rustc_codegen_llvm/
abi.rs

1use std::cmp;
2
3use libc::c_uint;
4use rustc_abi::{
5    ArmCall, BackendRepr, CanonAbi, HasDataLayout, InterruptKind, Primitive, Reg, RegKind, Size,
6    X86Call,
7};
8use rustc_codegen_ssa::MemFlags;
9use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
10use rustc_codegen_ssa::mir::place::{PlaceRef, PlaceValue};
11use rustc_codegen_ssa::traits::*;
12use rustc_middle::ty::Ty;
13use rustc_middle::ty::layout::LayoutOf;
14use rustc_middle::{bug, ty};
15use rustc_session::{Session, config};
16use rustc_target::callconv::{
17    ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, CastTarget, FnAbi, PassMode,
18};
19use rustc_target::spec::{Arch, SanitizerSet};
20use smallvec::SmallVec;
21
22use crate::attributes::{self, llfn_attrs_from_instance};
23use crate::builder::Builder;
24use crate::context::CodegenCx;
25use crate::llvm::{self, Attribute, AttributePlace, Type, Value};
26use crate::llvm_util;
27use crate::type_of::LayoutLlvmExt;
28
29trait ArgAttributesExt {
30    fn apply_attrs_to_llfn(&self, idx: AttributePlace, cx: &CodegenCx<'_, '_>, llfn: &Value);
31    fn apply_attrs_to_callsite(
32        &self,
33        idx: AttributePlace,
34        cx: &CodegenCx<'_, '_>,
35        callsite: &Value,
36    );
37}
38
39const ABI_AFFECTING_ATTRIBUTES: [(ArgAttribute, llvm::AttributeKind); 1] =
40    [(ArgAttribute::InReg, llvm::AttributeKind::InReg)];
41
42const OPTIMIZATION_ATTRIBUTES: [(ArgAttribute, llvm::AttributeKind); 4] = [
43    (ArgAttribute::NoAlias, llvm::AttributeKind::NoAlias),
44    (ArgAttribute::NonNull, llvm::AttributeKind::NonNull),
45    (ArgAttribute::ReadOnly, llvm::AttributeKind::ReadOnly),
46    (ArgAttribute::NoUndef, llvm::AttributeKind::NoUndef),
47];
48
49fn get_attrs<'ll>(this: &ArgAttributes, cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'ll Attribute; 8]> {
50    let mut regular = this.regular;
51
52    let mut attrs = SmallVec::new();
53
54    // ABI-affecting attributes must always be applied
55    for (attr, llattr) in ABI_AFFECTING_ATTRIBUTES {
56        if regular.contains(attr) {
57            attrs.push(llattr.create_attr(cx.llcx));
58        }
59    }
60    if let Some(align) = this.pointee_align {
61        attrs.push(llvm::CreateAlignmentAttr(cx.llcx, align.bytes()));
62    }
63    match this.arg_ext {
64        ArgExtension::None => {}
65        ArgExtension::Zext => attrs.push(llvm::AttributeKind::ZExt.create_attr(cx.llcx)),
66        ArgExtension::Sext => attrs.push(llvm::AttributeKind::SExt.create_attr(cx.llcx)),
67    }
68
69    // Only apply remaining attributes when optimizing
70    if cx.sess().opts.optimize != config::OptLevel::No {
71        let deref = this.pointee_size.bytes();
72        if deref != 0 {
73            if regular.contains(ArgAttribute::NonNull) {
74                attrs.push(llvm::CreateDereferenceableAttr(cx.llcx, deref));
75            } else {
76                attrs.push(llvm::CreateDereferenceableOrNullAttr(cx.llcx, deref));
77            }
78            regular -= ArgAttribute::NonNull;
79        }
80        for (attr, llattr) in OPTIMIZATION_ATTRIBUTES {
81            if regular.contains(attr) {
82                attrs.push(llattr.create_attr(cx.llcx));
83            }
84        }
85        // captures(...) is only available since LLVM 21.
