From 35839aee246c07b52fc73f49f3a055e27c95f0b8 Mon Sep 17 00:00:00 2001
From: Chen Weihang <chenweihang@baidu.com>
Date: Wed, 10 Aug 2022 04:03:50 -0500
Subject: [PATCH] polish backend and layout details (#45029)

---
 paddle/phi/common/backend.h |  3 +--
 paddle/phi/common/layout.h  | 19 ++++++++++++++++++-
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/paddle/phi/common/backend.h b/paddle/phi/common/backend.h
index c6d49bd5b97..bfdc3814823 100644
--- a/paddle/phi/common/backend.h
+++ b/paddle/phi/common/backend.h
@@ -48,6 +48,7 @@ enum class Backend : uint8_t {
   XPU,  // XPU currently does not exist at the same time as CUDA
   NPU,  // NPU currently does not exist at the same time as CUDA
   MLU,  // MLU currently does not exist at the same time as CUDA
+  IPU,
 
   // the third library backend
   ONEDNN,
@@ -56,8 +57,6 @@ enum class Backend : uint8_t {
   // paddle kernel primitives backend
   KPS,
 
-  IPU,
-
   // end of backend types
   NUM_BACKENDS,
 
diff --git a/paddle/phi/common/layout.h b/paddle/phi/common/layout.h
index 6b2f657699f..2d74abeb84d 100644
--- a/paddle/phi/common/layout.h
+++ b/paddle/phi/common/layout.h
@@ -18,8 +18,20 @@ limitations under the License. */
 namespace paddle {
 namespace experimental {
 
+// Note: The original design of paddle DataLayout is confusing.
+// It contains two levels of "layout", one is the data layout
+// at the Tensor level, including Dense, Sparse, etc., and the other
+// is the format at the data level, including NHWC, NCHW, etc.,
+// these should belong to the concept of "data format".
+// The concepts of these two levels are mixed into an enumeration class,
+// which leads to some strange execution scheduling logic.
+// It needs to be refactored in the future.
+// In order to maintain compatibility, we still use the design of the
+// original framework here.
+
 // Note: Here the DataLayout is public api for external users, the prefix `k`
 // maybe confuse users, so we use all uppercase names
+
 enum class DataLayout {
   UNDEFINED = 0,
   // TODO(chenweihang): keep ANY for compatibility, remove it later
@@ -32,16 +44,21 @@ enum class DataLayout {
   SPARSE_COO,
   SPARSE_CSR,
   PSTRING_UNION,
+
   NUM_DATA_LAYOUTS,
+
   // See Note [ Why we need ALL in basic kernel key member? ]
   ALL_LAYOUT = UNDEFINED,
+
   // Note: Unify phi DataLayout and fluid::framework::DataLayout,
   // for compatible with fluid DataLayout, here need prefix `k`
+
   // Note: The original `kAnyLayout (enum value 2)` is a strange design.
   // `kAnyLayout` originally cannot represent any kind of Layout,
   // at the same time, it can also represent any Layout.
   // Strictly, it means "default" or "undefined" layout,
-  // and should not be mixed with other meaningful layouts.
+  // and should not be mixed with other meaningful layouts
+
   kAnyLayout = ANY,
   kNHWC = NHWC,
   kNCHW = NCHW,
-- 
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