rust/compiler/rustc_codegen_llvm/src/abi.rs
Scott McMurray e90be842fb Add support for emitting functions with coldcc in LLVM
The eventual goal is to try using this for things like the internal panicking stuff, to see whether it helps.
2022-05-30 00:19:23 -07:00

584 lines
22 KiB
Rust

use crate::attributes;
use crate::builder::Builder;
use crate::context::CodegenCx;
use crate::llvm::{self, Attribute, AttributePlace};
use crate::type_::Type;
use crate::type_of::LayoutLlvmExt;
use crate::value::Value;
use rustc_codegen_ssa::mir::operand::OperandValue;
use rustc_codegen_ssa::mir::place::PlaceRef;
use rustc_codegen_ssa::traits::*;
use rustc_codegen_ssa::MemFlags;
use rustc_middle::bug;
use rustc_middle::ty::layout::LayoutOf;
pub use rustc_middle::ty::layout::{FAT_PTR_ADDR, FAT_PTR_EXTRA};
use rustc_middle::ty::Ty;
use rustc_session::config;
use rustc_target::abi::call::ArgAbi;
pub use rustc_target::abi::call::*;
use rustc_target::abi::{self, HasDataLayout, Int};
pub use rustc_target::spec::abi::Abi;
use libc::c_uint;
use smallvec::SmallVec;
pub trait ArgAttributesExt {
fn apply_attrs_to_llfn(&self, idx: AttributePlace, cx: &CodegenCx<'_, '_>, llfn: &Value);
fn apply_attrs_to_callsite(
&self,
idx: AttributePlace,
cx: &CodegenCx<'_, '_>,
callsite: &Value,
);
}
fn should_use_mutable_noalias(cx: &CodegenCx<'_, '_>) -> bool {
// LLVM prior to version 12 had known miscompiles in the presence of
// noalias attributes (see #54878), but we don't support earlier
// versions at all anymore. We now enable mutable noalias by default.
cx.tcx.sess.opts.debugging_opts.mutable_noalias.unwrap_or(true)
}
const ABI_AFFECTING_ATTRIBUTES: [(ArgAttribute, llvm::AttributeKind); 1] =
[(ArgAttribute::InReg, llvm::AttributeKind::InReg)];
const OPTIMIZATION_ATTRIBUTES: [(ArgAttribute, llvm::AttributeKind); 5] = [
(ArgAttribute::NoAlias, llvm::AttributeKind::NoAlias),
(ArgAttribute::NoCapture, llvm::AttributeKind::NoCapture),
(ArgAttribute::NonNull, llvm::AttributeKind::NonNull),
(ArgAttribute::ReadOnly, llvm::AttributeKind::ReadOnly),
(ArgAttribute::NoUndef, llvm::AttributeKind::NoUndef),
];
fn get_attrs<'ll>(this: &ArgAttributes, cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'ll Attribute; 8]> {
let mut regular = this.regular;
let mut attrs = SmallVec::new();
// ABI-affecting attributes must always be applied
for (attr, llattr) in ABI_AFFECTING_ATTRIBUTES {
if regular.contains(attr) {
attrs.push(llattr.create_attr(cx.llcx));
}
}
if let Some(align) = this.pointee_align {
attrs.push(llvm::CreateAlignmentAttr(cx.llcx, align.bytes()));
}
match this.arg_ext {
ArgExtension::None => {}
ArgExtension::Zext => attrs.push(llvm::AttributeKind::ZExt.create_attr(cx.llcx)),
ArgExtension::Sext => attrs.push(llvm::AttributeKind::SExt.create_attr(cx.llcx)),
}
// Only apply remaining attributes when optimizing
if cx.sess().opts.optimize != config::OptLevel::No {
let deref = this.pointee_size.bytes();
if deref != 0 {
if regular.contains(ArgAttribute::NonNull) {
attrs.push(llvm::CreateDereferenceableAttr(cx.llcx, deref));
} else {
attrs.push(llvm::CreateDereferenceableOrNullAttr(cx.llcx, deref));
}
regular -= ArgAttribute::NonNull;
}
for (attr, llattr) in OPTIMIZATION_ATTRIBUTES {
if regular.contains(attr) {
attrs.push(llattr.create_attr(cx.llcx));
}
}
if regular.contains(ArgAttribute::NoAliasMutRef) && should_use_mutable_noalias(cx) {
attrs.push(llvm::AttributeKind::NoAlias.create_attr(cx.llcx));
}
}
attrs
}
impl ArgAttributesExt for ArgAttributes {
fn apply_attrs_to_llfn(&self, idx: AttributePlace, cx: &CodegenCx<'_, '_>, llfn: &Value) {
let attrs = get_attrs(self, cx);
attributes::apply_to_llfn(llfn, idx, &attrs);
