`], but it takes `Metadata` as a parameter instead of `Value`.
953    pub(crate) fn set_metadata<'a>(
954        &self,
955        val: &'a Value,
956        kind_id: impl Into<llvm::MetadataKindId>,
957        md: &'ll Metadata,
958    ) {
959        let node = self.get_metadata_value(md);
960        llvm::LLVMSetMetadata(val, kind_id.into(), node);
961    }
962}
963
964impl HasDataLayout for CodegenCx<'_, '_> {
965    #[inline]
966    fn data_layout(&self) -> &TargetDataLayout {
967        &self.tcx.data_layout
968    }
969}
970
971impl HasTargetSpec for CodegenCx<'_, '_> {
972    #[inline]
973    fn target_spec(&self) -> &Target {
974        &self.tcx.sess.target
975    }
976}
977
978impl<'tcx> ty::layout::HasTyCtxt<'tcx> for CodegenCx<'_, 'tcx> {
979    #[inline]
980    fn tcx(&self) -> TyCtxt<'tcx> {
981        self.tcx
982    }
983}
984
985impl<'tcx, 'll> HasTypingEnv<'tcx> for CodegenCx<'ll, 'tcx> {
986    fn typing_env(&self) -> ty::TypingEnv<'tcx> {
987        ty::TypingEnv::fully_monomorphized()
988    }
989}
990
991impl<'tcx> LayoutOfHelpers<'tcx> for CodegenCx<'_, 'tcx> {
992    #[inline]
993    fn handle_layout_err(&self, err: LayoutError<'tcx>, span: Span, ty: Ty<'tcx>) -> ! {
994        if let LayoutError::SizeOverflow(_) | LayoutError::ReferencesError(_) = err {
995            self.tcx.dcx().emit_fatal(Spanned { span, node: err.into_diagnostic() })
996        } else {
997            self.tcx.dcx().emit_fatal(ssa_errors::FailedToGetLayout { span, ty, err })
998        }
999    }
1000}
1001
1002impl<'tcx> FnAbiOfHelpers<'tcx> for CodegenCx<'_, 'tcx> {
1003    #[inline]
1004    fn handle_fn_abi_err(
1005        &self,
1006        err: FnAbiError<'tcx>,
1007        span: Span,
1008        fn_abi_request: FnAbiRequest<'tcx>,
1009    ) -> ! {
1010        match err {
1011            FnAbiError::Layout(LayoutError::SizeOverflow(_) | LayoutError::Cycle(_)) => {
1012                self.tcx.dcx().emit_fatal(Spanned { span, node: err });
1013            }
1014            _ => match fn_abi_request {
1015                FnAbiRequest::OfFnPtr { sig, extra_args } => {
1016                    span_bug!(span, "`fn_abi_of_fn_ptr({sig}, {extra_args:?})` failed: {err:?}",);
1017                }
1018                FnAbiRequest::OfInstance { instance, extra_args } => {
1019                    span_bug!(
1020                        span,
1021                        "`fn_abi_of_instance({instance}, {extra_args:?})` failed: {err:?}",
1022                    );
1023                }
1024            },
1025        }
1026    }
1027}
rustc_codegen_llvm/context.rs

rustc_codegen_llvm/
context.rs
