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Currently, type casts can only be used to pattern match for intrinsics with a single overloaded return value. For instance: ``` def int_foo : Intrinsic<[llvm_anyint_ty], []>; def : Pat<(i32 (int_foo)), ...>; ``` This patch extends type casts to support matching intrinsics with multiple overloaded return values. As an example, the following defines a pattern that matches only if the overloaded intrinsic call returns an `i16` for the first result and an `i32` for the second result: ``` def int_bar : Intrinsic<[llvm_anyint_ty, llvm_anyint_ty], []>; def : Pat<([i16, i32] (int_bar)), ...>; ```
LLVM TableGen
The purpose of TableGen is to generate complex output files based on information from source files that are significantly easier to code than the output files would be, and also easier to maintain and modify over time.
The information is coded in a declarative style involving classes and records, which are then processed by TableGen.
class Hello <string _msg> {
string msg = !strconcat("Hello ", _msg);
}
def HelloWorld: Hello<"world!"> {}
------------- Classes -----------------
class Hello<string Hello:_msg = ?> {
string msg = !strconcat("Hello ", Hello:_msg);
}
------------- Defs -----------------
def HelloWorld { // Hello
string msg = "Hello world!";
}
Try this example on Compiler Explorer.
The internalized records are passed on to various backends, which extract information from a subset of the records and generate one or more output files.
These output files are typically .inc files for C++, but may be any type of file that the backend developer needs.
Resources for learning the language:
- TableGen Overview
- Programmer's reference guide
- Tutorial
- Tools for Learning LLVM TableGen
- Lessons in TableGen (video), slides
- Improving Your TableGen Descriptions (video), slides
Writing TableGen backends:
- TableGen Backend Developer's Guide
- How to write a TableGen backend (video), slides, also available as a notebook.
TableGen in MLIR:
Useful tools: