diff --git a/mlir/lib/Conversion/ShapeToStandard/ShapeToStandard.cpp b/mlir/lib/Conversion/ShapeToStandard/ShapeToStandard.cpp
--- a/mlir/lib/Conversion/ShapeToStandard/ShapeToStandard.cpp
+++ b/mlir/lib/Conversion/ShapeToStandard/ShapeToStandard.cpp
@@ -38,32 +38,6 @@
   }
 };
 
-class IndexToSizeOpConversion : public OpConversionPattern<IndexToSizeOp> {
-public:
-  using OpConversionPattern<IndexToSizeOp>::OpConversionPattern;
-
-  LogicalResult
-  matchAndRewrite(IndexToSizeOp op, ArrayRef<Value> operands,
-                  ConversionPatternRewriter &rewriter) const override {
-    IndexToSizeOp::Adaptor transformed(operands);
-    rewriter.replaceOp(op.getOperation(), transformed.arg());
-    return success();
-  }
-};
-
-class SizeToIndexOpConversion : public OpConversionPattern<SizeToIndexOp> {
-public:
-  using OpConversionPattern<SizeToIndexOp>::OpConversionPattern;
-
-  LogicalResult
-  matchAndRewrite(SizeToIndexOp op, ArrayRef<Value> operands,
-                  ConversionPatternRewriter &rewriter) const override {
-    SizeToIndexOp::Adaptor transformed(operands);
-    rewriter.replaceOp(op.getOperation(), transformed.arg());
-    return success();
-  }
-};
-
 class ConstSizeOpConverter : public OpConversionPattern<ConstSizeOp> {
 public:
   using OpConversionPattern<ConstSizeOp>::OpConversionPattern;
@@ -132,9 +106,7 @@
   patterns.insert<
       BinaryOpConversion<AddOp, AddIOp>,
       BinaryOpConversion<MulOp, MulIOp>,
-      ConstSizeOpConverter,
-      IndexToSizeOpConversion,
-      SizeToIndexOpConversion>(ctx);
+      ConstSizeOpConverter>(ctx);
   // clang-format on
 }
 
diff --git a/mlir/lib/Conversion/ShapeToStandard/ShapeToStandardPatterns.td b/mlir/lib/Conversion/ShapeToStandard/ShapeToStandardPatterns.td
--- a/mlir/lib/Conversion/ShapeToStandard/ShapeToStandardPatterns.td
+++ b/mlir/lib/Conversion/ShapeToStandard/ShapeToStandardPatterns.td
@@ -10,3 +10,12 @@
     (Shape_ToExtentTensorOp $input),
     (replaceWithValue $input)>;
 
+// Convert `index_to_size` and `size_to_index` to no-ops as sizes will be
+// represented as indices.
+def IndexToSizeOpConversion : Pat<
+    (Shape_IndexToSizeOp $arg),
+    (replaceWithValue $arg)>;
+def SizeToIndexOpConversion : Pat<
+    (Shape_SizeToIndexOp $arg),
+    (replaceWithValue $arg)>;
+