Index type is an integer type of target-specific bitwidth present in many MLIR
operations (loops, memory accesses). Converting values of this type to
fixed-size integers has always been problematic. Introduce a data layout entry
to specify the bitwidth of `index` in a given layout scope, defaulting to 64
bits, which is a commonly used assumption, e.g., in constants.
Port builtin-to-LLVM type conversion to use this data layout entry when
converting `index` type and untie it from pointer size. This is particularly
relevant for GPU targets. Keep a possibility to forcibly override the index
type in lowerings.
Depends On D98525
Reviewed By: herhut
Differential Revision: https://reviews.llvm.org/D98937
This is useful for bit-packing types such as vectors and tuples as well as for
exotic architectures that have non-8-bit bytes.
Depends On D98500
Reviewed By: rriddle
Differential Revision: https://reviews.llvm.org/D98524
ModuleOp is a natural place to provide scoped data layout information. However,
it is undesirable for ModuleOp to implement the entirety of
DataLayoutOpInterface because that would require either pushing the interface
inside the IR library instead of a separate library, or putting the default
implementation of the interface as inline functions in headers leading to
binary bloat. Instead, ModuleOp accepts an arbitrary data layout spec attribute
and has a dedicated hook to extract it, and DataLayout is modified to know
about ModuleOp particularities.
Reviewed By: herhut, nicolasvasilache
Differential Revision: https://reviews.llvm.org/D98500
Data layout information allows to answer questions about the size and alignment
properties of a type. It enables, among others, the generation of various
linear memory addressing schemes for containers of abstract types and deeper
reasoning about vectors. This introduces the subsystem for modeling data
layouts in MLIR.
The data layout subsystem is designed to scale to MLIR's open type and
operation system. At the top level, it consists of attribute interfaces that
can be implemented by concrete data layout specifications; type interfaces that
should be implemented by types subject to data layout; operation interfaces
that must be implemented by operations that can serve as data layout scopes
(e.g., modules); and dialect interfaces for data layout properties unrelated to
specific types. Built-in types are handled specially to decrease the overall
query cost.
A concrete default implementation of these interfaces is provided in the new
Target dialect. Defaults for built-in types that match the current behavior are
also provided.
Reviewed By: rriddle
Differential Revision: https://reviews.llvm.org/D97067
Tres Popp