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Add !nonnull metadata to loads from fat pointers
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The data pointer inside a safe fat pointer is never null. The same is
true for the vtable pointer inside a fat pointer for a trait object.
Wrapping loads/stores of the components of a fat pointer in functions
allows to easily make sure that we emit the appropriate metadata and
allow LLVM to perform better optimizations.
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@dotdash
dotdash committed Jul 22, 2015
1 parent 9090420 commit e8f5955
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Showing 11 changed files with 94 additions and 68 deletions.
9 changes: 9 additions & 0 deletions src/librustc/middle/ty.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3850,6 +3850,15 @@ impl<'tcx> TyS<'tcx> {
}
}

pub fn pointee_type(&self, cx: &ctxt<'tcx>) -> Ty<'tcx> {
match self.sty {
ty::TyBox(inner) |
ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) |
ty::TyRawPtr(ty::TypeAndMut { ty: inner, .. }) => inner,
_ => cx.sess.bug(&format!("pointee_type called on non-pointer value: {}", self))
}
}

pub fn sequence_element_type(&self, cx: &ctxt<'tcx>) -> Ty<'tcx> {
match self.sty {
TyArray(ty, _) | TySlice(ty) => ty,
Expand Down
35 changes: 17 additions & 18 deletions src/librustc_trans/trans/_match.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -188,7 +188,6 @@ pub use self::TransBindingMode::*;
use self::Opt::*;
use self::FailureHandler::*;

use back::abi;
use llvm::{ValueRef, BasicBlockRef};
use middle::check_match::StaticInliner;
use middle::check_match;
Expand Down Expand Up @@ -678,9 +677,8 @@ fn bind_subslice_pat(bcx: Block,
let slice_ty = bcx.tcx().mk_imm_ref(bcx.tcx().mk_region(ty::ReStatic),
bcx.tcx().mk_slice(unit_ty));
let scratch = rvalue_scratch_datum(bcx, slice_ty, "");
Store(bcx, slice_begin,
GEPi(bcx, scratch.val, &[0, abi::FAT_PTR_ADDR]));
Store(bcx, slice_len, GEPi(bcx, scratch.val, &[0, abi::FAT_PTR_EXTRA]));
store_addr(bcx, slice_begin, scratch.val);
store_extra(bcx, slice_len, scratch.val);
scratch.val
}

Expand Down Expand Up @@ -833,10 +831,11 @@ fn compare_values<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
None,
&format!("comparison of `{}`", rhs_t),
StrEqFnLangItem);
let lhs_data = Load(cx, expr::get_dataptr(cx, lhs));
let lhs_len = Load(cx, expr::get_len(cx, lhs));
let rhs_data = Load(cx, expr::get_dataptr(cx, rhs));
let rhs_len = Load(cx, expr::get_len(cx, rhs));
let str_ty = cx.tcx().mk_str();
let lhs_data = load_addr(cx, lhs);
let lhs_len = load_extra(cx, lhs, str_ty);
let rhs_data = load_addr(cx, rhs);
let rhs_len = load_extra(cx, rhs, str_ty);
callee::trans_lang_call(cx, did, &[lhs_data, lhs_len, rhs_data, rhs_len], None, debug_loc)
}

Expand All @@ -857,15 +856,15 @@ fn compare_values<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
let ty_str_slice = cx.tcx().mk_static_str();

let rhs_str = alloc_ty(cx, ty_str_slice, "rhs_str");
Store(cx, GEPi(cx, rhs, &[0, 0]), expr::get_dataptr(cx, rhs_str));
Store(cx, C_uint(cx.ccx(), pat_len), expr::get_len(cx, rhs_str));
store_addr(cx, GEPi(cx, rhs, &[0, 0]), rhs_str);
store_extra(cx, C_uint(cx.ccx(), pat_len), rhs_str);

