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rustc: use an offset instead of a field path in Layout::StructWrappedNullablePointer.

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This commit is contained in:
Eduard-Mihai Burtescu 2017-09-10 23:53:57 +03:00
parent 50a3fd0097
commit bc8e1f7efa
6 changed files with 139 additions and 115 deletions
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157
src/librustc/ty/layout.rs
View File

@ -841,35 +841,47 @@ impl<'a, 'tcx> Struct {
})
}
/// Find the path leading to a non-zero leaf field, starting from
/// Find the offset of a non-zero leaf field, starting from
/// the given type and recursing through aggregates.
/// The tuple is `(path, source_path)`,
/// where `path` is in memory order and `source_path` in source order.
/// The tuple is `(offset, primitive, source_path)`.
// FIXME(eddyb) track value ranges and traverse already optimized enums.
fn non_zero_field_in_type(tcx: TyCtxt<'a, 'tcx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
ty: Ty<'tcx>)
-> Result<Option<(FieldPath, FieldPath)>, LayoutError<'tcx>> {
match (ty.layout(tcx, param_env)?, &ty.sty) {
(&Scalar { non_zero: true, .. }, _) |
(&CEnum { non_zero: true, .. }, _) => Ok(Some((vec![], vec![]))),
-> Result<Option<(Size, Primitive, FieldPath)>, LayoutError<'tcx>> {
let layout = ty.layout(tcx, param_env)?;
match (layout, &ty.sty) {
(&Scalar { non_zero: true, value, .. }, _) => {
Ok(Some((Size::from_bytes(0), value, vec![])))
}
(&CEnum { non_zero: true, discr, .. }, _) => {
Ok(Some((Size::from_bytes(0), Int(discr), vec![])))
}
(&FatPointer { non_zero: true, .. }, _) => {
Ok(Some((vec![FAT_PTR_ADDR as u32], vec![FAT_PTR_ADDR as u32])))
Ok(Some((layout.field_offset(tcx, FAT_PTR_ADDR, None),
Pointer,
vec![FAT_PTR_ADDR as u32])))
}
// Is this the NonZero lang item wrapping a pointer or integer type?
(&Univariant { non_zero: true, .. }, &ty::TyAdt(def, substs)) => {
let fields = &def.struct_variant().fields;
assert_eq!(fields.len(), 1);
match *fields[0].ty(tcx, substs).layout(tcx, param_env)? {
let field = fields[0].ty(tcx, substs).layout(tcx, param_env)?;
match *field {
// FIXME(eddyb) also allow floating-point types here.
Scalar { value: Int(_), non_zero: false } |
Scalar { value: Pointer, non_zero: false } => {
Ok(Some((vec![0], vec![0])))
Scalar { value: value @ Int(_), non_zero: false } |
Scalar { value: value @ Pointer, non_zero: false } => {
Ok(Some((layout.field_offset(tcx, 0, None),
value,
vec![0])))
}
FatPointer { non_zero: false, .. } => {
let tmp = vec![FAT_PTR_ADDR as u32, 0];
Ok(Some((tmp.clone(), tmp)))
Ok(Some((layout.field_offset(tcx, 0, None) +
field.field_offset(tcx, FAT_PTR_ADDR, None),
Pointer,
vec![FAT_PTR_ADDR as u32, 0])))
}
_ => Ok(None)
}
@ -878,31 +890,31 @@ impl<'a, 'tcx> Struct {
// Perhaps one of the fields of this struct is non-zero
// let's recurse and find out
(&Univariant { ref variant, .. }, &ty::TyAdt(def, substs)) if def.is_struct() => {
Struct::non_zero_field_paths(
Struct::non_zero_field(
tcx,
param_env,
def.struct_variant().fields.iter().map(|field| {
field.ty(tcx, substs)
}),
Some(&variant.memory_index[..]))
&variant.offsets)
}
// Perhaps one of the upvars of this closure is non-zero
(&Univariant { ref variant, .. }, &ty::TyClosure(def, substs)) => {
