[Mlir-commits] [mlir] [mlir][ArmSVE] Add convert_to/from_svbool ops (PR #68586)

[Cullen Rhodes]

================
@@ -236,6 +243,81 @@ def UmmlaOp : ArmSVE_Op<"ummla",
     "$acc `,` $src1 `,` $src2 attr-dict `:` type($src1) `to` type($dst)";
 }
 
+class SvboolTypeConstraint<string lhsArg, string rhsArg> : TypesMatchWith<
+      "expected corresponding svbool type widened to [16]xi1",
+      lhsArg, rhsArg,
+      "VectorType(VectorType::Builder(::llvm::cast<VectorType>($_self)).setDim(::llvm::cast<VectorType>($_self).getRank() - 1, 16))">;
+
+def ConvertFromSvboolOp : ArmSVE_Op<"convert_from_svbool",
+                            [Pure, SvboolTypeConstraint<"result", "source">]>
+{
+  let summary = "Convert a svbool type to a SVE predicate type";
+  let description = [{
+    Converts svbool types (`vector<[16]xi1>` or vectors of that type, e.g.
+    `vector<2x3x[16]xi1>`) to SVE predicate types. Note: Only the trailing
+    dimension can be scalable.
+
+    Example 1: Convert a 1-D svbool mask to a SVE predicate.
+    ```mlir
+    %source = vector.load %memref[%c0] : memref<?xi1>, vector<[16]xi1>
+    %result = arm_sve.convert_from_svbool %source : vector<[4]xi1>
+    ```
+
+    Example 2: Convert a 2-D svbool mask to a mask of SVE predicates.
+    ```mlir
+    %source = vector.load %memref[%c0, %c0] : memref<2x?xi1>, vector<2x[16]xi1>
+    %result = arm_sve.convert_from_svbool %source : vector<2x[8]xi1>
+    ```
+
+    ---
+
+    A `svbool` is the smallest SVE predicate type that has a in-memory
+    representation (and maps to a full predicate register). In MLIR `svbool` is
+    represented as `vector<[16]xi1>`. Smaller SVE predicate types
+    (`vector<[1|2|4|8]xi1>`) must be stored as `svbool` then converted back to
+    a predicate after loading.
----------------
c-rhodes wrote:

```suggestion
    (`vector<[1|2|4|8]xi1>`) must be stored as `svbool` then converted back to
    the original predicate type after loading.
```

https://github.com/llvm/llvm-project/pull/68586