[Mlir-commits] [mlir] [mlir][tablegen] Correctly set Type constraint description (PR #110939)

[llvmlistbot at llvm.org]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-mlir-core

@llvm/pr-subscribers-mlir

Author: luis (penagos)

<details>
<summary>Changes</summary>

The common tablegen `Type` constraint was not honoring user specified description strings by unconditionally setting `Constraint`'s description to the empty string (this appears to be inadvertent fallout from https://reviews.llvm.org/D94133 in which `typeDescription` was renamed to `description`, shadowing the existing `description` field on `Constraint`).

This has the effect of making select quantized types (among other things) indistinguishable. For example, quantized types in the TFLite dialect are defined as:

```
def QUI8 : QuantizedType<"Uniform", [8], 0>;
def QI8 : QuantizedType<"Uniform", [8], 1>;
```

Where `QuantizedType` is:
```
class QuantizedType<string n, list<int> params, bit signed>
  : Type<And<[CPred<"$_self.isa<mlir::quant::QuantizedType>()">,
              CPred<"$_self.cast<mlir::quant::QuantizedType>()" #
                    ".getStorageTypeIntegralWidth() == " # !head(params)>]>,
    "Q" # !if (signed, "I", "UI") # !head(params) # " type"> {
  string name = n;
  string asTraitArgsStr =
    !interleave(params, ", ") # !if(signed, ", true", ", false");
}
```

Aside from `asTraitArgsStr`, signed/unsigned quantized types are indistinguishable at the parsed TD level, aside from the `description` passed to `Type`. This fix forwards the user provided description to the underlying `Constraint` from which `Type` inherits from.



---
Full diff: https://github.com/llvm/llvm-project/pull/110939.diff


1 Files Affected:

- (modified) mlir/include/mlir/IR/CommonTypeConstraints.td (+1-1) 


``````````diff
diff --git a/mlir/include/mlir/IR/CommonTypeConstraints.td b/mlir/include/mlir/IR/CommonTypeConstraints.td
index 211385245555ad..f5ed8d8a4b0a6b 100644
--- a/mlir/include/mlir/IR/CommonTypeConstraints.td
+++ b/mlir/include/mlir/IR/CommonTypeConstraints.td
@@ -100,7 +100,7 @@ def HasValueSemanticsPred : CPred<"$_self.hasTrait<::mlir::ValueSemantics>()">;
 class Type<Pred condition, string descr = "",
            string cppType = "::mlir::Type"> :
     TypeConstraint<condition, descr, cppType> {
-  string description = "";
+  string description = descr;
   string builderCall = "";
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/110939