rustc_codegen_llvm/
attributes.rs

1//! Set and unset common attributes on LLVM values.
2use rustc_hir::attrs::{InlineAttr, InstructionSetAttr, OptimizeAttr, RtsanSetting};
3use rustc_hir::def_id::DefId;
4use rustc_hir::find_attr;
5use rustc_middle::middle::codegen_fn_attrs::{
6    CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry, SanitizerFnAttrs,
7};
8use rustc_middle::ty::{self, TyCtxt};
9use rustc_session::config::{BranchProtection, FunctionReturn, OptLevel, PAuthKey, PacRet};
10use rustc_symbol_mangling::mangle_internal_symbol;
11use rustc_target::spec::{Arch, FramePointer, SanitizerSet, StackProbeType, StackProtector};
12use smallvec::SmallVec;
13
14use crate::context::SimpleCx;
15use crate::errors::SanitizerMemtagRequiresMte;
16use crate::llvm::AttributePlace::Function;
17use crate::llvm::{
18    self, AllocKindFlags, Attribute, AttributeKind, AttributePlace, MemoryEffects, Value,
19};
20use crate::{Session, attributes, llvm_util};
21
22pub(crate) fn apply_to_llfn(llfn: &Value, idx: AttributePlace, attrs: &[&Attribute]) {
23    if !attrs.is_empty() {
24        llvm::AddFunctionAttributes(llfn, idx, attrs);
25    }
26}
27
28pub(crate) fn apply_to_callsite(callsite: &Value, idx: AttributePlace, attrs: &[&Attribute]) {
29    if !attrs.is_empty() {
30        llvm::AddCallSiteAttributes(callsite, idx, attrs);
31    }
32}
33
34pub(crate) fn has_string_attr(llfn: &Value, name: &str) -> bool {
35    llvm::HasStringAttribute(llfn, name)
36}
37
38pub(crate) fn remove_string_attr_from_llfn(llfn: &Value, name: &str) {
39    llvm::RemoveStringAttrFromFn(llfn, name);
40}
41
42/// Get LLVM attribute for the provided inline heuristic.
43pub(crate) fn inline_attr<'ll, 'tcx>(
44    cx: &SimpleCx<'ll>,
45    tcx: TyCtxt<'tcx>,
46    instance: ty::Instance<'tcx>,
47) -> Option<&'ll Attribute> {
48    // `optnone` requires `noinline`
49    let codegen_fn_attrs = tcx.codegen_fn_attrs(instance.def_id());
50    let inline = match (codegen_fn_attrs.inline, &codegen_fn_attrs.optimize) {
51        (_, OptimizeAttr::DoNotOptimize) => InlineAttr::Never,
52        (InlineAttr::None, _) if instance.def.requires_inline(tcx) => InlineAttr::Hint,
53        (inline, _) => inline,
54    };
55
56    if !tcx.sess.opts.unstable_opts.inline_llvm {
57        // disable LLVM inlining
58        return Some(AttributeKind::NoInline.create_attr(cx.llcx));
59    }
60    match inline {
61        InlineAttr::Hint => Some(AttributeKind::InlineHint.create_attr(cx.llcx)),
62        InlineAttr::Always | InlineAttr::Force { .. } => {
63            Some(AttributeKind::AlwaysInline.create_attr(cx.llcx))
64        }
65        InlineAttr::Never => {
66            if tcx.sess.target.arch != Arch::AmdGpu {
67                Some(AttributeKind::NoInline.create_attr(cx.llcx))
68            } else {
69                None
70            }
71        }
72        InlineAttr::None => None,
73    }
74}
75
76#[inline]
77fn patchable_function_entry_attrs<'ll>(
78    cx: &SimpleCx<'ll>,
79    sess: &Session,
80    attr: Option<PatchableFunctionEntry>,
81) -> SmallVec<[&'ll Attribute; 2]> {
82    let mut attrs = SmallVec::new();
83    let patchable_spec = attr.unwrap_or_else(|| {
84        PatchableFunctionEntry::from_config(sess.opts.unstable_opts.patchable_function_entry)
85    });
86    let entry = patchable_spec.entry();
87    let prefix = patchable_spec.prefix();
88    if entry > 0 {
89        attrs.push(llvm::CreateAttrStringValue(
90            cx.llcx,
91            "patchable-function-entry",
92            &::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("{0}", entry))
    })format!("{}", entry),
93        ));
94    }
95    if prefix > 0 {
96        attrs.push(llvm::CreateAttrStringValue(
97            cx.llcx,
98            "patchable-function-prefix",
99            &::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("{0}", prefix))
    })format!("{}", prefix),
100        ));
101    }
102    attrs
103}
104
105/// Get LLVM sanitize attributes.
