diff --git a/mlir/include/mlir/Dialect/GPU/GPUOps.td b/mlir/include/mlir/Dialect/GPU/GPUOps.td
--- a/mlir/include/mlir/Dialect/GPU/GPUOps.td
+++ b/mlir/include/mlir/Dialect/GPU/GPUOps.td
@@ -834,6 +834,8 @@
     custom<AsyncDependencies>(type($asyncToken), $asyncDependencies) ` `
     `(` $dynamicSizes `)` (`` `[` $symbolOperands^ `]`)? attr-dict `:` type($memref)
   }];
+
+  let hasCanonicalizer = 1;
 }
 
 def GPU_DeallocOp : GPU_Op<"dealloc", [GPU_AsyncOpInterface]> {
@@ -1040,7 +1042,7 @@
     the same value.
 
     This op is meant to be used along with `gpu.subgroup_mma_compute`.
-    
+
     Example:
 
     ```mlir
diff --git a/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp b/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
--- a/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
+++ b/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
@@ -1089,6 +1089,44 @@
   return foldMemRefCast(*this);
 }
 
+//===----------------------------------------------------------------------===//
+// GPU_AllocOp
+//===----------------------------------------------------------------------===//
+namespace {
+
+/// Folding of memref.dim(gpu.alloca(%size), %idx) -> %size similar to
+/// `memref::AllocOp`.
+struct SimplifyDimOfAllocOp : public OpRewritePattern<memref::DimOp> {
+  using OpRewritePattern<memref::DimOp>::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(memref::DimOp dimOp,
+                                PatternRewriter &rewriter) const override {
+    auto index = dimOp.index().getDefiningOp<ConstantIndexOp>();
+    if (!index)
+      return failure();
+
+    auto memrefType = dimOp.source().getType().dyn_cast<MemRefType>();
+    if (!memrefType)
+      return failure();
+
+    auto alloc = dimOp.source().getDefiningOp<AllocOp>();
+    if (!alloc)
+      return failure();
+
+    Value substituteOp = *(alloc.dynamicSizes().begin() +
+                          memrefType.getDynamicDimIndex(index.getValue()));
+    rewriter.replaceOp(dimOp, substituteOp);
+    return success();
+  }
+};
+
+} // end anonymous namespace.
+
+void AllocOp::getCanonicalizationPatterns(RewritePatternSet &results,
+                                          MLIRContext *context) {
+  results.add<SimplifyDimOfAllocOp>(context);
+}
+
 #include "mlir/Dialect/GPU/GPUOpInterfaces.cpp.inc"
 
 #define GET_OP_CLASSES
diff --git a/mlir/test/Dialect/GPU/canonicalize.mlir b/mlir/test/Dialect/GPU/canonicalize.mlir
--- a/mlir/test/Dialect/GPU/canonicalize.mlir
+++ b/mlir/test/Dialect/GPU/canonicalize.mlir
@@ -9,3 +9,16 @@
   gpu.memcpy %0,%1 : memref<?xf32>, memref<?xf32>
   return
 }
+
+// -----
+
+// Test case: Folding of memref.dim(gpu.alloca(%size), %idx) -> %size
+// CHECK-LABEL: func @gpu_dim_of_alloc(
+//  CHECK-SAME:     %[[SIZE:[0-9a-z]+]]: index
+//  CHECK-NEXT:   return %[[SIZE]] : index
+func @gpu_dim_of_alloc(%size: index) -> index {
+  %0 = gpu.alloc(%size) : memref<?xindex>
+  %c0 = constant 0 : index
+  %1 = memref.dim %0, %c0 : memref<?xindex>
+  return %1 : index
+}