let lhs_str;
if val_ty(lhs) == val_ty(rhs) {
// Both the discriminant and the pattern are thin pointers
lhs_str = alloc_ty(cx, ty_str_slice, "lhs_str");
Store(cx, GEPi(cx, lhs, &[0, 0]), expr::get_dataptr(cx, lhs_str));
Store(cx, C_uint(cx.ccx(), pat_len), expr::get_len(cx, lhs_str));
store_addr(cx, GEPi(cx, lhs, &[0, 0]), lhs_str);
store_extra(cx, C_uint(cx.ccx(), pat_len), lhs_str);
}
else {
// The discriminant is a fat pointer
Expand Down Expand Up @@ -1016,7 +1015,7 @@ fn compile_submatch<'a, 'p, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
let binfo = *data.bindings_map.get(ident).unwrap();
call_lifetime_start(bcx, binfo.llmatch);
if binfo.trmode == TrByRef && type_is_fat_ptr(bcx.tcx(), binfo.ty) {
expr::copy_fat_ptr(bcx, *value_ptr, binfo.llmatch);
expr::copy_fat_ptr(bcx, *value_ptr, binfo.llmatch, binfo.ty);
}
else {
Store(bcx, *value_ptr, binfo.llmatch);
Expand Down Expand Up @@ -1080,7 +1079,7 @@ fn compile_submatch_continue<'a, 'p, 'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
// the last field specially: instead of simply passing a
// ValueRef pointing to that field, as with all the others,
// we skip it and instead construct a 'fat ptr' below.
(arg_count - 1, Load(bcx, expr::get_dataptr(bcx, val)))
(arg_count - 1, load_addr(bcx, val))
};
let mut field_vals: Vec<ValueRef> = (0..arg_count).map(|ix|
adt::trans_field_ptr(bcx, &*repr, struct_val, 0, ix)
Expand All @@ -1099,9 +1098,9 @@ fn compile_submatch_continue<'a, 'p, 'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
let llty = type_of::type_of(bcx.ccx(), unsized_ty);
let scratch = alloca_no_lifetime(bcx, llty, "__struct_field_fat_ptr");
let data = adt::trans_field_ptr(bcx, &*repr, struct_val, 0, arg_count);
let len = Load(bcx, expr::get_len(bcx, val));
Store(bcx, data, expr::get_dataptr(bcx, scratch));
Store(bcx, len, expr::get_len(bcx, scratch));
let len = load_extra(bcx, val, left_ty);
store_addr(bcx, data, scratch);
store_extra(bcx, len, scratch);
field_vals.push(scratch);
}
_ => {}
Expand Down Expand Up @@ -1681,7 +1680,7 @@ pub fn bind_irrefutable_pat<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
// By ref binding: the value of the variable
// is the pointer `val` itself or fat pointer referenced by `val`
if type_is_fat_ptr(bcx.tcx(), ty) {
expr::copy_fat_ptr(bcx, val, llval);
expr::copy_fat_ptr(bcx, val, llval, ty);
}
else {
Store(bcx, val, llval);
Expand Down
45 changes: 32 additions & 13 deletions src/librustc_trans/trans/base.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -408,9 +408,7 @@ pub fn iter_structural_ty<'blk, 'tcx, F>(cx: Block<'blk, 'tcx>,
let (data_ptr, info) = if common::type_is_sized(cx.tcx(), t) {
(av, None)
} else {
let data = GEPi(cx, av, &[0, abi::FAT_PTR_ADDR]);
let info = GEPi(cx, av, &[0, abi::FAT_PTR_EXTRA]);
(Load(cx, data), Some(Load(cx, info)))
(load_addr(cx, av), Some(load_extra(cx, av, t)))
};

let mut cx = cx;
Expand All @@ -426,8 +424,8 @@ pub fn iter_structural_ty<'blk, 'tcx, F>(cx: Block<'blk, 'tcx>,
llfld_a
} else {
let scratch = datum::rvalue_scratch_datum(cx, field_ty, "__fat_ptr_iter");
Store(cx, llfld_a, GEPi(cx, scratch.val, &[0, abi::FAT_PTR_ADDR]));
Store(cx, info.unwrap(), GEPi(cx, scratch.val, &[0, abi::FAT_PTR_EXTRA]));
store_addr(cx, llfld_a, scratch.val);
store_extra(cx, info.unwrap(), scratch.val);
scratch.val
};
cx = f(cx, val, field_ty);
Expand Down Expand Up @@ -777,6 +775,27 @@ pub fn load_if_immediate<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
return v;
}

pub fn load_addr(bcx: Block, fatptr: ValueRef) -> ValueRef {
LoadNonNull(bcx, expr::get_dataptr(bcx, fatptr))
}