}
fn apply_attrs_to_callsite(
&self,
idx: AttributePlace,
cx: &CodegenCx<'_, '_>,
callsite: &Value,
) {
let attrs = get_attrs(self, cx);
attributes::apply_to_callsite(callsite, idx, &attrs);
}
}
pub trait LlvmType {
fn llvm_type<'ll>(&self, cx: &CodegenCx<'ll, '_>) -> &'ll Type;
}
impl LlvmType for Reg {
fn llvm_type<'ll>(&self, cx: &CodegenCx<'ll, '_>) -> &'ll Type {
match self.kind {
RegKind::Integer => cx.type_ix(self.size.bits()),
RegKind::Float => match self.size.bits() {
32 => cx.type_f32(),
64 => cx.type_f64(),
_ => bug!("unsupported float: {:?}", self),
},
RegKind::Vector => cx.type_vector(cx.type_i8(), self.size.bytes()),
}
}
}
impl LlvmType for CastTarget {
fn llvm_type<'ll>(&self, cx: &CodegenCx<'ll, '_>) -> &'ll Type {
let rest_ll_unit = self.rest.unit.llvm_type(cx);
let (rest_count, rem_bytes) = if self.rest.unit.size.bytes() == 0 {
(0, 0)
} else {
(
self.rest.total.bytes() / self.rest.unit.size.bytes(),
self.rest.total.bytes() % self.rest.unit.size.bytes(),
)
};
if self.prefix.iter().all(|x| x.is_none()) {
// Simplify to a single unit when there is no prefix and size <= unit size
if self.rest.total <= self.rest.unit.size {
return rest_ll_unit;
}
// Simplify to array when all chunks are the same size and type
if rem_bytes == 0 {
return cx.type_array(rest_ll_unit, rest_count);
}
}
// Create list of fields in the main structure
let mut args: Vec<_> = self
.prefix
.iter()
.flat_map(|option_reg| option_reg.map(|reg| reg.llvm_type(cx)))
.chain((0..rest_count).map(|_| rest_ll_unit))
.collect();
// Append final integer
if rem_bytes != 0 {
// Only integers can be really split further.
assert_eq!(self.rest.unit.kind, RegKind::Integer);
args.push(cx.type_ix(rem_bytes * 8));
}
cx.type_struct(&args, false)
}
}
pub trait ArgAbiExt<'ll, 'tcx> {
fn memory_ty(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type;
fn store(
&self,
bx: &mut Builder<'_, 'll, 'tcx>,
val: &'ll Value,
dst: PlaceRef<'tcx, &'ll Value>,
);
fn store_fn_arg(
&self,
bx: &mut Builder<'_, 'll, 'tcx>,
idx: &mut usize,
dst: PlaceRef<'tcx, &'ll Value>,
);
}
impl<'ll, 'tcx> ArgAbiExt<'ll, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
/// Gets the LLVM type for a place of the original Rust type of
/// this argument/return, i.e., the result of `type_of::type_of`.
fn memory_ty(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type {
self.layout.llvm_type(cx)
}
/// Stores a direct/indirect value described by this ArgAbi into a
/// place for the original Rust type of this argument/return.
/// Can be used for both storing formal arguments into Rust variables
/// or results of call/invoke instructions into their destinations.
fn store(
&self,
bx: &mut Builder<'_, 'll, 'tcx>,
val: &'ll Value,
dst: PlaceRef<'tcx, &'ll Value>,
) {
if self.is_ignore() {
return;
}
if self.is_sized_indirect() {
OperandValue::Ref(val, None, self.layout.align.abi).store(bx, dst)
} else if self.is_unsized_indirect() {
bug!("unsized `ArgAbi` must be handled through `store_fn_arg`");
} else if let PassMode::Cast(cast) = self.mode {
// FIXME(eddyb): Figure out when the simpler Store is safe, clang
// uses it for i16 -> {i8, i8}, but not for i24 -> {i8, i8, i8}.
let can_store_through_cast_ptr = false;
if can_store_through_cast_ptr {
let cast_ptr_llty = bx.type_ptr_to(cast.llvm_type(bx));
let cast_dst = bx.pointercast(dst.llval, cast_ptr_llty);
bx.store(val, cast_dst, self.layout.align.abi);
} else {
// The actual return type is a struct, but the ABI
// adaptation code has cast it into some scalar type. The
// code that follows is the only reliable way I have
// found to do a transform like i64 -> {i32,i32}.