let upvar_tys = substs.upvar_tys(def, tcx);
Struct::non_zero_field_paths(
Struct::non_zero_field(
tcx,
param_env,
upvar_tys,
Some(&variant.memory_index[..]))
&variant.offsets)
}
// Can we use one of the fields in this tuple?
(&Univariant { ref variant, .. }, &ty::TyTuple(tys, _)) => {
Struct::non_zero_field_paths(
Struct::non_zero_field(
tcx,
param_env,
tys.iter().cloned(),
Some(&variant.memory_index[..]))
&variant.offsets)
}
// Is this a fixed-size array of something non-zero
@ -915,11 +927,11 @@ impl<'a, 'tcx> Struct {
}
}
if count.val.to_const_int().unwrap().to_u64().unwrap() != 0 {
Struct::non_zero_field_paths(
Struct::non_zero_field(
tcx,
param_env,
Some(ety).into_iter(),
None)
&[Size::from_bytes(0)])
} else {
Ok(None)
}
@ -938,27 +950,20 @@ impl<'a, 'tcx> Struct {
}
}
/// Find the path leading to a non-zero leaf field, starting from
/// Find the offset of a non-zero leaf field, starting from
/// the given set of fields and recursing through aggregates.
/// Returns Some((path, source_path)) on success.
/// `path` is translated to memory order. `source_path` is not.
fn non_zero_field_paths<I>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
/// Returns Some((offset, primitive, source_path)) on success.
fn non_zero_field<I>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
fields: I,
permutation: Option<&[u32]>)
-> Result<Option<(FieldPath, FieldPath)>, LayoutError<'tcx>>
offsets: &[Size])
-> Result<Option<(Size, Primitive, FieldPath)>, LayoutError<'tcx>>
where I: Iterator<Item=Ty<'tcx>> {
for (i, ty) in fields.enumerate() {
let r = Struct::non_zero_field_in_type(tcx, param_env, ty)?;
if let Some((mut path, mut source_path)) = r {
if let Some((offset, primitive, mut source_path)) = r {
source_path.push(i as u32);
let index = if let Some(p) = permutation {
p[i] as usize
} else {
i
};
path.push(index as u32);
return Ok(Some((path, source_path)));
return Ok(Some((offsets[i] + offset, primitive, source_path)));
}
}
Ok(None)
@ -1135,18 +1140,19 @@ pub enum Layout {
/// identity function.
RawNullablePointer {
nndiscr: u64,
value: Primitive
discr: Primitive
},
/// Two cases distinguished by a nullable pointer: the case with discriminant
/// `nndiscr` is represented by the struct `nonnull`, where the `discrfield`th
/// field is known to be nonnull due to its type; if that field is null, then
/// `nndiscr` is represented by the struct `nonnull`, where the field at the
/// `discr_offset` offset is known to be nonnull due to its type; if that field is null, then
/// it represents the other case, which is known to be zero sized.
StructWrappedNullablePointer {
nndiscr: u64,
nonnull: Struct,
discrfield: FieldPath,
/// Like discrfield, but in source order. For debuginfo.
discr: Primitive,
discr_offset: Size,
/// Like discr_offset, but the source field path. For debuginfo.
discrfield_source: FieldPath
}
}
@ -1440,44 +1446,36 @@ impl<'a, 'tcx> Layout {
if !Struct::would_be_zero_sized(dl, other_fields)? {
continue;
}
let paths = Struct::non_zero_field_paths(tcx,
param_env,
variants[discr].iter().cloned(),
None)?;
let (mut path, mut path_source) = if let Some(p) = paths { p }
else { continue };
// FIXME(eddyb) should take advantage of a newtype.
if path == &[0] && variants[discr].len() == 1 {
let value = match *variants[discr][0].layout(tcx, param_env)? {
