[Mlir-commits] [mlir] [mlir][vector] Clarify the semantics of BroadcastOp (PR #101928)

[Andrzej Warzyński]

================
@@ -2391,12 +2391,28 @@ mlir::vector::isBroadcastableTo(Type srcType, VectorType dstVectorType,
   // (all leading dimensions are simply duplicated).
   int64_t lead = dstRank - srcRank;
   for (int64_t r = 0; r < srcRank; ++r) {
+    bool mismatch = false;
+
+    // Check fixed-width dims
     int64_t srcDim = srcVectorType.getDimSize(r);
     int64_t dstDim = dstVectorType.getDimSize(lead + r);
-    if (srcDim != 1 && srcDim != dstDim) {
+    if ((srcDim != 1 && srcDim != dstDim))
+      mismatch = true;
+
+    // Check scalable flags
+    bool srcDimScalableFlag = srcVectorType.getScalableDims()[r];
+    bool dstDimScalableFlag = dstVectorType.getScalableDims()[lead + r];
+    if ((srcDim == 1 && srcDimScalableFlag && dstDim != 1) ||
+        (srcDimScalableFlag && !dstDimScalableFlag))
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banach-space wrote:

If you have e.g. `[2]` and `[4]` (i.e. `vscale * 2` and `vscale * 4`), then that's already "rejected" as "mismatching dims":
* https://github.com/llvm/llvm-project/blob/0dcada94bb1ae79f0edd91013038098c62a96b3b/mlir/lib/Dialect/Vector/IR/VectorOps.cpp#L2396

Is that the case you had in mind?

https://github.com/llvm/llvm-project/pull/101928