pub fn store_addr(bcx: Block, addr: ValueRef, fatptr: ValueRef) -> ValueRef {
Store(bcx, addr, expr::get_dataptr(bcx, fatptr))
}

pub fn load_extra<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, fatptr: ValueRef, ty: Ty<'tcx>) -> ValueRef {
assert!(!common::type_is_sized(bcx.tcx(), ty));
if ty.is_trait() {
LoadNonNull(bcx, expr::get_len(bcx, fatptr))
} else {
Load(bcx, expr::get_len(bcx, fatptr))
}
}

pub fn store_extra(bcx: Block, extra: ValueRef, fatptr: ValueRef) -> ValueRef {
Store(bcx, extra, expr::get_len(bcx, fatptr))
}

/// Helper for loading values from memory. Does the necessary conversion if the in-memory type
/// differs from the type used for SSA values. Also handles various special cases where the type
/// gives us better information about what we are loading.
Expand Down Expand Up @@ -835,8 +854,8 @@ pub fn store_ty<'blk, 'tcx>(cx: Block<'blk, 'tcx>, v: ValueRef, dst: ValueRef, t
}

if common::type_is_fat_ptr(cx.tcx(), t) {
Store(cx, ExtractValue(cx, v, abi::FAT_PTR_ADDR), expr::get_dataptr(cx, dst));
Store(cx, ExtractValue(cx, v, abi::FAT_PTR_EXTRA), expr::get_len(cx, dst));
store_addr(cx, ExtractValue(cx, v, abi::FAT_PTR_ADDR), dst);
store_extra(cx, ExtractValue(cx, v, abi::FAT_PTR_EXTRA), dst);
} else {
let store = Store(cx, from_arg_ty(cx, v, t), to_arg_ty_ptr(cx, dst, t));
unsafe {
Expand Down Expand Up @@ -1348,8 +1367,8 @@ pub fn create_datums_for_fn_args<'a, 'tcx>(mut bcx: Block<'a, 'tcx>,
unpack_datum!(bcx, datum::lvalue_scratch_datum(bcx, arg_ty, "",
arg_scope_id, (data, extra),
|(data, extra), bcx, dst| {
Store(bcx, data, expr::get_dataptr(bcx, dst));
Store(bcx, extra, expr::get_len(bcx, dst));
store_addr(bcx, data, dst);
store_extra(bcx, extra, dst);
bcx
}))
} else {
Expand Down Expand Up @@ -1379,8 +1398,8 @@ pub fn create_datums_for_fn_args<'a, 'tcx>(mut bcx: Block<'a, 'tcx>,
if common::type_is_fat_ptr(bcx.tcx(), tupled_arg_ty) {
let data = get_param(bcx.fcx.llfn, idx);
let extra = get_param(bcx.fcx.llfn, idx + 1);
Store(bcx, data, expr::get_dataptr(bcx, lldest));
Store(bcx, extra, expr::get_len(bcx, lldest));
store_addr(bcx, data, lldest);
store_extra(bcx, extra, lldest);
idx += 2;
} else {
let datum = datum::Datum::new(
Expand Down Expand Up @@ -1784,8 +1803,8 @@ fn trans_enum_variant_or_tuple_like_struct<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx
disr,
i);
if common::type_is_fat_ptr(bcx.tcx(), arg_ty) {
Store(bcx, get_param(fcx.llfn, llarg_idx), expr::get_dataptr(bcx, lldestptr));
Store(bcx, get_param(fcx.llfn, llarg_idx + 1), expr::get_len(bcx, lldestptr));
store_addr(bcx, get_param(fcx.llfn, llarg_idx), lldestptr);
store_extra(bcx, get_param(fcx.llfn, llarg_idx + 1), lldestptr);
llarg_idx += 2;
} else {
let arg = get_param(fcx.llfn, llarg_idx);
Expand Down
5 changes: 3 additions & 2 deletions src/librustc_trans/trans/callee.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1123,8 +1123,9 @@ pub fn trans_arg_datum<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
debug!("--- trans_arg_datum passing {}", bcx.val_to_string(val));

