bjoernager/rust
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Auto merge of #86873 - nikic:opaque-ptrs, r=nagisa

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Improve opaque pointers support

Opaque pointers are coming, and rustc is not ready.

This adds partial support by passing an explicit load type to LLVM. Two issues I've encountered:
 * The necessary type was not available at the point where non-temporal copies were generated. I've pushed the code for that upwards out of the memcpy implementation and moved the position of a cast to make do with the types we have available. (I'm not sure that cast is needed at all, but have retained it in the interest of conservativeness.)
 * The `PlaceRef::project_deref()` function used during debuginfo generation seems to be buggy in some way -- though I haven't figured out specifically what it does wrong. Replacing it with `load_operand().deref()` did the trick, but I don't really know what I'm doing here.
This commit is contained in:
bors 2021-07-10 19:01:41 +00:00
commit 432e145bd5
13 changed files with 81 additions and 74 deletions
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10
compiler/rustc_codegen_ssa/src/meth.rs
View file

@ -20,10 +20,11 @@ impl<'a, 'tcx> VirtualIndex {
// Load the data pointer from the object.
debug!("get_fn({:?}, {:?})", llvtable, self);
let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(bx.fn_ptr_backend_type(fn_abi)));
let llty = bx.fn_ptr_backend_type(fn_abi);
let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(llty));
let ptr_align = bx.tcx().data_layout.pointer_align.abi;
let gep = bx.inbounds_gep(llvtable, &[bx.const_usize(self.0)]);
let ptr = bx.load(gep, ptr_align);
let ptr = bx.load(llty, gep, ptr_align);
bx.nonnull_metadata(ptr);
// Vtable loads are invariant.
bx.set_invariant_load(ptr);
@ -38,10 +39,11 @@ impl<'a, 'tcx> VirtualIndex {
// Load the data pointer from the object.
debug!("get_int({:?}, {:?})", llvtable, self);
let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(bx.type_isize()));
let llty = bx.type_isize();
let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(llty));
let usize_align = bx.tcx().data_layout.pointer_align.abi;
let gep = bx.inbounds_gep(llvtable, &[bx.const_usize(self.0)]);
let ptr = bx.load(gep, usize_align);
let ptr = bx.load(llty, gep, usize_align);
// Vtable loads are invariant.
bx.set_invariant_load(ptr);
ptr

14
compiler/rustc_codegen_ssa/src/mir/block.rs
View file

@ -260,7 +260,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
PassMode::Direct(_) | PassMode::Pair(..) => {
let op = self.codegen_consume(&mut bx, mir::Place::return_place().as_ref());
if let Ref(llval, _, align) = op.val {
bx.load(llval, align)
bx.load(bx.backend_type(op.layout), llval, align)
} else {
op.immediate_or_packed_pair(&mut bx)
}
@ -287,8 +287,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
llval
}
};
let addr = bx.pointercast(llslot, bx.type_ptr_to(bx.cast_backend_type(&cast_ty)));
bx.load(addr, self.fn_abi.ret.layout.align.abi)
let ty = bx.cast_backend_type(&cast_ty);
let addr = bx.pointercast(llslot, bx.type_ptr_to(ty));
bx.load(ty, addr, self.fn_abi.ret.layout.align.abi)
}
};
bx.ret(llval);
@ -1086,15 +1087,16 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
if by_ref && !arg.is_indirect() {
// Have to load the argument, maybe while casting it.
if let PassMode::Cast(ty) = arg.mode {
let addr = bx.pointercast(llval, bx.type_ptr_to(bx.cast_backend_type(&ty)));
llval = bx.load(addr, align.min(arg.layout.align.abi));
let llty = bx.cast_backend_type(&ty);
let addr = bx.pointercast(llval, bx.type_ptr_to(llty));
llval = bx.load(llty, addr, align.min(arg.layout.align.abi));
} else {
// We can't use `PlaceRef::load` here because the argument
// may have a type we don't treat as immediate, but the ABI
// used for this call is passing it by-value. In that case,
// the load would just produce `OperandValue::Ref` instead
// of the `OperandValue::Immediate` we need for the call.
llval = bx.load(llval, align);
llval = bx.load(bx.backend_type(arg.layout), llval, align);
if let abi::Abi::Scalar(ref scalar) = arg.layout.abi {
if scalar.is_bool() {
bx.range_metadata(llval, 0..2);