106#[inline]
107pub(crate) fn sanitize_attrs<'ll, 'tcx>(
108    cx: &SimpleCx<'ll>,
109    tcx: TyCtxt<'tcx>,
110    sanitizer_fn_attr: SanitizerFnAttrs,
111) -> SmallVec<[&'ll Attribute; 4]> {
112    let mut attrs = SmallVec::new();
113    let enabled = tcx.sess.sanitizers() - sanitizer_fn_attr.disabled;
114    if enabled.contains(SanitizerSet::ADDRESS) || enabled.contains(SanitizerSet::KERNELADDRESS) {
115        attrs.push(llvm::AttributeKind::SanitizeAddress.create_attr(cx.llcx));
116    }
117    if enabled.contains(SanitizerSet::MEMORY) {
118        attrs.push(llvm::AttributeKind::SanitizeMemory.create_attr(cx.llcx));
119    }
120    if enabled.contains(SanitizerSet::THREAD) {
121        attrs.push(llvm::AttributeKind::SanitizeThread.create_attr(cx.llcx));
122    }
123    if enabled.contains(SanitizerSet::HWADDRESS) {
124        attrs.push(llvm::AttributeKind::SanitizeHWAddress.create_attr(cx.llcx));
125    }
126    if enabled.contains(SanitizerSet::SHADOWCALLSTACK) {
127        attrs.push(llvm::AttributeKind::ShadowCallStack.create_attr(cx.llcx));
128    }
129    if enabled.contains(SanitizerSet::MEMTAG) {
130        // Check to make sure the mte target feature is actually enabled.
131        let features = tcx.global_backend_features(());
132        let mte_feature =
133            features.iter().map(|s| &s[..]).rfind(|n| ["+mte", "-mte"].contains(&&n[..]));
134        if let None | Some("-mte") = mte_feature {
135            tcx.dcx().emit_err(SanitizerMemtagRequiresMte);
136        }
137
138        attrs.push(llvm::AttributeKind::SanitizeMemTag.create_attr(cx.llcx));
139    }
140    if enabled.contains(SanitizerSet::SAFESTACK) {
141        attrs.push(llvm::AttributeKind::SanitizeSafeStack.create_attr(cx.llcx));
142    }
143    if tcx.sess.sanitizers().contains(SanitizerSet::REALTIME) {
144        match sanitizer_fn_attr.rtsan_setting {
145            RtsanSetting::Nonblocking => {
146                attrs.push(llvm::AttributeKind::SanitizeRealtimeNonblocking.create_attr(cx.llcx))
147            }
148            RtsanSetting::Blocking => {
149                attrs.push(llvm::AttributeKind::SanitizeRealtimeBlocking.create_attr(cx.llcx))
150            }
151            // caller is the default, so no llvm attribute
152            RtsanSetting::Caller => (),
153        }
154    }
155    attrs
156}
157
158/// Tell LLVM to emit or not emit the information necessary to unwind the stack for the function.
159#[inline]
160pub(crate) fn uwtable_attr(llcx: &llvm::Context, use_sync_unwind: Option<bool>) -> &Attribute {
161    // NOTE: We should determine if we even need async unwind tables, as they
162    // take have more overhead and if we can use sync unwind tables we
163    // probably should.