86        if (21, 0, 0) <= llvm_util::get_version() {
87            const CAPTURES_ATTRIBUTES: [(ArgAttribute, llvm::AttributeKind); 3] = [
88                (ArgAttribute::CapturesNone, llvm::AttributeKind::CapturesNone),
89                (ArgAttribute::CapturesAddress, llvm::AttributeKind::CapturesAddress),
90                (ArgAttribute::CapturesReadOnly, llvm::AttributeKind::CapturesReadOnly),
91            ];
92            for (attr, llattr) in CAPTURES_ATTRIBUTES {
93                if regular.contains(attr) {
94                    attrs.push(llattr.create_attr(cx.llcx));
95                    break;
96                }
97            }
98        }
99    } else if cx.tcx.sess.sanitizers().contains(SanitizerSet::MEMORY) {
100        // If we're not optimising, *but* memory sanitizer is on, emit noundef, since it affects
101        // memory sanitizer's behavior.
102
103        if regular.contains(ArgAttribute::NoUndef) {
104            attrs.push(llvm::AttributeKind::NoUndef.create_attr(cx.llcx));
105        }
106    }
107
108    attrs
109}
110
111impl ArgAttributesExt for ArgAttributes {
112    fn apply_attrs_to_llfn(&self, idx: AttributePlace, cx: &CodegenCx<'_, '_>, llfn: &Value) {
113        let attrs = get_attrs(self, cx);
114        attributes::apply_to_llfn(llfn, idx, &attrs);
115    }
116
117    fn apply_attrs_to_callsite(
118        &self,
119        idx: AttributePlace,
120        cx: &CodegenCx<'_, '_>,
121        callsite: &Value,
122    ) {
123        let attrs = get_attrs(self, cx);
124        attributes::apply_to_callsite(callsite, idx, &attrs);
125    }
126}
127
128pub(crate) trait LlvmType {
129    fn llvm_type<'ll>(&self, cx: &CodegenCx<'ll, '_>) -> &'ll Type;
130}
131
132impl LlvmType for Reg {
133    fn llvm_type<'ll>(&self, cx: &CodegenCx<'ll, '_>) -> &'ll Type {
134        match self.kind {
135            RegKind::Integer => cx.type_ix(self.size.bits()),
136            RegKind::Float => match self.size.bits() {
137                16 => cx.type_f16(),
138                32 => cx.type_f32(),
139                64 => cx.type_f64(),
140                128 => cx.type_f128(),
141                _ => bug!("unsupported float: {:?}", self),
142            },
143            RegKind::Vector => cx.type_vector(cx.type_i8(), self.size.bytes()),
144        }
145    }
146}
147
148impl LlvmType for CastTarget {
149    fn llvm_type<'ll>(&self, cx: &CodegenCx<'ll, '_>) -> &'ll Type {
150        let rest_ll_unit = self.rest.unit.llvm_type(cx);
151        let rest_count = if self.rest.total == Size::ZERO {
152            0
153        } else {
154            assert_ne!(
155                self.rest.unit.size,
156                Size::ZERO,
157                "total size {:?} cannot be divided into units of zero size",
158                self.rest.total
159            );
160            if !self.rest.total.bytes().is_multiple_of(self.rest.unit.size.bytes()) {
161                assert_eq!(self.rest.unit.kind, RegKind::Integer, "only int regs can be split");
162            }
163            self.rest.total.bytes().div_ceil(self.rest.unit.size.bytes())
164        };
165
166        // Simplify to a single unit or an array if there's no prefix.
167        // This produces the same layout, but using a simpler type.
168        if self.prefix.iter().all(|x| x.is_none()) {
169            // We can't do this if is_consecutive is set and the unit would get
170            // split on the target. Currently, this is only relevant for i128
171            // registers.
172            if rest_count == 1 && (!self.rest.is_consecutive || self.rest.unit != Reg::i128()) {
173                return rest_ll_unit;
174            }
175
176            return cx.type_array(rest_ll_unit, rest_count);
177        }
178
179        // Generate a struct type with the prefix and the "rest" arguments.