Scalar { value, .. } => value,
CEnum { discr, .. } => Int(discr),
_ => bug!("Layout::compute: `{}`'s non-zero \
`{}` field not scalar?!",
ty, variants[discr][0])
};
return success(RawNullablePointer {
nndiscr: discr as u64,
value,
});
}
let st = Struct::new(dl,
&variants[discr].iter().map(|ty| ty.layout(tcx, param_env))
.collect::<Result<Vec<_>, _>>()?,
&def.repr, StructKind::AlwaysSizedUnivariant, ty)?;
// We have to fix the last element of path here.
let mut i = *path.last().unwrap();
i = st.memory_index[i as usize];
*path.last_mut().unwrap() = i;
path.reverse();
let field = Struct::non_zero_field(tcx,
param_env,
variants[discr].iter().cloned(),
&st.offsets)?;
let (offset, primitive, mut path_source) = if let Some(f) = field { f }
else { continue };
// FIXME(eddyb) should take advantage of a newtype.
if offset.bytes() == 0 && primitive.size(dl) == st.stride() &&
variants[discr].len() == 1 {
return success(RawNullablePointer {
nndiscr: discr as u64,
discr: primitive,
});
}
// We have to fix the source path here.
path_source.reverse();
return success(StructWrappedNullablePointer {
nndiscr: discr as u64,
nonnull: st,
discrfield: path,
discr: primitive,
discr_offset: offset,
discrfield_source: path_source
});
}
@ -1621,7 +1619,7 @@ impl<'a, 'tcx> Layout {
let dl = cx.data_layout();
match *self {
Scalar { value, .. } | RawNullablePointer { value, .. } => {
Scalar { value, .. } | RawNullablePointer { discr: value, .. } => {
value.size(dl)
}
@ -1664,7 +1662,7 @@ impl<'a, 'tcx> Layout {
let dl = cx.data_layout();
match *self {
Scalar { value, .. } | RawNullablePointer { value, .. } => {
Scalar { value, .. } | RawNullablePointer { discr: value, .. } => {
value.align(dl)
}
@ -1876,7 +1874,8 @@ impl<'a, 'tcx> Layout {
match *layout {
Layout::StructWrappedNullablePointer { nonnull: ref variant_layout,
nndiscr,
discrfield: _,
discr: _,
discr_offset: _,
discrfield_source: _ } => {
debug!("print-type-size t: `{:?}` adt struct-wrapped nullable nndiscr {} is {:?}",
ty, nndiscr, variant_layout);
@ -1891,12 +1890,12 @@ impl<'a, 'tcx> Layout {
&fields,
variant_layout)]);
}
Layout::RawNullablePointer { nndiscr, value } => {
Layout::RawNullablePointer { nndiscr, discr } => {
debug!("print-type-size t: `{:?}` adt raw nullable nndiscr {} is {:?}",
ty, nndiscr, value);
ty, nndiscr, discr);
let variant_def = &adt_def.variants[nndiscr as usize];
record(adt_kind.into(), None,
vec![build_primitive_info(variant_def.name, &value)]);
vec![build_primitive_info(variant_def.name, &discr)]);
}
Layout::Univariant { variant: ref variant_layout, non_zero: _ } => {
let variant_names = || {
@ -2410,19 +2409,21 @@ impl<'gcx> HashStable<StableHashingContext<'gcx>> for Layout
align.hash_stable(hcx, hasher);
primitive_align.hash_stable(hcx, hasher);
}
RawNullablePointer { nndiscr, ref value } => {
RawNullablePointer { nndiscr, ref discr } => {
nndiscr.hash_stable(hcx, hasher);
value.hash_stable(hcx, hasher);
discr.hash_stable(hcx, hasher);
}
StructWrappedNullablePointer {
nndiscr,
ref nonnull,
ref discrfield,
ref discr,
discr_offset,
ref discrfield_source
} => {
nndiscr.hash_stable(hcx, hasher);
nonnull.hash_stable(hcx, hasher);
discrfield.hash_stable(hcx, hasher);
discr.hash_stable(hcx, hasher);
discr_offset.hash_stable(hcx, hasher);
discrfield_source.hash_stable(hcx, hasher);
}
}

