Fix non-zero extent of access_ptr out of range (#1937) (#1939)

src/lang/buffer.cc

@@ -357,9 +357,9 @@ Expr Buffer::access_ptr(int access_mask, Type ptr_type, int content_lanes, Expr
   } else if (self->strides.size() == self->shape.size()) {
     int highest_dim = 0;
     extent = arith::ComputeExpr<ir::Mul>(
-        self->strides[highest_dim], self->shape[highest_dim]);
+        self->strides[highest_dim], self->shape[highest_dim]) - offset;
   } else {
-    extent = arith::ComputeReduce<ir::Mul>(self->shape, Expr());
+    extent = arith::ComputeReduce<ir::Mul>(self->shape, Expr()) - offset;
   }
   Expr elem_offset = self->elem_offset + offset;
   if (content_lanes > 1) {

tests/python/unittest/test_lang_buffer.py

@@ -41,6 +41,18 @@ def test_buffer_access_ptr_offset():
     assert tvm.ir_pass.Equal(offset, tvm.call_extern('int32', "test_call", 200 + v))
     assert aptr.args[4].value == Buffer.READ | Buffer.WRITE
 
+def test_buffer_access_ptr_extent():
+    m = tvm.var('m')
+    n = tvm.var('n')
+    Ab = tvm.decl_buffer((m, n), tvm.float32)
+    aptr = Ab.access_ptr("rw")
+    assert tvm.ir_pass.Equal(aptr.args[3], m * n)
+    aptr = Ab.access_ptr("rw", offset=100)
+    assert tvm.ir_pass.Equal(aptr.args[3], m * n - 100)
+    Ab = tvm.decl_buffer((m, n), tvm.float32, strides=[n + 1 , 1])
+    aptr = Ab.access_ptr("rw", offset=100)
+    assert tvm.ir_pass.Equal(aptr.args[3], Ab.strides[0] * m - 100)
+
 def test_buffer_vload():
     m = tvm.var('m')
     n = tvm.var('n')
@@ -84,5 +96,6 @@ if __name__ == "__main__":
     test_buffer()
     test_buffer_access_ptr()
     test_buffer_access_ptr_offset()
+    test_buffer_access_ptr_extent()
     test_buffer_vload()
     test_buffer_index_merge_mult_mod()