180        let prefix_args =
181            self.prefix.iter().flat_map(|option_reg| option_reg.map(|reg| reg.llvm_type(cx)));
182        let rest_args = (0..rest_count).map(|_| rest_ll_unit);
183        let args: Vec<_> = prefix_args.chain(rest_args).collect();
184        cx.type_struct(&args, false)
185    }
186}
187
188trait ArgAbiExt<'ll, 'tcx> {
189    fn store(
190        &self,
191        bx: &mut Builder<'_, 'll, 'tcx>,
192        val: &'ll Value,
193        dst: PlaceRef<'tcx, &'ll Value>,
194    );
195    fn store_fn_arg(
196        &self,
197        bx: &mut Builder<'_, 'll, 'tcx>,
198        idx: &mut usize,
199        dst: PlaceRef<'tcx, &'ll Value>,
200    );
201}
202
203impl<'ll, 'tcx> ArgAbiExt<'ll, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
204    /// Stores a direct/indirect value described by this ArgAbi into a
205    /// place for the original Rust type of this argument/return.
206    /// Can be used for both storing formal arguments into Rust variables
207    /// or results of call/invoke instructions into their destinations.
208    fn store(
209        &self,
210        bx: &mut Builder<'_, 'll, 'tcx>,
211        val: &'ll Value,
212        dst: PlaceRef<'tcx, &'ll Value>,
213    ) {
214        match &self.mode {
215            PassMode::Ignore => {}
216            // Sized indirect arguments
217            PassMode::Indirect { attrs, meta_attrs: None, on_stack: _ } => {
218                let align = attrs.pointee_align.unwrap_or(self.layout.align.abi);
219                OperandValue::Ref(PlaceValue::new_sized(val, align)).store(bx, dst);
220            }
221            // Unsized indirect arguments cannot be stored
222            PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
223                bug!("unsized `ArgAbi` cannot be stored");
224            }
225            PassMode::Cast { cast, pad_i32: _ } => {
226                // The ABI mandates that the value is passed as a different struct representation.
227                // Spill and reload it from the stack to convert from the ABI representation to
228                // the Rust representation.
229                let scratch_size = cast.size(bx);
230                let scratch_align = cast.align(bx);
231                // Note that the ABI type may be either larger or smaller than the Rust type,
232                // due to the presence or absence of trailing padding. For example:
233                // - On some ABIs, the Rust layout { f64, f32, <f32 padding> } may omit padding
234                //   when passed by value, making it smaller.
235                // - On some ABIs, the Rust layout { u16, u16, u16 } may be padded up to 8 bytes
236                //   when passed by value, making it larger.
237                let copy_bytes =
238                    cmp::min(cast.unaligned_size(bx).bytes(), self.layout.size.bytes());
239                // Allocate some scratch space...
240                let llscratch = bx.alloca(scratch_size, scratch_align);
241                bx.lifetime_start(llscratch, scratch_size);
242                // ...store the value...
243                rustc_codegen_ssa::mir::store_cast(bx, cast, val, llscratch, scratch_align);
244                // ... and then memcpy it to the intended destination.