2
compiler/rustc_codegen_ssa/src/mir/debuginfo.rs
View file

@ -274,7 +274,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
match *elem {
mir::ProjectionElem::Deref => {
indirect_offsets.push(Size::ZERO);
place = place.project_deref(bx);
place = bx.load_operand(place).deref(bx.cx());
}
mir::ProjectionElem::Field(field, _) => {
let i = field.index();

9
compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
View file

@ -448,15 +448,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
if ty.is_unsafe_ptr() {
// Some platforms do not support atomic operations on pointers,
// so we cast to integer first...
let ptr_llty = bx.type_ptr_to(bx.type_isize());
let llty = bx.type_isize();
let ptr_llty = bx.type_ptr_to(llty);
source = bx.pointercast(source, ptr_llty);
}
let result = bx.atomic_load(source, order, size);
if ty.is_unsafe_ptr() {
let result = bx.atomic_load(llty, source, order, size);
// ... and then cast the result back to a pointer
bx.inttoptr(result, bx.backend_type(layout))
} else {
result
bx.atomic_load(bx.backend_type(layout), source, order, size)
}
} else {
return invalid_monomorphization(ty);

8
compiler/rustc_codegen_ssa/src/mir/operand.rs
View file

@ -289,6 +289,14 @@ impl<'a, 'tcx, V: CodegenObject> OperandValue<V> {
}
match self {
OperandValue::Ref(r, None, source_align) => {
if flags.contains(MemFlags::NONTEMPORAL) {
// HACK(nox): This is inefficient but there is no nontemporal memcpy.
let ty = bx.backend_type(dest.layout);
let ptr = bx.pointercast(r, bx.type_ptr_to(ty));
let val = bx.load(ty, ptr, source_align);
bx.store_with_flags(val, dest.llval, dest.align, flags);
return;
}
base::memcpy_ty(bx, dest.llval, dest.align, r, source_align, dest.layout, flags)
}
OperandValue::Ref(_, Some(_), _) => {

12
compiler/rustc_codegen_ssa/src/mir/place.rs
View file

@ -402,18 +402,6 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
downcast
}
pub fn project_deref<Bx: BuilderMethods<'a, 'tcx, Value = V>>(&self, bx: &mut Bx) -> Self {
let target_ty = self.layout.ty.builtin_deref(true).expect("failed to deref");
let layout = bx.layout_of(target_ty.ty);
PlaceRef {
llval: bx.load(self.llval, self.align),
llextra: None,
layout,
align: layout.align.abi,
}
}
pub fn storage_live<Bx: BuilderMethods<'a, 'tcx, Value = V>>(&self, bx: &mut Bx) {
bx.lifetime_start(self.llval, self.layout.size);
}

12
compiler/rustc_codegen_ssa/src/traits/builder.rs
View file

@ -137,9 +137,15 @@ pub trait BuilderMethods<'a, 'tcx>:
fn dynamic_alloca(&mut self, ty: Self::Type, align: Align) -> Self::Value;
fn array_alloca(&mut self, ty: Self::Type, len: Self::Value, align: Align) -> Self::Value;
fn load(&mut self, ptr: Self::Value, align: Align) -> Self::Value;
fn volatile_load(&mut self, ptr: Self::Value) -> Self::Value;
fn atomic_load(&mut self, ptr: Self::Value, order: AtomicOrdering, size: Size) -> Self::Value;
fn load(&mut self, ty: Self::Type, ptr: Self::Value, align: Align) -> Self::Value;
fn volatile_load(&mut self, ty: Self::Type, ptr: Self::Value) -> Self::Value;
fn atomic_load(
&mut self,
ty: Self::Type,
ptr: Self::Value,
order: AtomicOrdering,
size: Size,
) -> Self::Value;
fn load_operand(&mut self, place: PlaceRef<'tcx, Self::Value>)
-> OperandRef<'tcx, Self::Value>;