2
src/librustc_trans/abi.rs
View File

@ -295,7 +295,7 @@ impl<'tcx> LayoutExt<'tcx> for TyLayout<'tcx> {
match *self.layout {
// The primitives for this algorithm.
Layout::Scalar { value, .. } |
Layout::RawNullablePointer { value, .. } => {
Layout::RawNullablePointer { discr: value, .. } => {
let kind = match value {
layout::Int(_) |
layout::Pointer => RegKind::Integer,

2
src/librustc_trans/cabi_x86_64.rs
View File

@ -66,7 +66,7 @@ fn classify_arg<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, arg: &ArgType<'tcx>)
match *layout {
Layout::Scalar { value, .. } |
Layout::RawNullablePointer { value, .. } => {
Layout::RawNullablePointer { discr: value, .. } => {
let reg = match value {
layout::Int(_) |
layout::Pointer => Class::Int,

76
src/librustc_trans/mir/lvalue.rs
View File

@ -10,7 +10,7 @@
use llvm::{self, ValueRef};
use rustc::ty::{self, Ty, TypeFoldable};
use rustc::ty::layout::{self, Align, Layout, LayoutTyper};
use rustc::ty::layout::{self, Align, Layout, LayoutTyper, Size};
use rustc::mir;
use rustc::mir::tcx::LvalueTy;
use rustc_data_structures::indexed_vec::Idx;
@ -25,7 +25,6 @@ use type_::Type;
use value::Value;
use glue;
use std::iter;
use std::ptr;
use std::ops;
@ -330,14 +329,26 @@ impl<'a, 'tcx> LvalueRef<'tcx> {
}
}
// Double index to account for padding (FieldPath already uses `Struct::memory_index`)
fn gepi_struct_llfields_path(self, bcx: &Builder, discrfield: &layout::FieldPath) -> ValueRef {
let path = iter::once(C_u32(bcx.ccx, 0)).chain(discrfield.iter().map(|&i| {
let i = adt::memory_index_to_gep(i as u64);
assert_eq!(i as u32 as u64, i);
C_u32(bcx.ccx, i as u32)
})).collect::<Vec<_>>();
bcx.inbounds_gep(self.llval, &path)
// Return a pointer to the discriminant, given its type and offset.
fn gepi_discr_at_offset(self, bcx: &Builder,
discr: ty::layout::Primitive,
offset: Size)
-> (ValueRef, Alignment) {
let size = discr.size(bcx.ccx);
let ptr_ty = Type::from_primitive(bcx.ccx, discr).ptr_to();
// If the discriminant is not on a multiple of the primitive's size,
// we need to go through i8*. Also assume the worst alignment.
if offset.bytes() % size.bytes() != 0 {
let byte_ptr = bcx.pointercast(self.llval, Type::i8p(bcx.ccx));
let byte_ptr = bcx.inbounds_gep(byte_ptr, &[C_usize(bcx.ccx, offset.bytes())]);
let byte_align = Alignment::Packed(Align::from_bytes(1, 1).unwrap());
return (bcx.pointercast(byte_ptr, ptr_ty), byte_align);
}
let discr_ptr = bcx.pointercast(self.llval, ptr_ty);
(bcx.inbounds_gep(discr_ptr, &[C_usize(bcx.ccx, offset.bytes() / size.bytes())]),
self.alignment)
}
/// Helper for cases where the discriminant is simply loaded.
@ -378,16 +389,16 @@ impl<'a, 'tcx> LvalueRef<'tcx> {
self.load_discr(bcx, discr, ptr.llval, 0, variants.len() as u64 - 1)
}
layout::Univariant { .. } | layout::UntaggedUnion { .. } => C_u8(bcx.ccx, 0),
layout::RawNullablePointer { nndiscr, .. } => {
layout::RawNullablePointer { nndiscr, discr } |
layout::StructWrappedNullablePointer { nndiscr, discr, .. } => {
let discr_offset = match *l {
layout::StructWrappedNullablePointer { discr_offset, .. } => discr_offset,
_ => Size::from_bytes(0),
};
