fixup! [mlir][vector] Clarify the semantics of BroadcastOp

Address comments from Hugo - thank you!

Author: banach-space

mlir/include/mlir/Dialect/Vector/IR/VectorOps.td

@@ -367,7 +367,7 @@ def Vector_BroadcastOp :
                                s_1     x .. x s_j x .. x s_k
                <duplication>         <potential stretch>
        ```
-    * a scalable unit dimeension, `[1]`, must match exactly.
+    * a scalable unit dimension, `[1]`, must match exactly.
 
     The source operand is duplicated over all the missing leading dimensions
     and stretched over the trailing dimensions where the source has a non-equal

mlir/lib/Dialect/Vector/IR/VectorOps.cpp

@@ -2403,7 +2403,7 @@ BroadcastableToResult mlir::vector::isBroadcastableTo(
     bool srcDimScalableFlag = srcVectorType.getScalableDims()[r];
     bool dstDimScalableFlag = dstVectorType.getScalableDims()[lead + r];
     if ((srcDim == 1 && srcDimScalableFlag && dstDim != 1) ||
-        (srcDimScalableFlag && !dstDimScalableFlag))
+        (srcDimScalableFlag != dstDimScalableFlag))
       mismatch = true;
 
     if (mismatch) {

mlir/test/Dialect/Vector/invalid.mlir

@@ -42,6 +42,13 @@ func.func @broadcast_scalable_unit_dim(%arg0: vector<[1]xf32>) {
 
 // -----
 
+func.func @broadcast_fixed_to_scalable(%arg0: vector<2xf32>) {
+  // expected-error@+1 {{'vector.broadcast' op dimension mismatch (2 vs. [2])}}
+  %0 = vector.broadcast %arg0 : vector<2xf32> to vector<[2]xf32>
+}
+
+// -----
+
 func.func @broadcast_scalable_to_fixed(%arg0: vector<[1]xf32>) {
   // expected-error@+1 {{'vector.broadcast' op dimension mismatch ([1] vs. 1)}}
   %0 = vector.broadcast %arg0 : vector<[1]xf32> to vector<4x1xf32>