[Mlir-commits] [mlir] [tosa] : Enhance tosa.slice folding for dynamic dims. (PR #184045)

[Luke Hutton]

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@@ -1771,6 +1771,56 @@ OpFoldResult SliceOp::fold(FoldAdaptor adaptor) {
   if (inputTy == outputTy && inputTy.hasStaticShape())
     return getInput1();
 
+  // Check if this is a no-op slice (starts at 0 and size matches input)
+
+  DenseElementsAttr startElems;
+  if (!matchPattern(getStart(), m_Constant(&startElems)))
+    return {};
+
+  // Check if all start values are zero
+  bool startIsZeros =
+      llvm::all_of(startElems.getValues<APInt>(),
+                   [](const APInt &val) { return val.isZero(); });
+
+  if (startIsZeros) {
+
+    // Check if size matches input shape
+    DenseElementsAttr sizeElems;
+    if (!matchPattern(getSize(), m_Constant(&sizeElems)))
+      return {};
+
+    auto inputShape = inputTy.getShape();
+    auto sizeValues = sizeElems.getValues<APInt>();
+
+    if (sizeValues.size() != inputShape.size())
+      return {};
+
+    bool sizeMatchesInput = true;
+    for (const auto &[i, sizeVal] : llvm::enumerate(sizeValues)) {
+      int64_t size = sizeVal.getSExtValue();
+
+      if (inputTy.isDynamicDim(i)) {
+        // For dynamic dimensions, check for -1 indicating full dimension is
+        // sliced
+        if (size != -1) {
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lhutton1 wrote:

nit: could we update use of -1 to use the new `kInferableDimSize` constant?

https://github.com/llvm/llvm-project/pull/184045