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Fix: ices on virtual-function-elimination about principal trait #130734

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merged 1 commit into from
Sep 25, 2024
Merged

Fix: ices on virtual-function-elimination about principal trait #130734

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9 changes: 2 additions & 7 deletions compiler/rustc_codegen_ssa/src/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,7 @@ use crate::back::write::{
submit_post_lto_module_to_llvm, submit_pre_lto_module_to_llvm, ComputedLtoType, OngoingCodegen,
};
use crate::common::{self, IntPredicate, RealPredicate, TypeKind};
use crate::meth::load_vtable;
use crate::mir::operand::OperandValue;
use crate::mir::place::PlaceRef;
use crate::traits::*;
Expand Down Expand Up @@ -135,14 +136,8 @@ fn unsized_info<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(

if let Some(entry_idx) = vptr_entry_idx {
let ptr_size = bx.data_layout().pointer_size;
let ptr_align = bx.data_layout().pointer_align.abi;
let vtable_byte_offset = u64::try_from(entry_idx).unwrap() * ptr_size.bytes();
let gep = bx.inbounds_ptradd(old_info, bx.const_usize(vtable_byte_offset));
let new_vptr = bx.load(bx.type_ptr(), gep, ptr_align);
bx.nonnull_metadata(new_vptr);
// VTable loads are invariant.
bx.set_invariant_load(new_vptr);
new_vptr
load_vtable(bx, old_info, bx.type_ptr(), vtable_byte_offset, source, true)
} else {
old_info
}
Expand Down
67 changes: 39 additions & 28 deletions compiler/rustc_codegen_ssa/src/meth.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,27 +28,9 @@ impl<'a, 'tcx> VirtualIndex {

let llty = bx.fn_ptr_backend_type(fn_abi);
let ptr_size = bx.data_layout().pointer_size;
let ptr_align = bx.data_layout().pointer_align.abi;
let vtable_byte_offset = self.0 * ptr_size.bytes();

if bx.cx().sess().opts.unstable_opts.virtual_function_elimination
&& bx.cx().sess().lto() == Lto::Fat
{
let typeid = bx
.typeid_metadata(typeid_for_trait_ref(bx.tcx(), expect_dyn_trait_in_self(ty)))
.unwrap();
let func = bx.type_checked_load(llvtable, vtable_byte_offset, typeid);
func
} else {
let gep = bx.inbounds_ptradd(llvtable, bx.const_usize(vtable_byte_offset));
let ptr = bx.load(llty, gep, ptr_align);
// VTable loads are invariant.
bx.set_invariant_load(ptr);
if nonnull {
bx.nonnull_metadata(ptr);
}
ptr
}
load_vtable(bx, llvtable, llty, vtable_byte_offset, ty, nonnull)
}

pub(crate) fn get_optional_fn<Bx: BuilderMethods<'a, 'tcx>>(
Expand All @@ -75,31 +57,27 @@ impl<'a, 'tcx> VirtualIndex {
self,
bx: &mut Bx,
llvtable: Bx::Value,
ty: Ty<'tcx>,
) -> Bx::Value {
// Load the data pointer from the object.
debug!("get_int({:?}, {:?})", llvtable, self);

let llty = bx.type_isize();
let ptr_size = bx.data_layout().pointer_size;
let ptr_align = bx.data_layout().pointer_align.abi;
let vtable_byte_offset = self.0 * ptr_size.bytes();

let gep = bx.inbounds_ptradd(llvtable, bx.const_usize(vtable_byte_offset));
let ptr = bx.load(llty, gep, ptr_align);
// VTable loads are invariant.
bx.set_invariant_load(ptr);
ptr
load_vtable(bx, llvtable, llty, vtable_byte_offset, ty, false)
}
}

/// This takes a valid `self` receiver type and extracts the principal trait
/// ref of the type.
fn expect_dyn_trait_in_self(ty: Ty<'_>) -> ty::PolyExistentialTraitRef<'_> {
/// ref of the type. Return `None` if there is no principal trait.
fn dyn_trait_in_self(ty: Ty<'_>) -> Option<ty::PolyExistentialTraitRef<'_>> {
for arg in ty.peel_refs().walk() {
if let GenericArgKind::Type(ty) = arg.unpack()
&& let ty::Dynamic(data, _, _) = ty.kind()
{
return data.principal().expect("expected principal trait object");
return data.principal();
}
}