// Basically we dump the data onto the stack then memcpy it.
//
// Other approaches I tried:
// - Casting rust ret pointer to the foreign type and using Store
// is (a) unsafe if size of foreign type > size of rust type and
// (b) runs afoul of strict aliasing rules, yielding invalid
// assembly under -O (specifically, the store gets removed).
// - Truncating foreign type to correct integral type and then
// bitcasting to the struct type yields invalid cast errors.
// We instead thus allocate some scratch space...
let scratch_size = cast.size(bx);
let scratch_align = cast.align(bx);
let llscratch = bx.alloca(cast.llvm_type(bx), scratch_align);
bx.lifetime_start(llscratch, scratch_size);
// ... where we first store the value...
bx.store(val, llscratch, scratch_align);
// ... and then memcpy it to the intended destination.
bx.memcpy(
dst.llval,
self.layout.align.abi,
llscratch,
scratch_align,
bx.const_usize(self.layout.size.bytes()),
MemFlags::empty(),
);
bx.lifetime_end(llscratch, scratch_size);
}
} else {
OperandValue::Immediate(val).store(bx, dst);
}
}
fn store_fn_arg(
&self,
bx: &mut Builder<'_, 'll, 'tcx>,
idx: &mut usize,
dst: PlaceRef<'tcx, &'ll Value>,
) {
let mut next = || {
let val = llvm::get_param(bx.llfn(), *idx as c_uint);
*idx += 1;
val
};
match self.mode {
PassMode::Ignore => {}
PassMode::Pair(..) => {
OperandValue::Pair(next(), next()).store(bx, dst);
}
PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => {
OperandValue::Ref(next(), Some(next()), self.layout.align.abi).store(bx, dst);
}
PassMode::Direct(_)
| PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ }
| PassMode::Cast(_) => {
let next_arg = next();
self.store(bx, next_arg, dst);
}
}
}
}
impl<'ll, 'tcx> ArgAbiMethods<'tcx> for Builder<'_, 'll, 'tcx> {
fn store_fn_arg(
&mut self,
arg_abi: &ArgAbi<'tcx, Ty<'tcx>>,
idx: &mut usize,
dst: PlaceRef<'tcx, Self::Value>,
) {
arg_abi.store_fn_arg(self, idx, dst)
}
fn store_arg(
&mut self,
arg_abi: &ArgAbi<'tcx, Ty<'tcx>>,
val: &'ll Value,
dst: PlaceRef<'tcx, &'ll Value>,
) {
arg_abi.store(self, val, dst)
}
fn arg_memory_ty(&self, arg_abi: &ArgAbi<'tcx, Ty<'tcx>>) -> &'ll Type {
arg_abi.memory_ty(self)
}
}
pub trait FnAbiLlvmExt<'ll, 'tcx> {
fn llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type;
fn ptr_to_llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type;
fn llvm_cconv(&self) -> llvm::CallConv;
fn apply_attrs_llfn(&self, cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value);
fn apply_attrs_callsite(&self, bx: &mut Builder<'_, 'll, 'tcx>, callsite: &'ll Value);
}
impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
fn llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type {
// Ignore "extra" args from the call site for C variadic functions.
// Only the "fixed" args are part of the LLVM function signature.