245                bx.memcpy(
246                    dst.val.llval,
247                    self.layout.align.abi,
248                    llscratch,
249                    scratch_align,
250                    bx.const_usize(copy_bytes),
251                    MemFlags::empty(),
252                    None,
253                );
254                bx.lifetime_end(llscratch, scratch_size);
255            }
256            PassMode::Pair(..) | PassMode::Direct { .. } => {
257                OperandRef::from_immediate_or_packed_pair(bx, val, self.layout).val.store(bx, dst);
258            }
259        }
260    }
261
262    fn store_fn_arg(
263        &self,
264        bx: &mut Builder<'_, 'll, 'tcx>,
265        idx: &mut usize,
266        dst: PlaceRef<'tcx, &'ll Value>,
267    ) {
268        let mut next = || {
269            let val = llvm::get_param(bx.llfn(), *idx as c_uint);
270            *idx += 1;
271            val
272        };
273        match self.mode {
274            PassMode::Ignore => {}
275            PassMode::Pair(..) => {
276                OperandValue::Pair(next(), next()).store(bx, dst);
277            }
278            PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
279                bug!("unsized `ArgAbi` cannot be stored");
280            }
281            PassMode::Direct(_)
282            | PassMode::Indirect { attrs: _, meta_attrs: None, on_stack: _ }
283            | PassMode::Cast { .. } => {
284                let next_arg = next();
285                self.store(bx, next_arg, dst);
286            }
287        }
288    }
289}
290
291impl<'ll, 'tcx> ArgAbiBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
292    fn store_fn_arg(
293        &mut self,
294        arg_abi: &ArgAbi<'tcx, Ty<'tcx>>,
295        idx: &mut usize,
296        dst: PlaceRef<'tcx, Self::Value>,
297    ) {
298        arg_abi.store_fn_arg(self, idx, dst)
299    }
300    fn store_arg(
301        &mut self,
302        arg_abi: &ArgAbi<'tcx, Ty<'tcx>>,
303        val: &'ll Value,
304        dst: PlaceRef<'tcx, &'ll Value>,
305    ) {
306        arg_abi.store(self, val, dst)
307    }
308}
309
310pub(crate) trait FnAbiLlvmExt<'ll, 'tcx> {
311    fn llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type;
312    fn ptr_to_llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type;
313    fn llvm_cconv(&self, cx: &CodegenCx<'ll, 'tcx>) -> llvm::CallConv;
314
315    /// Apply attributes to a function declaration/definition.
316    fn apply_attrs_llfn(
317        &self,
318        cx: &CodegenCx<'ll, 'tcx>,
319        llfn: &'ll Value,
320        instance: Option<ty::Instance<'tcx>>,
321    );
322
323    /// Apply attributes to a function call.
324    fn apply_attrs_callsite(&self, bx: &mut Builder<'_, 'll, 'tcx>, callsite: &'ll Value);
325}
326
327impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
328    fn llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type {
329        // Ignore "extra" args from the call site for C variadic functions.
330        // Only the "fixed" args are part of the LLVM function signature.
331        let args =
332            if self.c_variadic { &self.args[..self.fixed_count as usize] } else { &self.args };
333
334        // This capacity calculation is approximate.
335        let mut llargument_tys = Vec::with_capacity(
336            self.args.len() + if let PassMode::Indirect { .. } = self.ret.mode { 1 } else { 0 },
337        );
338
339        let llreturn_ty = match &self.ret.mode {
340            PassMode::Ignore => cx.type_void(),
341            PassMode::Direct(_) | PassMode::Pair(..) => self.ret.layout.immediate_llvm_type(cx),
342            PassMode::Cast { cast, pad_i32: _ } => cast.llvm_type(cx),
343            PassMode::Indirect { .. } => {
344                llargument_tys.push(cx.type_ptr());
345                cx.type_void()
346            }
347        };
348
349        for arg in args {
350            // Note that the exact number of arguments pushed here is carefully synchronized with
351            // code all over the place, both in the codegen_llvm and codegen_ssa crates. That's how
352            // other code then knows which LLVM argument(s) correspond to the n-th Rust argument.
353            let llarg_ty = match &arg.mode {
354                PassMode::Ignore => continue,
355                PassMode::Direct(_) => {
356                    // ABI-compatible Rust types have the same `layout.abi` (up to validity ranges),
357                    // and for Scalar ABIs the LLVM type is fully determined by `layout.abi`,
358                    // guaranteeing that we generate ABI-compatible LLVM IR.
359                    arg.layout.immediate_llvm_type(cx)
360                }
361                PassMode::Pair(..) => {
362                    // ABI-compatible Rust types have the same `layout.abi` (up to validity ranges),
363                    // so for ScalarPair we can easily be sure that we are generating ABI-compatible
364                    // LLVM IR.
365                    llargument_tys.push(arg.layout.scalar_pair_element_llvm_type(cx, 0, true));
366                    llargument_tys.push(arg.layout.scalar_pair_element_llvm_type(cx, 1, true));
367                    continue;
368                }
369                PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
370                    // Construct the type of a (wide) pointer to `ty`, and pass its two fields.