164    let async_unwind = !use_sync_unwind.unwrap_or(false);
165    llvm::CreateUWTableAttr(llcx, async_unwind)
166}
167
168pub(crate) fn frame_pointer_type_attr<'ll>(
169    cx: &SimpleCx<'ll>,
170    sess: &Session,
171) -> Option<&'ll Attribute> {
172    let mut fp = sess.target.frame_pointer;
173    let opts = &sess.opts;
174    // "mcount" function relies on stack pointer.
175    // See <https://sourceware.org/binutils/docs/gprof/Implementation.html>.
176    if opts.unstable_opts.instrument_mcount {
177        fp.ratchet(FramePointer::Always);
178    }
179    fp.ratchet(opts.cg.force_frame_pointers);
180    let attr_value = match fp {
181        FramePointer::Always => "all",
182        FramePointer::NonLeaf => "non-leaf",
183        FramePointer::MayOmit => return None,
184    };
185    Some(llvm::CreateAttrStringValue(cx.llcx, "frame-pointer", attr_value))
186}
187
188fn function_return_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
189    let function_return_attr = match sess.opts.unstable_opts.function_return {
190        FunctionReturn::Keep => return None,
191        FunctionReturn::ThunkExtern => AttributeKind::FnRetThunkExtern,
192    };
193
194    Some(function_return_attr.create_attr(cx.llcx))
195}
196
197/// Tell LLVM what instrument function to insert.
198#[inline]
199fn instrument_function_attr<'ll>(
200    cx: &SimpleCx<'ll>,
201    sess: &Session,
202) -> SmallVec<[&'ll Attribute; 4]> {
203    let mut attrs = SmallVec::new();
204    if sess.opts.unstable_opts.instrument_mcount {
205        // Similar to `clang -pg` behavior. Handled by the
206        // `post-inline-ee-instrument` LLVM pass.
207
208        // The function name varies on platforms.
209        // See test/CodeGen/mcount.c in clang.
210        let mcount_name = match &sess.target.llvm_mcount_intrinsic {
211            Some(llvm_mcount_intrinsic) => llvm_mcount_intrinsic.as_ref(),
212            None => sess.target.mcount.as_ref(),
213        };
214
215        attrs.push(llvm::CreateAttrStringValue(
216            cx.llcx,
217            "instrument-function-entry-inlined",
218            mcount_name,
219        ));
220    }
221    if let Some(options) = &sess.opts.unstable_opts.instrument_xray {
222        // XRay instrumentation is similar to __cyg_profile_func_{enter,exit}.
223        // Function prologue and epilogue are instrumented with NOP sleds,
224        // a runtime library later replaces them with detours into tracing code.
225        if options.always {
226            attrs.push(llvm::CreateAttrStringValue(cx.llcx, "function-instrument", "xray-always"));
227        }
228        if options.never {
229            attrs.push(llvm::CreateAttrStringValue(cx.llcx, "function-instrument", "xray-never"));
230        }
231        if options.ignore_loops {
232            attrs.push(llvm::CreateAttrString(cx.llcx, "xray-ignore-loops"));
233        }
234        // LLVM will not choose the default for us, but rather requires specific
235        // threshold in absence of "xray-always". Use the same default as Clang.
236        let threshold = options.instruction_threshold.unwrap_or(200);
237        attrs.push(llvm::CreateAttrStringValue(
238            cx.llcx,
239            "xray-instruction-threshold",
240            &threshold.to_string(),
241        ));
242        if options.skip_entry {
243            attrs.push(llvm::CreateAttrString(cx.llcx, "xray-skip-entry"));
244        }
245        if options.skip_exit {
246            attrs.push(llvm::CreateAttrString(cx.llcx, "xray-skip-exit"));
247        }
248    }
249    attrs
250}
251
252fn nojumptables_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
253    if sess.opts.cg.jump_tables {
254        return None;
255    }
256
257    Some(llvm::CreateAttrStringValue(cx.llcx, "no-jump-tables", "true"))
258}
259
260fn probestack_attr<'ll, 'tcx>(cx: &SimpleCx<'ll>, tcx: TyCtxt<'tcx>) -> Option<&'ll Attribute> {
261    // Currently stack probes seem somewhat incompatible with the address
262    // sanitizer and thread sanitizer. With asan we're already protected from
263    // stack overflow anyway so we don't really need stack probes regardless.
