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rust-bors merged 2 commits into from
Jun 25, 2026
+212 −228
Merged

autodiff - typtree cleanups #158278

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b9d55eb
move typetree logic into a new file
ZuseZ4 Jun 22, 2026
d9038db
simplify call chains, fix assertions
ZuseZ4 Jun 23, 2026
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3 changes: 2 additions & 1 deletion compiler/rustc_codegen_llvm/src/intrinsic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@ use crate::errors::{
AutoDiffWithoutEnable, AutoDiffWithoutLto, IntrinsicSignatureMismatch, IntrinsicWrongArch,
OffloadWithoutEnable, OffloadWithoutFatLTO, UnknownIntrinsic,
};
use crate::intrinsic::ty::typetree::fnc_typetrees;
use crate::llvm::{self, Type, Value};
use crate::type_of::LayoutLlvmExt;
use crate::va_arg::emit_va_arg;
Expand Down Expand Up @@ -1791,7 +1792,7 @@ fn codegen_autodiff<'ll, 'tcx>(
&mut diff_attrs.input_activity,
);

let fnc_tree = rustc_middle::ty::fnc_typetrees(tcx, source_fn_ptr_ty);
let fnc_tree = fnc_typetrees(tcx, source_fn_ptr_ty);

// Build body
generate_enzyme_call(
Expand Down
229 changes: 2 additions & 227 deletions compiler/rustc_middle/src/ty/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,6 @@ pub use intrinsic::IntrinsicDef;
use rustc_abi::{
Align, FieldIdx, Integer, IntegerType, ReprFlags, ReprOptions, ScalableElt, VariantIdx,
};
use rustc_ast::expand::typetree::{FncTree, Kind, Type, TypeTree};
use rustc_ast::node_id::NodeMap;
use rustc_ast::{self as ast};
pub use rustc_ast_ir::{Movability, Mutability, try_visit};
Expand Down Expand Up @@ -67,7 +66,7 @@ pub use rustc_type_ir::solve::{CandidatePreferenceMode, SizedTraitKind, VisibleF
pub use rustc_type_ir::*;
#[allow(hidden_glob_reexports, unused_imports)]
use rustc_type_ir::{InferCtxtLike, Interner};
use tracing::{debug, instrument, trace};
use tracing::{debug, instrument};
pub use vtable::*;

pub use self::closure::{
Expand Down Expand Up @@ -143,6 +142,7 @@ pub mod print;
pub mod relate;
pub mod significant_drop_order;
pub mod trait_def;
pub mod typetree;
pub mod util;
pub mod vtable;

Expand Down Expand Up @@ -2387,228 +2387,3 @@ pub struct DestructuredAdtConst<'tcx> {
pub variant: VariantIdx,
pub fields: &'tcx [ty::Const<'tcx>],
}

/// Generate TypeTree information for autodiff.
/// This function creates TypeTree metadata that describes the memory layout
/// of function parameters and return types for Enzyme autodiff.
pub fn fnc_typetrees<'tcx>(tcx: TyCtxt<'tcx>, fn_ty: Ty<'tcx>) -> FncTree {
// Check if TypeTrees are disabled via NoTT flag
if tcx.sess.opts.unstable_opts.autodiff.contains(&rustc_session::config::AutoDiff::NoTT) {
return FncTree { args: vec![], ret: TypeTree::new() };
}

// Check if this is actually a function type
if !fn_ty.is_fn() {
return FncTree { args: vec![], ret: TypeTree::new() };
}

// Get the function signature
let fn_sig = fn_ty.fn_sig(tcx);
let sig = tcx.instantiate_bound_regions_with_erased(fn_sig);

// Create TypeTrees for each input parameter
let mut args = vec![];
for ty in sig.inputs().iter() {
let type_tree = typetree_from_ty(tcx, *ty);
args.push(type_tree);
}

// Create TypeTree for return type
let ret = typetree_from_ty(tcx, sig.output());

FncTree { args, ret }
}

/// Generate TypeTree for a specific type.
/// This function analyzes a Rust type and creates appropriate TypeTree metadata.
pub fn typetree_from_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> TypeTree {
let mut visited = Vec::new();
typetree_from_ty_inner(tcx, ty, 0, &mut visited)
}

/// Maximum recursion depth for TypeTree generation to prevent stack overflow
/// from pathological deeply nested types. Combined with cycle detection.
const MAX_TYPETREE_DEPTH: usize = 6;