let (lldiscrptr, alignment) = self.gepi_discr_at_offset(bcx, discr, discr_offset);
let lldiscr = bcx.load(lldiscrptr, alignment.non_abi());
let cmp = if nndiscr == 0 { llvm::IntEQ } else { llvm::IntNE };
let discr = bcx.load(self.llval, self.alignment.non_abi());
bcx.icmp(cmp, discr, C_null(val_ty(discr)))
}
layout::StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
let llptrptr = self.gepi_struct_llfields_path(bcx, discrfield);
let llptr = bcx.load(llptrptr, self.alignment.non_abi());
let cmp = if nndiscr == 0 { llvm::IntEQ } else { llvm::IntNE };
bcx.icmp(cmp, llptr, C_null(val_ty(llptr)))
bcx.icmp(cmp, lldiscr, C_null(Type::from_primitive(bcx.ccx, discr)))
},
_ => bug!("{} is not an enum", l.ty)
};
@ -418,27 +429,30 @@ impl<'a, 'tcx> LvalueRef<'tcx> {
| layout::Vector { .. } => {
assert_eq!(to, 0);
}
layout::RawNullablePointer { nndiscr, .. } => {
layout::RawNullablePointer { nndiscr, discr, .. } |
layout::StructWrappedNullablePointer { nndiscr, discr, .. } => {
if to != nndiscr {
let llptrty = val_ty(self.llval).element_type();
bcx.store(C_null(llptrty), self.llval, self.alignment.non_abi());
let (use_memset, discr_offset) = match *l {
layout::StructWrappedNullablePointer { discr_offset, .. } => {
(target_sets_discr_via_memset(bcx), discr_offset)
}
}
layout::StructWrappedNullablePointer { nndiscr, ref discrfield, ref nonnull, .. } => {
if to != nndiscr {
if target_sets_discr_via_memset(bcx) {
_ => (false, Size::from_bytes(0)),
};
if use_memset {
// Issue #34427: As workaround for LLVM bug on
// ARM, use memset of 0 on whole struct rather
// than storing null to single target field.
let llptr = bcx.pointercast(self.llval, Type::i8(bcx.ccx).ptr_to());
let fill_byte = C_u8(bcx.ccx, 0);
let size = C_usize(bcx.ccx, nonnull.stride().bytes());
let align = C_u32(bcx.ccx, nonnull.align.abi() as u32);
let (size, align) = l.size_and_align(bcx.ccx);
let size = C_usize(bcx.ccx, size.bytes());
let align = C_u32(bcx.ccx, align.abi() as u32);
base::call_memset(bcx, llptr, fill_byte, size, align, false);
} else {
let llptrptr = self.gepi_struct_llfields_path(bcx, discrfield);
let llptrty = val_ty(llptrptr).element_type();
bcx.store(C_null(llptrty), llptrptr, self.alignment.non_abi());
let (lldiscrptr, alignment) =
self.gepi_discr_at_offset(bcx, discr, discr_offset);
bcx.store(C_null(Type::from_primitive(bcx.ccx, discr)),
lldiscrptr, alignment.non_abi());
}
}
}

10
src/librustc_trans/type_.rs
View File

@ -287,4 +287,14 @@ impl Type {
I128 => Type::i128(cx),
}
}
pub fn from_primitive(cx: &CrateContext, p: layout::Primitive) -> Type {
use rustc::ty::layout::Primitive::*;
match p {
Int(i) => Type::from_integer(cx, i),
F32 => Type::f32(cx),
F64 => Type::f64(cx),
Pointer => Type::i8p(cx),
}
}
}

1
src/test/ui/print_type_sizes/nullable.stdout
View File

@ -19,6 +19,5 @@ print-type-size field `.pre`: 1 bytes
print-type-size end padding: 1 bytes
print-type-size type: `MyOption<core::nonzero::NonZero<u32>>`: 4 bytes, alignment: 4 bytes
print-type-size variant `Some`: 4 bytes
print-type-size field `.0`: 4 bytes
print-type-size type: `core::nonzero::NonZero<u32>`: 4 bytes, alignment: 4 bytes
print-type-size field `.0`: 4 bytes