[mlir][CPURunner] Avoid a crash in memrefCopy when called with empty shapes.

Differential Revision: https://reviews.llvm.org/D107346

Author: akuegel

mlir/lib/ExecutionEngine/CRunnerUtils.cpp

@@ -47,6 +47,11 @@ memrefCopy(int64_t elemSize, UnrankedMemRefType<char> *srcArg,
   DynamicMemRefType<char> dst(*dstArg);
 
   int64_t rank = src.rank;
+  // Handle empty shapes -> nothing to copy.
+  for (int rankp = 0; rankp < rank; ++rankp)
+    if (src.sizes[rankp] == 0)
+      return;
+
   char *srcPtr = src.data + src.offset * elemSize;
   char *dstPtr = dst.data + dst.offset * elemSize;
 
@@ -83,7 +88,7 @@ memrefCopy(int64_t elemSize, UnrankedMemRefType<char> *srcArg,
       if (axis == 0)
         return;
       // Else, reset to 0 and undo the advancement of the linear index that
-      // this axis had. The continue with the axis one outer.
+      // this axis had. Then continue with the axis one outer.
       indices[axis] = 0;
       readIndex -= src.sizes[axis] * srcStrides[axis];
       writeIndex -= dst.sizes[axis] * dstStrides[axis];

mlir/test/mlir-cpu-runner/copy.mlir

@@ -45,5 +45,10 @@ func @main() -> () {
   // CHECK-NEXT: [1,   4]
   // CHECK-NEXT: [2,   5]
 
+  %input_empty = memref.alloc() : memref<3x0x1xf32>
+  %copy_empty = memref.alloc() : memref<3x0x1xf32>
+  // Copying an empty shape should do nothing (and should not crash).
+  memref.copy %input_empty, %copy_empty : memref<3x0x1xf32> to memref<3x0x1xf32>
+
   return
 }