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