371                    // Any two ABI-compatible unsized types have the same metadata type and
372                    // moreover the same metadata value leads to the same dynamic size and
373                    // alignment, so this respects ABI compatibility.
374                    let ptr_ty = Ty::new_mut_ptr(cx.tcx, arg.layout.ty);
375                    let ptr_layout = cx.layout_of(ptr_ty);
376                    llargument_tys.push(ptr_layout.scalar_pair_element_llvm_type(cx, 0, true));
377                    llargument_tys.push(ptr_layout.scalar_pair_element_llvm_type(cx, 1, true));
378                    continue;
379                }
380                PassMode::Indirect { attrs: _, meta_attrs: None, on_stack: _ } => cx.type_ptr(),
381                PassMode::Cast { cast, pad_i32 } => {
382                    // add padding
383                    if *pad_i32 {
384                        llargument_tys.push(Reg::i32().llvm_type(cx));
385                    }
386                    // Compute the LLVM type we use for this function from the cast type.
387                    // We assume here that ABI-compatible Rust types have the same cast type.
388                    cast.llvm_type(cx)
389                }
390            };
391            llargument_tys.push(llarg_ty);
392        }
393
394        if self.c_variadic {
395            cx.type_variadic_func(&llargument_tys, llreturn_ty)
396        } else {
397            cx.type_func(&llargument_tys, llreturn_ty)
398        }
399    }
400
401    fn ptr_to_llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type {
402        cx.type_ptr_ext(cx.data_layout().instruction_address_space)
403    }
404
405    fn llvm_cconv(&self, cx: &CodegenCx<'ll, 'tcx>) -> llvm::CallConv {
406        to_llvm_calling_convention(cx.tcx.sess, self.conv)
407    }
408
409    fn apply_attrs_llfn(
410        &self,
411        cx: &CodegenCx<'ll, 'tcx>,
412        llfn: &'ll Value,
413        instance: Option<ty::Instance<'tcx>>,
414    ) {
415        let mut func_attrs = SmallVec::<[_; 3]>::new();
416        if self.ret.layout.is_uninhabited() {
417            func_attrs.push(llvm::AttributeKind::NoReturn.create_attr(cx.llcx));
418        }
419        if !self.can_unwind {
420            func_attrs.push(llvm::AttributeKind::NoUnwind.create_attr(cx.llcx));
421        }
422        match self.conv {
423            CanonAbi::Interrupt(InterruptKind::RiscvMachine) => {
424                func_attrs.push(llvm::CreateAttrStringValue(cx.llcx, "interrupt", "machine"))
425            }
426            CanonAbi::Interrupt(InterruptKind::RiscvSupervisor) => {
427                func_attrs.push(llvm::CreateAttrStringValue(cx.llcx, "interrupt", "supervisor"))
428            }
429            CanonAbi::Arm(ArmCall::CCmseNonSecureEntry) => {
430                func_attrs.push(llvm::CreateAttrString(cx.llcx, "cmse_nonsecure_entry"))
431            }
432            _ => (),
433        }
434        attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &{ func_attrs });
435
436        let mut i = 0;
437        let mut apply = |attrs: &ArgAttributes| {
438            attrs.apply_attrs_to_llfn(llvm::AttributePlace::Argument(i), cx, llfn);
439            i += 1;
440            i - 1
441        };
442
443        let apply_range_attr = |idx: AttributePlace, scalar: rustc_abi::Scalar| {
444            if cx.sess().opts.optimize != config::OptLevel::No
445                && matches!(scalar.primitive(), Primitive::Int(..))
446                // If the value is a boolean, the range is 0..2 and that ultimately
447                // become 0..0 when the type becomes i1, which would be rejected
448                // by the LLVM verifier.
449                && !scalar.is_bool()
450                // LLVM also rejects full range.