if common::type_is_fat_ptr(bcx.tcx(), formal_arg_ty) {
llargs.push(Load(bcx, expr::get_dataptr(bcx, val)));
llargs.push(Load(bcx, expr::get_len(bcx, val)));
let ty = formal_arg_ty.pointee_type(bcx.tcx());
llargs.push(load_addr(bcx, val));
llargs.push(load_extra(bcx, val, ty));
} else {
llargs.push(val);
}
Expand Down
3 changes: 1 addition & 2 deletions src/librustc_trans/trans/datum.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,6 @@ pub use self::RvalueMode::*;

use llvm::ValueRef;
use trans::base::*;
use trans::build::Load;
use trans::common::*;
use trans::cleanup;
use trans::cleanup::CleanupMethods;
Expand Down Expand Up @@ -524,7 +523,7 @@ impl<'tcx> Datum<'tcx, Lvalue> {
let val = if type_is_sized(bcx.tcx(), self.ty) {
gep(self.val)
} else {
gep(Load(bcx, expr::get_dataptr(bcx, self.val)))
gep(load_addr(bcx, self.val))
};
Datum {
val: val,
Expand Down
26 changes: 15 additions & 11 deletions src/librustc_trans/trans/expr.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -290,9 +290,13 @@ pub fn get_dataptr(bcx: Block, fat_ptr: ValueRef) -> ValueRef {
GEPi(bcx, fat_ptr, &[0, abi::FAT_PTR_ADDR])
}

pub fn copy_fat_ptr(bcx: Block, src_ptr: ValueRef, dst_ptr: ValueRef) {
Store(bcx, Load(bcx, get_dataptr(bcx, src_ptr)), get_dataptr(bcx, dst_ptr));
Store(bcx, Load(bcx, get_len(bcx, src_ptr)), get_len(bcx, dst_ptr));
pub fn copy_fat_ptr<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
src_ptr: ValueRef,
dst_ptr: ValueRef,
ty: Ty<'tcx>) {
let pointee_ty = ty.pointee_type(bcx.tcx());
store_addr(bcx, load_addr(bcx, src_ptr), dst_ptr);

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@arielb1

arielb1 Jul 22, 2015

This emits !notnull metadata on the pointer. Are you sure it's only used when the pointer is dereferencable?
store_extra(bcx, load_extra(bcx, src_ptr, pointee_ty), dst_ptr);
}

/// Retrieve the information we are losing (making dynamic) in an unsizing
Expand Down Expand Up @@ -453,8 +457,8 @@ fn coerce_unsized<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
// to use a different vtable. In that case, we want to
// load out the original data pointer so we can repackage
// it.
(Load(bcx, get_dataptr(bcx, source.val)),
Some(Load(bcx, get_len(bcx, source.val))))
(load_addr(bcx, source.val),
Some(load_extra(bcx, source.val, inner_source)))
} else {
let val = if source.kind.is_by_ref() {
load_ty(bcx, source.val, source.ty)
Expand All @@ -472,8 +476,8 @@ fn coerce_unsized<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
let ptr_ty = type_of::in_memory_type_of(bcx.ccx(), inner_target).ptr_to();
let base = PointerCast(bcx, base, ptr_ty);

Store(bcx, base, get_dataptr(bcx, target.val));
Store(bcx, info, get_len(bcx, target.val));
store_addr(bcx, base, target.val);
store_extra(bcx, info, target.val);
}

// This can be extended to enums and tuples in the future.
Expand Down Expand Up @@ -727,9 +731,9 @@ fn trans_field<'blk, 'tcx, F>(bcx: Block<'blk, 'tcx>,
DatumBlock { datum: d.to_expr_datum(), bcx: bcx }
} else {
let scratch = rvalue_scratch_datum(bcx, d.ty, "");
Store(bcx, d.val, get_dataptr(bcx, scratch.val));
let info = Load(bcx, get_len(bcx, base_datum.val));
Store(bcx, info, get_len(bcx, scratch.val));
store_addr(bcx, d.val, scratch.val);
let info = load_extra(bcx, base_datum.val, d.ty);
store_extra(bcx, info, scratch.val);