let args = if self.c_variadic { &self.args[..self.fixed_count] } else { &self.args };
let args_capacity: usize = args.iter().map(|arg|
if arg.pad.is_some() { 1 } else { 0 } +
if let PassMode::Pair(_, _) = arg.mode { 2 } else { 1 }
).sum();
let mut llargument_tys = Vec::with_capacity(
if let PassMode::Indirect { .. } = self.ret.mode { 1 } else { 0 } + args_capacity,
);
let llreturn_ty = match self.ret.mode {
PassMode::Ignore => cx.type_void(),
PassMode::Direct(_) | PassMode::Pair(..) => self.ret.layout.immediate_llvm_type(cx),
PassMode::Cast(cast) => cast.llvm_type(cx),
PassMode::Indirect { .. } => {
llargument_tys.push(cx.type_ptr_to(self.ret.memory_ty(cx)));
cx.type_void()
}
};
for arg in args {
// add padding
if let Some(ty) = arg.pad {
llargument_tys.push(ty.llvm_type(cx));
}
let llarg_ty = match arg.mode {
PassMode::Ignore => continue,
PassMode::Direct(_) => arg.layout.immediate_llvm_type(cx),
PassMode::Pair(..) => {
llargument_tys.push(arg.layout.scalar_pair_element_llvm_type(cx, 0, true));
llargument_tys.push(arg.layout.scalar_pair_element_llvm_type(cx, 1, true));
continue;
}
PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => {
let ptr_ty = cx.tcx.mk_mut_ptr(arg.layout.ty);
let ptr_layout = cx.layout_of(ptr_ty);
llargument_tys.push(ptr_layout.scalar_pair_element_llvm_type(cx, 0, true));
llargument_tys.push(ptr_layout.scalar_pair_element_llvm_type(cx, 1, true));
continue;
}
PassMode::Cast(cast) => cast.llvm_type(cx),
PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => {
cx.type_ptr_to(arg.memory_ty(cx))
}
};
llargument_tys.push(llarg_ty);
}
if self.c_variadic {
cx.type_variadic_func(&llargument_tys, llreturn_ty)
} else {
cx.type_func(&llargument_tys, llreturn_ty)
}
}
fn ptr_to_llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type {
unsafe {
llvm::LLVMPointerType(
self.llvm_type(cx),
cx.data_layout().instruction_address_space.0 as c_uint,
)
}
}
fn llvm_cconv(&self) -> llvm::CallConv {
match self.conv {
Conv::C | Conv::Rust | Conv::CCmseNonSecureCall => llvm::CCallConv,
Conv::RustCold => llvm::ColdCallConv,
Conv::AmdGpuKernel => llvm::AmdGpuKernel,
Conv::AvrInterrupt => llvm::AvrInterrupt,
Conv::AvrNonBlockingInterrupt => llvm::AvrNonBlockingInterrupt,
Conv::ArmAapcs => llvm::ArmAapcsCallConv,
Conv::Msp430Intr => llvm::Msp430Intr,
Conv::PtxKernel => llvm::PtxKernel,
Conv::X86Fastcall => llvm::X86FastcallCallConv,
Conv::X86Intr => llvm::X86_Intr,
Conv::X86Stdcall => llvm::X86StdcallCallConv,
Conv::X86ThisCall => llvm::X86_ThisCall,
Conv::X86VectorCall => llvm::X86_VectorCall,
Conv::X86_64SysV => llvm::X86_64_SysV,
Conv::X86_64Win64 => llvm::X86_64_Win64,
}
}
fn apply_attrs_llfn(&self, cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value) {
let mut func_attrs = SmallVec::<[_; 2]>::new();
if self.ret.layout.abi.is_uninhabited() {
func_attrs.push(llvm::AttributeKind::NoReturn.create_attr(cx.llcx));
}
if !self.can_unwind {
func_attrs.push(llvm::AttributeKind::NoUnwind.create_attr(cx.llcx));
}
attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &{ func_attrs });
let mut i = 0;
let mut apply = |attrs: &ArgAttributes| {
attrs.apply_attrs_to_llfn(llvm::AttributePlace::Argument(i), cx, llfn);
i += 1;
i - 1
};
match self.ret.mode {
PassMode::Direct(ref attrs) => {
attrs.apply_attrs_to_llfn(llvm::AttributePlace::ReturnValue, cx, llfn);
}
PassMode::Indirect { ref attrs, extra_attrs: _, on_stack } => {
assert!(!on_stack);
let i = apply(attrs);
let sret = llvm::CreateStructRetAttr(cx.llcx, self.ret.layout.llvm_type(cx));
attributes::apply_to_llfn(llfn, llvm::AttributePlace::Argument(i), &[sret]);
}
PassMode::Cast(cast) => {
cast.attrs.apply_attrs_to_llfn(llvm::AttributePlace::ReturnValue, cx, llfn);
}
_ => {}
}
for arg in &self.args {
if arg.pad.is_some() {