451                && !scalar.is_always_valid(cx)
452            {
453                attributes::apply_to_llfn(
454                    llfn,
455                    idx,
456                    &[llvm::CreateRangeAttr(cx.llcx, scalar.size(cx), scalar.valid_range(cx))],
457                );
458            }
459        };
460
461        match &self.ret.mode {
462            PassMode::Direct(attrs) => {
463                attrs.apply_attrs_to_llfn(llvm::AttributePlace::ReturnValue, cx, llfn);
464                if let BackendRepr::Scalar(scalar) = self.ret.layout.backend_repr {
465                    apply_range_attr(llvm::AttributePlace::ReturnValue, scalar);
466                }
467            }
468            PassMode::Indirect { attrs, meta_attrs: _, on_stack } => {
469                assert!(!on_stack);
470                let i = apply(attrs);
471                let sret = llvm::CreateStructRetAttr(
472                    cx.llcx,
473                    cx.type_array(cx.type_i8(), self.ret.layout.size.bytes()),
474                );
475                attributes::apply_to_llfn(llfn, llvm::AttributePlace::Argument(i), &[sret]);
476                if cx.sess().opts.optimize != config::OptLevel::No {
477                    attributes::apply_to_llfn(
478                        llfn,
479                        llvm::AttributePlace::Argument(i),
480                        &[
481                            llvm::AttributeKind::Writable.create_attr(cx.llcx),
482                            llvm::AttributeKind::DeadOnUnwind.create_attr(cx.llcx),
483                        ],
484                    );
485                }
486            }
487            PassMode::Cast { cast, pad_i32: _ } => {
488                cast.attrs.apply_attrs_to_llfn(llvm::AttributePlace::ReturnValue, cx, llfn);
489            }
490            _ => {}
491        }
492        for arg in self.args.iter() {
493            match &arg.mode {
494                PassMode::Ignore => {}
495                PassMode::Indirect { attrs, meta_attrs: None, on_stack: true } => {
496                    let i = apply(attrs);
497                    let byval = llvm::CreateByValAttr(
498                        cx.llcx,
499                        cx.type_array(cx.type_i8(), arg.layout.size.bytes()),
500                    );
501                    attributes::apply_to_llfn(llfn, llvm::AttributePlace::Argument(i), &[byval]);
502                }
503                PassMode::Direct(attrs) => {
504                    let i = apply(attrs);
505                    if let BackendRepr::Scalar(scalar) = arg.layout.backend_repr {
506                        apply_range_attr(llvm::AttributePlace::Argument(i), scalar);
507                    }
508                }
509                PassMode::Indirect { attrs, meta_attrs: None, on_stack: false } => {
510                    let i = apply(attrs);
511                    if cx.sess().opts.optimize != config::OptLevel::No
512                        && llvm_util::get_version() >= (21, 0, 0)
513                    {
514                        attributes::apply_to_llfn(
515                            llfn,
516                            llvm::AttributePlace::Argument(i),
517                            &[llvm::AttributeKind::DeadOnReturn.create_attr(cx.llcx)],
518                        );
519                    }
520                }
521                PassMode::Indirect { attrs, meta_attrs: Some(meta_attrs), on_stack } => {
522                    assert!(!on_stack);
523                    apply(attrs);
524                    apply(meta_attrs);
525                }
526                PassMode::Pair(a, b) => {
527                    let i = apply(a);
528                    let ii = apply(b);
529                    if let BackendRepr::ScalarPair(scalar_a, scalar_b) = arg.layout.backend_repr {
530                        apply_range_attr(llvm::AttributePlace::Argument(i), scalar_a);
531                        let primitive_b = scalar_b.primitive();
532                        let scalar_b = if let rustc_abi::Primitive::Int(int, false) = primitive_b
533                            && let ty::Ref(_, pointee_ty, _) = *arg.layout.ty.kind()
534                            && let ty::Slice(element_ty) = *pointee_ty.kind()
535                            && let elem_size = cx.layout_of(element_ty).size
536                            && elem_size != rustc_abi::Size::ZERO
537                        {
538                            // Ideally the layout calculations would have set the range,
539                            // but that's complicated due to cycles, so in the mean time
540                            // we calculate and apply it here.