// Always generate an lvalue datum, because this pointer doesn't own
// the data and cleanup is scheduled elsewhere.
Expand Down Expand Up @@ -2083,7 +2087,7 @@ fn trans_imm_cast<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
// Return the address
return immediate_rvalue_bcx(bcx,
PointerCast(bcx,
Load(bcx, get_dataptr(bcx, datum.val)),
load_addr(bcx, datum.val),
ll_t_out),
t_out).to_expr_datumblock();
}
Expand Down
5 changes: 2 additions & 3 deletions src/librustc_trans/trans/foreign.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,6 @@ use trans::cabi;
use trans::common::*;
use trans::debuginfo::DebugLoc;
use trans::declare;
use trans::expr;
use trans::machine;
use trans::monomorphize;
use trans::type_::Type;
Expand Down Expand Up @@ -298,8 +297,8 @@ pub fn trans_native_call<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
type_of::type_of(ccx, passed_arg_tys[i]),
"__arg");
if type_is_fat_ptr(ccx.tcx(), passed_arg_tys[i]) {
Store(bcx, llargs_rust[i + offset], expr::get_dataptr(bcx, scratch));
Store(bcx, llargs_rust[i + offset + 1], expr::get_len(bcx, scratch));
base::store_addr(bcx, llargs_rust[i + offset], scratch);
base::store_extra(bcx, llargs_rust[i + offset + 1], scratch);
offset += 1;
} else {
base::store_ty(bcx, llarg_rust, scratch, passed_arg_tys[i]);
Expand Down
14 changes: 5 additions & 9 deletions src/librustc_trans/trans/glue.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,6 @@
// Code relating to drop glue.


use back::abi;
use back::link::*;
use llvm;
use llvm::{ValueRef, get_param};
Expand Down Expand Up @@ -374,7 +373,7 @@ fn trans_struct_drop<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
let (_, bcx) = if type_is_sized(bcx.tcx(), t) {
invoke(bcx, dtor_addr, &[v0], dtor_ty, DebugLoc::None)
} else {
let args = [Load(bcx, expr::get_dataptr(bcx, v0)), Load(bcx, expr::get_len(bcx, v0))];
let args = [load_addr(bcx, v0), load_extra(bcx, v0, t)];
invoke(bcx, dtor_addr, &args, dtor_ty, DebugLoc::None)
};

Expand Down Expand Up @@ -465,15 +464,13 @@ fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, g: DropGlueK
// a safe-guard, assert TyBox not used with TyContents.
assert!(!skip_dtor);
if !type_is_sized(bcx.tcx(), content_ty) {
let llval = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
let llbox = Load(bcx, llval);
let llbox = load_addr(bcx, v0);
let llbox_as_usize = PtrToInt(bcx, llbox, Type::int(bcx.ccx()));
let drop_flag_not_dropped_already =
ICmp(bcx, llvm::IntNE, llbox_as_usize, dropped_pattern, DebugLoc::None);
with_cond(bcx, drop_flag_not_dropped_already, |bcx| {
let bcx = drop_ty(bcx, v0, content_ty, DebugLoc::None);
let info = GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]);
let info = Load(bcx, info);
let info = load_extra(bcx, v0, content_ty);
let (llsize, llalign) = size_and_align_of_dst(bcx, content_ty, info);

// `Box<ZeroSizeType>` does not allocate.
Expand Down Expand Up @@ -531,12 +528,11 @@ fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, g: DropGlueK
// versus without calling Drop::drop. Assert caller is
// okay with always calling the Drop impl, if any.
assert!(!skip_dtor);
let data_ptr = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
let vtable_ptr = Load(bcx, GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]));
let vtable_ptr = load_extra(bcx, v0, t);
let dtor = Load(bcx, vtable_ptr);
Call(bcx,
dtor,
&[PointerCast(bcx, Load(bcx, data_ptr), Type::i8p(bcx.ccx()))],
&[PointerCast(bcx, load_addr(bcx, v0), Type::i8p(bcx.ccx()))],
None,
DebugLoc::None);
bcx
Expand Down
4 changes: 2 additions & 2 deletions src/librustc_trans/trans/intrinsic.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -397,8 +397,8 @@ pub fn trans_intrinsic_call<'a, 'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
llargs[0]
} else {
let scratch = rvalue_scratch_datum(bcx, tp_ty, "tmp");
Store(bcx, llargs[0], expr::get_dataptr(bcx, scratch.val));
Store(bcx, llargs[1], expr::get_len(bcx, scratch.val));
store_addr(bcx, llargs[0], scratch.val);
store_extra(bcx, llargs[1], scratch.val);
fcx.schedule_lifetime_end(cleanup::CustomScope(cleanup_scope), scratch.val);
scratch.val
};
Expand Down
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