apply(&ArgAttributes::new());
}
match arg.mode {
PassMode::Ignore => {}
PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: true } => {
let i = apply(attrs);
let byval = llvm::CreateByValAttr(cx.llcx, arg.layout.llvm_type(cx));
attributes::apply_to_llfn(llfn, llvm::AttributePlace::Argument(i), &[byval]);
}
PassMode::Direct(ref attrs)
| PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: false } => {
apply(attrs);
}
PassMode::Indirect { ref attrs, extra_attrs: Some(ref extra_attrs), on_stack } => {
assert!(!on_stack);
apply(attrs);
apply(extra_attrs);
}
PassMode::Pair(ref a, ref b) => {
apply(a);
apply(b);
}
PassMode::Cast(cast) => {
apply(&cast.attrs);
}
}
}
}
fn apply_attrs_callsite(&self, bx: &mut Builder<'_, 'll, 'tcx>, callsite: &'ll Value) {
let mut func_attrs = SmallVec::<[_; 2]>::new();
if self.ret.layout.abi.is_uninhabited() {
func_attrs.push(llvm::AttributeKind::NoReturn.create_attr(bx.cx.llcx));
}
if !self.can_unwind {
func_attrs.push(llvm::AttributeKind::NoUnwind.create_attr(bx.cx.llcx));
}
attributes::apply_to_callsite(callsite, llvm::AttributePlace::Function, &{ func_attrs });
let mut i = 0;
let mut apply = |cx: &CodegenCx<'_, '_>, attrs: &ArgAttributes| {
attrs.apply_attrs_to_callsite(llvm::AttributePlace::Argument(i), cx, callsite);
i += 1;
i - 1
};
match self.ret.mode {
PassMode::Direct(ref attrs) => {
attrs.apply_attrs_to_callsite(llvm::AttributePlace::ReturnValue, bx.cx, callsite);
}
PassMode::Indirect { ref attrs, extra_attrs: _, on_stack } => {
assert!(!on_stack);
let i = apply(bx.cx, attrs);
let sret = llvm::CreateStructRetAttr(bx.cx.llcx, self.ret.layout.llvm_type(bx));
attributes::apply_to_callsite(callsite, llvm::AttributePlace::Argument(i), &[sret]);
}
PassMode::Cast(cast) => {
cast.attrs.apply_attrs_to_callsite(
llvm::AttributePlace::ReturnValue,
&bx.cx,
callsite,
);
}
_ => {}
}
if let abi::Abi::Scalar(scalar) = self.ret.layout.abi {
// If the value is a boolean, the range is 0..2 and that ultimately
// become 0..0 when the type becomes i1, which would be rejected
// by the LLVM verifier.
if let Int(..) = scalar.primitive() {
if !scalar.is_bool() && !scalar.is_always_valid(bx) {
bx.range_metadata(callsite, scalar.valid_range(bx));
}
}
}
for arg in &self.args {
if arg.pad.is_some() {
apply(bx.cx, &ArgAttributes::new());
}
match arg.mode {
PassMode::Ignore => {}
PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: true } => {
let i = apply(bx.cx, attrs);
let byval = llvm::CreateByValAttr(bx.cx.llcx, arg.layout.llvm_type(bx));
attributes::apply_to_callsite(
callsite,
llvm::AttributePlace::Argument(i),
&[byval],
);
}
PassMode::Direct(ref attrs)
| PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: false } => {
apply(bx.cx, attrs);
}
PassMode::Indirect {
ref attrs,
extra_attrs: Some(ref extra_attrs),
on_stack: _,
} => {
apply(bx.cx, attrs);
apply(bx.cx, extra_attrs);
}
PassMode::Pair(ref a, ref b) => {
apply(bx.cx, a);
apply(bx.cx, b);
}
PassMode::Cast(cast) => {
apply(bx.cx, &cast.attrs);
}
}
}
let cconv = self.llvm_cconv();
if cconv != llvm::CCallConv {
llvm::SetInstructionCallConv(callsite, cconv);
}
if self.conv == Conv::CCmseNonSecureCall {
// This will probably get ignored on all targets but those supporting the TrustZone-M
// extension (thumbv8m targets).
let cmse_nonsecure_call = llvm::CreateAttrString(bx.cx.llcx, "cmse_nonsecure_call");
attributes::apply_to_callsite(
callsite,
llvm::AttributePlace::Function,
&[cmse_nonsecure_call],
);
}
}
}
impl<'tcx> AbiBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
fn apply_attrs_callsite(&mut self, fn_abi: &FnAbi<'tcx, Ty<'tcx>>, callsite: Self::Value) {
fn_abi.apply_attrs_callsite(self, callsite)
}
fn get_param(&mut self, index: usize) -> Self::Value {
llvm::get_param(self.llfn(), index as c_uint)
}
}