/// Internal recursive function for TypeTree generation with cycle detection and depth limiting.
fn typetree_from_ty_inner<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
depth: usize,
visited: &mut Vec<Ty<'tcx>>,
) -> TypeTree {
if depth >= MAX_TYPETREE_DEPTH {
trace!("typetree depth limit {} reached for type: {}", MAX_TYPETREE_DEPTH, ty);
return TypeTree::new();
}

if visited.contains(&ty) {
return TypeTree::new();
}

visited.push(ty);
let result = typetree_from_ty_impl(tcx, ty, depth, visited);
visited.pop();
result
}

/// Implementation of TypeTree generation logic.
fn typetree_from_ty_impl<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
depth: usize,
visited: &mut Vec<Ty<'tcx>>,
) -> TypeTree {
typetree_from_ty_impl_inner(tcx, ty, depth, visited, false)
}

/// Internal implementation with context about whether this is for a reference target.
fn typetree_from_ty_impl_inner<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
depth: usize,
visited: &mut Vec<Ty<'tcx>>,
is_reference_target: bool,
) -> TypeTree {
if ty.is_scalar() {
let (kind, size) = if ty.is_integral() || ty.is_char() || ty.is_bool() {
(Kind::Integer, ty.primitive_size(tcx).bytes_usize())
} else if ty.is_floating_point() {
match ty {
x if x == tcx.types.f16 => (Kind::Half, 2),
x if x == tcx.types.f32 => (Kind::Float, 4),
x if x == tcx.types.f64 => (Kind::Double, 8),
x if x == tcx.types.f128 => (Kind::F128, 16),
_ => (Kind::Integer, 0),
}
} else {
(Kind::Integer, 0)
};

// Use offset 0 for scalars that are direct targets of references (like &f64)
// Use offset -1 for scalars used directly (like function return types)
let offset = if is_reference_target && !ty.is_array() { 0 } else { -1 };
return TypeTree(vec![Type { offset, size, kind, child: TypeTree::new() }]);
}

if ty.is_ref() || ty.is_raw_ptr() || ty.is_box() {
let Some(inner_ty) = ty.builtin_deref(true) else {
return TypeTree::new();
};

let child = typetree_from_ty_impl_inner(tcx, inner_ty, depth + 1, visited, true);
return TypeTree(vec![Type {
offset: -1,
size: tcx.data_layout.pointer_size().bytes_usize(),
kind: Kind::Pointer,
child,
}]);
}

if ty.is_array() {
if let ty::Array(element_ty, len_const) = ty.kind() {
let len = len_const.try_to_target_usize(tcx).unwrap_or(0);
if len == 0 {
return TypeTree::new();
}
let element_tree =
typetree_from_ty_impl_inner(tcx, *element_ty, depth + 1, visited, false);
let mut types = Vec::new();
for elem_type in &element_tree.0 {
types.push(Type {
offset: -1,
size: elem_type.size,
kind: elem_type.kind,
child: elem_type.child.clone(),
});
}

return TypeTree(types);
}
}

if ty.is_slice() {
if let ty::Slice(element_ty) = ty.kind() {
let element_tree =
typetree_from_ty_impl_inner(tcx, *element_ty, depth + 1, visited, false);
return element_tree;
}
}

if let ty::Tuple(tuple_types) = ty.kind() {
if tuple_types.is_empty() {
return TypeTree::new();
}

let mut types = Vec::new();
let mut current_offset = 0;

for tuple_ty in tuple_types.iter() {
let element_tree =
typetree_from_ty_impl_inner(tcx, tuple_ty, depth + 1, visited, false);

let element_layout = tcx
.layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(tuple_ty))
.ok()
.map(|layout| layout.size.bytes_usize())
.unwrap_or(0);

for elem_type in &element_tree.0 {
types.push(Type {
offset: if elem_type.offset == -1 {
current_offset as isize
} else {
current_offset as isize + elem_type.offset
},
size: elem_type.size,
kind: elem_type.kind,
child: elem_type.child.clone(),
});
}

current_offset += element_layout;
}

return TypeTree(types);
}

if let ty::Adt(adt_def, args) = ty.kind() {
if adt_def.is_struct() {
let struct_layout =
tcx.layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(ty));
if let Ok(layout) = struct_layout {
let mut types = Vec::new();

for (field_idx, field_def) in adt_def.all_fields().enumerate() {
let field_ty = field_def.ty(tcx, args);
let field_tree = typetree_from_ty_impl_inner(
tcx,
field_ty.skip_norm_wip(),
depth + 1,
visited,
false,
);

let field_offset = layout.fields.offset(field_idx).bytes_usize();

for elem_type in &field_tree.0 {
types.push(Type {
offset: if elem_type.offset == -1 {
field_offset as isize
} else {
field_offset as isize + elem_type.offset
},
size: elem_type.size,
kind: elem_type.kind,
child: elem_type.child.clone(),
});
}
}

return TypeTree(types);
}
}
}

TypeTree::new()
}
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