264    if tcx.sess.sanitizers().intersects(SanitizerSet::ADDRESS | SanitizerSet::THREAD) {
265        return None;
266    }
267
268    // probestack doesn't play nice either with `-C profile-generate`.
269    if tcx.sess.opts.cg.profile_generate.enabled() {
270        return None;
271    }
272
273    let attr_value = match tcx.sess.target.stack_probes {
274        StackProbeType::None => return None,
275        // Request LLVM to generate the probes inline. If the given LLVM version does not support
276        // this, no probe is generated at all (even if the attribute is specified).
277        StackProbeType::Inline => "inline-asm",
278        // Flag our internal `__rust_probestack` function as the stack probe symbol.
279        // This is defined in the `compiler-builtins` crate for each architecture.
280        StackProbeType::Call => &mangle_internal_symbol(tcx, "__rust_probestack"),
281        // Pick from the two above based on the LLVM version.
282        StackProbeType::InlineOrCall { min_llvm_version_for_inline } => {
283            if llvm_util::get_version() < min_llvm_version_for_inline {
284                &mangle_internal_symbol(tcx, "__rust_probestack")
285            } else {
286                "inline-asm"
287            }
288        }
289    };
290    Some(llvm::CreateAttrStringValue(cx.llcx, "probe-stack", attr_value))
291}
292
293fn stackprotector_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
294    let sspattr = match sess.stack_protector() {
295        StackProtector::None => return None,
296        StackProtector::All => AttributeKind::StackProtectReq,
297        StackProtector::Strong => AttributeKind::StackProtectStrong,
298        StackProtector::Basic => AttributeKind::StackProtect,
299    };
300
301    Some(sspattr.create_attr(cx.llcx))
302}
303
304pub(crate) fn target_cpu_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> &'ll Attribute {
305    let target_cpu = llvm_util::target_cpu(sess);
306    llvm::CreateAttrStringValue(cx.llcx, "target-cpu", target_cpu)
307}
308
309pub(crate) fn tune_cpu_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
310    llvm_util::tune_cpu(sess)
311        .map(|tune_cpu| llvm::CreateAttrStringValue(cx.llcx, "tune-cpu", tune_cpu))
312}
313
314/// Get the `target-features` LLVM attribute.
315pub(crate) fn target_features_attr<'ll, 'tcx>(
316    cx: &SimpleCx<'ll>,
317    tcx: TyCtxt<'tcx>,
318    function_features: Vec<String>,
319) -> Option<&'ll Attribute> {
320    let global_features = tcx.global_backend_features(()).iter().map(String::as_str);
321    let function_features = function_features.iter().map(String::as_str);
322    let target_features =
323        global_features.chain(function_features).intersperse(",").collect::<String>();
324    (!target_features.is_empty())
325        .then(|| llvm::CreateAttrStringValue(cx.llcx, "target-features", &target_features))
326}
327
328/// Get the `NonLazyBind` LLVM attribute,
329/// if the codegen options allow skipping the PLT.
330pub(crate) fn non_lazy_bind_attr<'ll>(
331    cx: &SimpleCx<'ll>,
332    sess: &Session,
333) -> Option<&'ll Attribute> {
334    // Don't generate calls through PLT if it's not necessary
335    if !sess.needs_plt() { Some(AttributeKind::NonLazyBind.create_attr(cx.llcx)) } else { None }
336}
337
338/// Get the default optimizations attrs for a function.