Expand Down Expand Up @@ -138,3 +116,36 @@ pub(crate) fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
cx.vtables().borrow_mut().insert((ty, trait_ref), vtable);
vtable
}

/// Call this function whenever you need to load a vtable.
pub(crate) fn load_vtable<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
bx: &mut Bx,
llvtable: Bx::Value,
llty: Bx::Type,
vtable_byte_offset: u64,
ty: Ty<'tcx>,
nonnull: bool,
) -> Bx::Value {
let ptr_align = bx.data_layout().pointer_align.abi;

if bx.cx().sess().opts.unstable_opts.virtual_function_elimination
&& bx.cx().sess().lto() == Lto::Fat
{
if let Some(trait_ref) = dyn_trait_in_self(ty) {
let typeid = bx.typeid_metadata(typeid_for_trait_ref(bx.tcx(), trait_ref)).unwrap();
let func = bx.type_checked_load(llvtable, vtable_byte_offset, typeid);
return func;
} else if nonnull {
bug!("load nonnull value from a vtable without a principal trait")
}
}

let gep = bx.inbounds_ptradd(llvtable, bx.const_usize(vtable_byte_offset));
let ptr = bx.load(llty, gep, ptr_align);
// VTable loads are invariant.
bx.set_invariant_load(ptr);
if nonnull {
bx.nonnull_metadata(ptr);
}
ptr
}
2 changes: 1 addition & 1 deletion compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -126,7 +126,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
sym::vtable_align => ty::COMMON_VTABLE_ENTRIES_ALIGN,
_ => bug!(),
};
let value = meth::VirtualIndex::from_index(idx).get_usize(bx, vtable);
let value = meth::VirtualIndex::from_index(idx).get_usize(bx, vtable, callee_ty);
match name {
// Size is always <= isize::MAX.
sym::vtable_size => {
Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_codegen_ssa/src/size_of_val.rs
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Expand Up @@ -28,9 +28,9 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
// Load size/align from vtable.
let vtable = info.unwrap();
let size = meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_SIZE)
.get_usize(bx, vtable);
.get_usize(bx, vtable, t);
let align = meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_ALIGN)
.get_usize(bx, vtable);
.get_usize(bx, vtable, t);

// Size is always <= isize::MAX.
let size_bound = bx.data_layout().ptr_sized_integer().signed_max() as u128;
Expand Down
6 changes: 0 additions & 6 deletions tests/crashes/123955.rs
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7 changes: 0 additions & 7 deletions tests/crashes/124092.rs
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17 changes: 17 additions & 0 deletions tests/ui/codegen/virtual-function-elimination.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
//@ build-pass
//@ compile-flags: -Zvirtual-function-elimination=true -Clto=true
//@ only-x86_64
//@ no-prefer-dynamic
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why is this argument needed?

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./x test needs this argument to perform LTO.
Below is the error message without no-prefer-dynamic:

running 1 tests

[ui] tests/ui/codegen/virtual-function-elimination.rs ... F


failures:

---- [ui] tests/ui/codegen/virtual-function-elimination.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/home/ray/Desktop/rust/build/x86_64-unknown-linux-gnu/stage1/bin/rustc" "/home/ray/Desktop/rust/tests/ui/codegen/virtual-function-elimination.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/home/ray/.cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/home/ray/Desktop/rust/vendor" "--sysroot" "/home/ray/Desktop/rust/build/x86_64-unknown-linux-gnu/stage1" "--target=x86_64-unknown-linux-gnu" "--check-cfg" "cfg(FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "-C" "prefer-dynamic" "--out-dir" "/home/ray/Desktop/rust/build/x86_64-unknown-linux-gnu/test/ui/codegen/virtual-function-elimination" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-Lnative=/home/ray/Desktop/rust/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/home/ray/Desktop/rust/build/x86_64-unknown-linux-gnu/test/ui/codegen/virtual-function-elimination/auxiliary" "-Zvirtual-function-elimination=true" "-Clto=true"
stdout: none
--- stderr -------------------------------
error: cannot prefer dynamic linking when performing LTO
   |
   = note: only 'staticlib', 'bin', and 'cdylib' outputs are supported with LTO

error: aborting due to 1 previous error
------------------------------------------


// issue #123955
pub fn test0() {
_ = Box::new(()) as Box<dyn Send>;
}

// issue #124092
const X: for<'b> fn(&'b ()) = |&()| ();
pub fn test1() {
let _dyn_debug = Box::new(X) as Box<fn(&'static ())> as Box<dyn Send>;
}

fn main() {}
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