[all-commits] [llvm/llvm-project] 17de46: [mlir][llvm] Add llvm.target_features features att...

[Benjamin Maxwell via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 17de468df1af6479f31bb8c02973e01702f7b240
      https://github.com/llvm/llvm-project/commit/17de468df1af6479f31bb8c02973e01702f7b240
  Author: Benjamin Maxwell <benjamin.maxwell at arm.com>
  Date:   2023-12-05 (Tue, 05 Dec 2023)

  Changed paths:
    M mlir/include/mlir/Dialect/LLVMIR/LLVMAttrDefs.td
    M mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
    M mlir/lib/Dialect/LLVMIR/IR/LLVMAttrs.cpp
    M mlir/lib/Target/LLVMIR/ModuleImport.cpp
    M mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
    A mlir/test/Target/LLVMIR/Import/target-features.ll
    M mlir/test/Target/LLVMIR/llvmir-invalid.mlir
    A mlir/test/Target/LLVMIR/target-features.mlir

  Log Message:
  -----------
  [mlir][llvm] Add llvm.target_features features attribute (#71510)

This patch adds a target_features (TargetFeaturesAttr) to the LLVM
dialect to allow setting and querying the features in use on a function.

The motivation for this comes from the Arm SME dialect where we would
like a convenient way to check what variants of an operation are
available based on the CPU features.

Intended usage:

The target_features attribute is populated manually or by a pass:

```mlir
func.func @example() attributes {
   target_features = #llvm.target_features<["+sme", "+sve", "+sme-f64f64"]>
} {
 // ...
}
```

Then within a later rewrite the attribute can be checked, and used to
make lowering decisions.

```c++
// Finds the "target_features" attribute on the parent
// FunctionOpInterface.
auto targetFeatures = LLVM::TargetFeaturesAttr::featuresAt(op);

// Check a feature.
// Returns false if targetFeatures is null or the feature is not in
// the list.
if (!targetFeatures.contains("+sme-f64f64"))
    return failure();
```

For now, this is rather simple just checks if the exact feature is in
the list, though it could be possible to extend with implied features
using information from LLVM.