339#[inline]
340pub(crate) fn default_optimisation_attrs<'ll>(
341    cx: &SimpleCx<'ll>,
342    sess: &Session,
343) -> SmallVec<[&'ll Attribute; 2]> {
344    let mut attrs = SmallVec::new();
345    match sess.opts.optimize {
346        OptLevel::Size => {
347            attrs.push(llvm::AttributeKind::OptimizeForSize.create_attr(cx.llcx));
348        }
349        OptLevel::SizeMin => {
350            attrs.push(llvm::AttributeKind::MinSize.create_attr(cx.llcx));
351            attrs.push(llvm::AttributeKind::OptimizeForSize.create_attr(cx.llcx));
352        }
353        _ => {}
354    }
355    attrs
356}
357
358fn create_alloc_family_attr(llcx: &llvm::Context) -> &llvm::Attribute {
359    llvm::CreateAttrStringValue(llcx, "alloc-family", "__rust_alloc")
360}
361
362/// Helper for `FnAbiLlvmExt::apply_attrs_llfn`:
363/// Composite function which sets LLVM attributes for function depending on its AST (`#[attribute]`)
364/// attributes.
365pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
366    cx: &SimpleCx<'ll>,
367    tcx: TyCtxt<'tcx>,
368    llfn: &'ll Value,
369    codegen_fn_attrs: &CodegenFnAttrs,
370    instance: Option<ty::Instance<'tcx>>,
371) {
372    let sess = tcx.sess;
373    let mut to_add = SmallVec::<[_; 16]>::new();
374
375    match codegen_fn_attrs.optimize {
376        OptimizeAttr::Default => {
377            to_add.extend(default_optimisation_attrs(cx, sess));
378        }
379        OptimizeAttr::DoNotOptimize => {
380            to_add.push(llvm::AttributeKind::OptimizeNone.create_attr(cx.llcx));
381        }
382        OptimizeAttr::Size => {
383            to_add.push(llvm::AttributeKind::MinSize.create_attr(cx.llcx));
384            to_add.push(llvm::AttributeKind::OptimizeForSize.create_attr(cx.llcx));
385        }
386        OptimizeAttr::Speed => {}
387    }
388
389    if sess.must_emit_unwind_tables() {
390        to_add.push(uwtable_attr(cx.llcx, sess.opts.unstable_opts.use_sync_unwind));
391    }
392
393    if sess.opts.unstable_opts.profile_sample_use.is_some() {
394        to_add.push(llvm::CreateAttrString(cx.llcx, "use-sample-profile"));
395    }
396
397    // FIXME: none of these functions interact with source level attributes.
398    to_add.extend(frame_pointer_type_attr(cx, sess));
399    to_add.extend(function_return_attr(cx, sess));
400    to_add.extend(instrument_function_attr(cx, sess));
401    to_add.extend(nojumptables_attr(cx, sess));
402    to_add.extend(probestack_attr(cx, tcx));
403    to_add.extend(stackprotector_attr(cx, sess));
404
405    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NO_BUILTINS) {
406        to_add.push(llvm::CreateAttrString(cx.llcx, "no-builtins"));
407    }
408
409    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::OFFLOAD_KERNEL) {
410        to_add.push(llvm::CreateAttrString(cx.llcx, "offload-kernel"))
411    }
412
413    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::COLD) {
414        to_add.push(AttributeKind::Cold.create_attr(cx.llcx));
415    }
416    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::FFI_PURE) {
417        to_add.push(MemoryEffects::ReadOnly.create_attr(cx.llcx));
418    }
419    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::FFI_CONST) {
420        to_add.push(MemoryEffects::None.create_attr(cx.llcx));
421    }
422    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NAKED) {
423        // do nothing; a naked function is converted into an extern function
424        // and a global assembly block. LLVM's support for naked functions is
425        // not used.
426    } else {
427        // Do not set sanitizer attributes for naked functions.
428        to_add.extend(sanitize_attrs(cx, tcx, codegen_fn_attrs.sanitizers));
429
430        // For non-naked functions, set branch protection attributes on aarch64.