541                            debug_assert!(scalar_b.is_always_valid(cx));
542                            let isize_max = int.signed_max() as u64;
543                            rustc_abi::Scalar::Initialized {
544                                value: primitive_b,
545                                valid_range: rustc_abi::WrappingRange {
546                                    start: 0,
547                                    end: u128::from(isize_max / elem_size.bytes()),
548                                },
549                            }
550                        } else {
551                            scalar_b
552                        };
553                        apply_range_attr(llvm::AttributePlace::Argument(ii), scalar_b);
554                    }
555                }
556                PassMode::Cast { cast, pad_i32 } => {
557                    if *pad_i32 {
558                        apply(&ArgAttributes::new());
559                    }
560                    apply(&cast.attrs);
561                }
562            }
563        }
564
565        // If the declaration has an associated instance, compute extra attributes based on that.
566        if let Some(instance) = instance {
567            llfn_attrs_from_instance(
568                cx,
569                cx.tcx,
570                llfn,
571                &cx.tcx.codegen_instance_attrs(instance.def),
572                Some(instance),
573            );
574        }
575    }
576
577    fn apply_attrs_callsite(&self, bx: &mut Builder<'_, 'll, 'tcx>, callsite: &'ll Value) {
578        let mut func_attrs = SmallVec::<[_; 2]>::new();
579        if self.ret.layout.is_uninhabited() {
580            func_attrs.push(llvm::AttributeKind::NoReturn.create_attr(bx.cx.llcx));
581        }
582        if !self.can_unwind {
583            func_attrs.push(llvm::AttributeKind::NoUnwind.create_attr(bx.cx.llcx));
584        }
585        attributes::apply_to_callsite(callsite, llvm::AttributePlace::Function, &{ func_attrs });
586
587        let mut i = 0;
588        let mut apply = |cx: &CodegenCx<'_, '_>, attrs: &ArgAttributes| {
589            attrs.apply_attrs_to_callsite(llvm::AttributePlace::Argument(i), cx, callsite);
590            i += 1;
591            i - 1
592        };
593        match &self.ret.mode {
594            PassMode::Direct(attrs) => {
595                attrs.apply_attrs_to_callsite(llvm::AttributePlace::ReturnValue, bx.cx, callsite);
596            }
597            PassMode::Indirect { attrs, meta_attrs: _, on_stack } => {
598                assert!(!on_stack);
599                let i = apply(bx.cx, attrs);
600                let sret = llvm::CreateStructRetAttr(
601                    bx.cx.llcx,
602                    bx.cx.type_array(bx.cx.type_i8(), self.ret.layout.size.bytes()),
603                );
604                attributes::apply_to_callsite(callsite, llvm::AttributePlace::Argument(i), &[sret]);
605            }
606            PassMode::Cast { cast, pad_i32: _ } => {
607                cast.attrs.apply_attrs_to_callsite(
608                    llvm::AttributePlace::ReturnValue,
609                    bx.cx,
610                    callsite,
611                );
612            }
613            _ => {}
614        }
615        for arg in self.args.iter() {
616            match &arg.mode {
617                PassMode::Ignore => {}
618                PassMode::Indirect { attrs, meta_attrs: None, on_stack: true } => {
619                    let i = apply(bx.cx, attrs);
620                    let byval = llvm::CreateByValAttr(
621                        bx.cx.llcx,
622                        bx.cx.type_array(bx.cx.type_i8(), arg.layout.size.bytes()),
623                    );
624                    attributes::apply_to_callsite(
625                        callsite,
626                        llvm::AttributePlace::Argument(i),
627                        &[byval],
628                    );
629                }
630                PassMode::Direct(attrs)
631                | PassMode::Indirect { attrs, meta_attrs: None, on_stack: false } => {
632                    apply(bx.cx, attrs);
633                }
634                PassMode::Indirect { attrs, meta_attrs: Some(meta_attrs), on_stack: _ } => {
635                    apply(bx.cx, attrs);
636                    apply(bx.cx, meta_attrs);
637                }
638                PassMode::Pair(a, b) => {
639                    apply(bx.cx, a);
640                    apply(bx.cx, b);
641                }
642                PassMode::Cast { cast, pad_i32 } => {
643                    if *pad_i32 {
644                        apply(bx.cx, &ArgAttributes::new());
645                    }
646                    apply(bx.cx, &cast.attrs);
647                }
648            }
649        }
650
651        let cconv = self.llvm_cconv(&bx.cx);
652        if cconv != llvm::CCallConv {
653            llvm::SetInstructionCallConv(callsite, cconv);
654        }
655
656        if self.conv == CanonAbi::Arm(ArmCall::CCmseNonSecureCall) {
657            // This will probably get ignored on all targets but those supporting the TrustZone-M
658            // extension (thumbv8m targets).
659            let cmse_nonsecure_call = llvm::CreateAttrString(bx.cx.llcx, "cmse_nonsecure_call");
660            attributes::apply_to_callsite(
661                callsite,
662                llvm::AttributePlace::Function,
663                &[cmse_nonsecure_call],
664            );
665        }
666
667        // Some intrinsics require that an elementtype attribute (with the pointee type of a
668        // pointer argument) is added to the callsite.
669        let element_type_index = unsafe { llvm::LLVMRustGetElementTypeArgIndex(callsite) };
670        if element_type_index >= 0 {
671            let arg_ty = self.args[element_type_index as usize].layout.ty;
672            let pointee_ty = arg_ty.builtin_deref(true).expect("Must be pointer argument");
673            let element_type_attr = unsafe {
674                llvm::LLVMRustCreateElementTypeAttr(bx.llcx, bx.layout_of(pointee_ty).llvm_type(bx))
675            };
676            attributes::apply_to_callsite(
677                callsite,
678                llvm::AttributePlace::Argument(element_type_index as u32),
679                &[element_type_attr],
680            );
681        }
682    }
683}
684
685impl AbiBuilderMethods for Builder<'_, '_, '_> {
686    fn get_param(&mut self, index: usize) -> Self::Value {
687        llvm::get_param(self.llfn(), index as c_uint)
688    }
689}
690
691/// Determines the appropriate [`llvm::CallConv`] to use for a given function
692/// ABI, for the current target.
693pub(crate) fn to_llvm_calling_convention(sess: &Session, abi: CanonAbi) -> llvm::CallConv {
694    match abi {
695        CanonAbi::C | CanonAbi::Rust => llvm::CCallConv,
696        CanonAbi::RustCold => llvm::PreserveMost,
697        // Functions with this calling convention can only be called from assembly, but it is
698        // possible to declare an `extern "custom"` block, so the backend still needs a calling
699        // convention for declaring foreign functions.
700        CanonAbi::Custom => llvm::CCallConv,
701        CanonAbi::GpuKernel => match &sess.target.arch {
702            Arch::AmdGpu => llvm::AmdgpuKernel,
703            Arch::Nvptx64 => llvm::PtxKernel,
704            arch => panic!("Architecture {arch} does not support GpuKernel calling convention"),
705        },
706        CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
707            InterruptKind::Avr => llvm::AvrInterrupt,
708            InterruptKind::AvrNonBlocking => llvm::AvrNonBlockingInterrupt,
709            InterruptKind::Msp430 => llvm::Msp430Intr,
710            InterruptKind::RiscvMachine | InterruptKind::RiscvSupervisor => llvm::CCallConv,
711            InterruptKind::X86 => llvm::X86_Intr,
712        },
713        CanonAbi::Arm(arm_call) => match arm_call {
714            ArmCall::Aapcs => llvm::ArmAapcsCallConv,
715            ArmCall::CCmseNonSecureCall | ArmCall::CCmseNonSecureEntry => llvm::CCallConv,
716        },
717        CanonAbi::X86(x86_call) => match x86_call {
718            X86Call::Fastcall => llvm::X86FastcallCallConv,
719            X86Call::Stdcall => llvm::X86StdcallCallConv,
720            X86Call::SysV64 => llvm::X86_64_SysV,
721            X86Call::Thiscall => llvm::X86_ThisCall,
722            X86Call::Vectorcall => llvm::X86_VectorCall,
723            X86Call::Win64 => llvm::X86_64_Win64,
724        },
725    }
726}
rustc_codegen_llvm/abi.rs

rustc_codegen_llvm/
abi.rs
