## Summary
- Make `PrimExpr` a typed C++ view over `Expr` values whose
`ExprNode::ty` is `PrimType`, instead of using a separate runtime node
class as the proof of primitive-ness.
- Use the shared `ir::Call` node for Relax, TIRX, and primitive-valued
calls, while keeping primitive-only APIs explicit at their semantic
boundaries.
- Keep Python on the general `Expr` surface for primitive-typed values
so `isinstance` behavior does not imply a nominal primitive-expression
subclass.
## Design Rationale
The main advantage of this change is that common expression nodes such
as `Call` can be unified without specializing each one to `PrimType`. A
single `ir::Call` can represent a Relax tensor call, a Relax scalar
call, or a primitive-valued intrinsic call; the result type stored in
`ExprNode::ty` determines whether that particular value can be viewed as
`PrimExpr`.
This keeps the IR node hierarchy focused on expression structure rather
than result-type categories. Nodes that are intrinsically primitive,
such as integer and floating-point literals or TIRX primitive operators,
still have strongly typed C++ APIs and data structures. General nodes
whose result type may vary, such as `Call`, remain general `Expr` nodes
and are narrowed to `PrimExpr` only where primitive-only semantics are
required.
The PR also keeps the compatibility surface practical: C++
primitive-only APIs continue to accept `PrimExpr`, Python exposes a
compatibility predicate for checking the primitive typed category, and
visitors/printers use one natural `Call` path rather than duplicating
Relax and primitive call handling. Missing expression types are
represented explicitly with `Type::Missing()` so constructors can leave
type inference to later analysis without relying on nullable `Type`
values.
In the past we have been using `DataType` in PrimExpr.dtype field to
check type information for PrimExpr while still having BaseExpr.ty for
richer type information. DataType is also used both in runtime and
compiler. This PR streamlines the boundary:
- PrimExpr.ty now carries PrimType that replaces original use of
`DataType`
- Runtime use will now favor DLPack DLDataType, removing one layer of
indirection.
- Constants attributes where values are usually runtime values, will use
`DLDataType`
- DataType will be phased out after this PR
We also brings up helper functions in PrimType, but also limits them to
a more concise set so the functions do not grow with the data type codes
in DLPack.
This is a major refactor that changes the IR primitive. It helps to
bring possible future benefits:
- Unified type mechanism through Expr.ty
- Possibility of carry future Type nodes
Migration Guide:
- Use `PrimType` when code reasons about compiler expression types,
tensor element compiler types, or constructs a `PrimExpr`/compiler type.
- Use existing source types such as `expr.ty()`, `ExprOp.expr_ty()`, or
TE tensor element `dtype` where possible instead of rebuilding a type
from dtype text.
- Use raw `DLDataType` for runtime constants, ABI paths, dtype-valued
attrs, and storage/runtime helper logic.
- Prefer direct `PrimType` equality, `MatchesCode(...)`,
`MatchesElementType(...)`, and `WithCode(...)` over local wrappers or
string dtype checks.
Performance:
Using Object type instead of DLDataType would indeed bring some
performance impact to the IR. We have done the following performance
optimizations:
- Make sure most of the outputs reuse one of the PrimType from inputs
- Cache a thread local PrimType based on input so we don't repeatly
realloc
We did benchmarks show that rewrite simplify operation stays within
+-10% overhead of original one. Which merits the refactor given the
benefit the unfication brings
## Summary
Restructure TVMScript to be dialect-agnostic at the script-core layer
while letting each extension dialect (TIRX, Relax) own its own
per-dialect script subtree. IR is below script in the dependency
stack and is NOT a peer dialect — its script handlers stay in the
shared core.
This PR folds together two coupled refactors that were initially
opened as separate PRs (#19478 and the original #19479); they
share rename / relocation surface so they ship as one cohesive
change.
## What this PR does
### Per-dialect script subtree (originally #19479)
- Moves per-dialect printer + builder from
`src/script/{printer,ir_builder}/{tirx,relax}/` to
`src/{tirx,relax}/script/{printer,builder}/`.
- Tightens `src/script/*.cc` CMake glob to the dialect-free core.
- Refactors `IRBuilder::DeclFunction` to dispatch via FFI registry
(`script.ir_builder.decl_function.<type-key>`); removes
cross-dialect includes from the shared core.
- Adds `tvm.script.register_dialect` API + `__getattr__` + a
`sys.meta_path` finder for Python-side dialect discovery.
In-tree dialects (tirx, relax) registered centrally in
`python/tvm/__init__.py`.
- Drops the obsolete static re-export shims at
`python/tvm/script/{parser,ir_builder}/{tirx,relax}/`.
### Dialect-agnostic printer config (originally #19478)
- Relocates `include/tvm/ir/script_printer.h` →
`include/tvm/script/printer/config.h` next to the rest of the
printer's public surface. The header is not IR-specific.
- Renames `TVM_SCRIPT_REPR` → `TVM_REGISTER_SCRIPT_AS_REPR` for
clarity (the macro registers Script as the kRepr callback +
per-type vtable dispatch). Aligns with the `TVM_REGISTER_*`
family.
- Drops dialect-hardcoded `PrinterConfig` fields (`tir_prefix`,
`relax_prefix`, `show_all_struct_info`, `buffer_dtype`) in favor
of a generic `ffi::Map<String, Any> extra_config` keyed by
`"<dialect>.<knob>"`. Each call site reads via the templated
accessor `config->GetExtraConfig<T>("...", default)`.
- Promotes `std::string` config fields to `ffi::String`.
After this lands, the script-printer core knows nothing specific
about any dialect — new dialects plug in via the registry pattern
with zero core edits. Public Python API surface unchanged.
Tianqi Chen