431        if let Some(BranchProtection { bti, pac_ret, gcs }) =
432            sess.opts.unstable_opts.branch_protection
433        {
434            if !(sess.target.arch == Arch::AArch64) {
    ::core::panicking::panic("assertion failed: sess.target.arch == Arch::AArch64")
};assert!(sess.target.arch == Arch::AArch64);
435            if bti {
436                to_add.push(llvm::CreateAttrString(cx.llcx, "branch-target-enforcement"));
437            }
438            if gcs {
439                to_add.push(llvm::CreateAttrString(cx.llcx, "guarded-control-stack"));
440            }
441            if let Some(PacRet { leaf, pc, key }) = pac_ret {
442                if pc {
443                    to_add.push(llvm::CreateAttrString(cx.llcx, "branch-protection-pauth-lr"));
444                }
445                to_add.push(llvm::CreateAttrStringValue(
446                    cx.llcx,
447                    "sign-return-address",
448                    if leaf { "all" } else { "non-leaf" },
449                ));
450                to_add.push(llvm::CreateAttrStringValue(
451                    cx.llcx,
452                    "sign-return-address-key",
453                    if key == PAuthKey::A { "a_key" } else { "b_key" },
454                ));
455            }
456        }
457    }
458    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR)
459        || codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR_ZEROED)
460    {
461        to_add.push(create_alloc_family_attr(cx.llcx));
462        if let Some(instance) = instance
463            && let Some(name) = {
    'done:
        {
        for i in tcx.get_all_attrs(instance.def_id()) {
            let i: &rustc_hir::Attribute = i;
            match i {
                rustc_hir::Attribute::Parsed(rustc_hir::attrs::AttributeKind::RustcAllocatorZeroedVariant {
                    name }) => {
                    break 'done Some(name);
                }
                _ => {}
            }
        }
        None
    }
}find_attr!(tcx.get_all_attrs(instance.def_id()), rustc_hir::attrs::AttributeKind::RustcAllocatorZeroedVariant {name} => name)
464        {
465            to_add.push(llvm::CreateAttrStringValue(
466                cx.llcx,
467                "alloc-variant-zeroed",
468                &mangle_internal_symbol(tcx, name.as_str()),
469            ));
470        }
471        // apply to argument place instead of function
472        let alloc_align = AttributeKind::AllocAlign.create_attr(cx.llcx);
473        attributes::apply_to_llfn(llfn, AttributePlace::Argument(1), &[alloc_align]);
474        to_add.push(llvm::CreateAllocSizeAttr(cx.llcx, 0));
475        let mut flags = AllocKindFlags::Alloc | AllocKindFlags::Aligned;
476        if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR) {
477            flags |= AllocKindFlags::Uninitialized;
478        } else {
479            flags |= AllocKindFlags::Zeroed;
480        }
481        to_add.push(llvm::CreateAllocKindAttr(cx.llcx, flags));
482        // apply to return place instead of function (unlike all other attributes applied in this
483        // function)
484        let no_alias = AttributeKind::NoAlias.create_attr(cx.llcx);
485        attributes::apply_to_llfn(llfn, AttributePlace::ReturnValue, &[no_alias]);
486    }
487    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::REALLOCATOR) {
488        to_add.push(create_alloc_family_attr(cx.llcx));
489        to_add.push(llvm::CreateAllocKindAttr(
490            cx.llcx,
491            AllocKindFlags::Realloc | AllocKindFlags::Aligned,
492        ));
493        // applies to argument place instead of function place
494        let allocated_pointer = AttributeKind::AllocatedPointer.create_attr(cx.llcx);
495        attributes::apply_to_llfn(llfn, AttributePlace::Argument(0), &[allocated_pointer]);
496        // apply to argument place instead of function
497        let alloc_align = AttributeKind::AllocAlign.create_attr(cx.llcx);
498        attributes::apply_to_llfn(llfn, AttributePlace::Argument(2), &[alloc_align]);
499        to_add.push(llvm::CreateAllocSizeAttr(cx.llcx, 3));
500        let no_alias = AttributeKind::NoAlias.create_attr(cx.llcx);
501        attributes::apply_to_llfn(llfn, AttributePlace::ReturnValue, &[no_alias]);
502    }
503    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::DEALLOCATOR) {
504        to_add.push(create_alloc_family_attr(cx.llcx));
505        to_add.push(llvm::CreateAllocKindAttr(cx.llcx, AllocKindFlags::Free));
506        // applies to argument place instead of function place
507        let allocated_pointer = AttributeKind::AllocatedPointer.create_attr(cx.llcx);
508        let attrs: &[_] = if llvm_util::get_version() >= (21, 0, 0) {
509            // "Does not capture provenance" means "if the function call stashes the pointer somewhere,
510            // accessing that pointer after the function returns is UB". That is definitely the case here since
511            // freeing will destroy the provenance.
512            let captures_addr = AttributeKind::CapturesAddress.create_attr(cx.llcx);
513            &[allocated_pointer, captures_addr]
514        } else {
515            &[allocated_pointer]
516        };
517        attributes::apply_to_llfn(llfn, AttributePlace::Argument(0), attrs);
518    }
519    if let Some(align) = codegen_fn_attrs.alignment {
520        llvm::set_alignment(llfn, align);
521    }
522    to_add.extend(patchable_function_entry_attrs(
523        cx,
524        sess,
525        codegen_fn_attrs.patchable_function_entry,
526    ));
527
528    // Always annotate functions with the target-cpu they are compiled for.
529    // Without this, ThinLTO won't inline Rust functions into Clang generated
530    // functions (because Clang annotates functions this way too).
531    to_add.push(target_cpu_attr(cx, sess));
532    // tune-cpu is only conveyed through the attribute for our purpose.
533    // The target doesn't care; the subtarget reads our attribute.
534    to_add.extend(tune_cpu_attr(cx, sess));
535
536    let function_features =
537        codegen_fn_attrs.target_features.iter().map(|f| f.name.as_str()).collect::<Vec<&str>>();
538
539    // Apply function attributes as per usual if there are no user defined
540    // target features otherwise this will get applied at the callsite.
541    if function_features.is_empty() {
542        if let Some(instance) = instance
543            && let Some(inline_attr) = inline_attr(cx, tcx, instance)
544        {
545            to_add.push(inline_attr);
546        }
547    }
548
549    let function_features = function_features
550        .iter()
551        // Convert to LLVMFeatures and filter out unavailable ones
552        .flat_map(|feat| llvm_util::to_llvm_features(sess, feat))
553        // Convert LLVMFeatures & dependencies to +<feats>s
554        .flat_map(|feat| feat.into_iter().map(|f| ::alloc::__export::must_use({ ::alloc::fmt::format(format_args!("+{0}", f)) })format!("+{f}")))
555        .chain(codegen_fn_attrs.instruction_set.iter().map(|x| match x {
556            InstructionSetAttr::ArmA32 => "-thumb-mode".to_string(),
557            InstructionSetAttr::ArmT32 => "+thumb-mode".to_string(),
558        }))
559        .collect::<Vec<String>>();
560
561    if sess.target.is_like_wasm {
562        // If this function is an import from the environment but the wasm
563        // import has a specific module/name, apply them here.
564        if let Some(instance) = instance
565            && let Some(module) = wasm_import_module(tcx, instance.def_id())
566        {
567            to_add.push(llvm::CreateAttrStringValue(cx.llcx, "wasm-import-module", module));
568
569            let name =
570                codegen_fn_attrs.symbol_name.unwrap_or_else(|| tcx.item_name(instance.def_id()));
571            let name = name.as_str();
572            to_add.push(llvm::CreateAttrStringValue(cx.llcx, "wasm-import-name", name));
573        }
574    }
575
576    to_add.extend(target_features_attr(cx, tcx, function_features));
577
578    attributes::apply_to_llfn(llfn, Function, &to_add);
579}
580
581fn wasm_import_module(tcx: TyCtxt<'_>, id: DefId) -> Option<&String> {
582    tcx.wasm_import_module_map(id.krate).get(&id)
583}
rustc_codegen_llvm/attributes.rs

rustc_codegen_llvm/
attributes.rs
