Amend RFC0070 with DeclBuffer TVMScript syntax updates

rfcs/0070-introducing-decl-buffer.md

@@ -87,7 +87,7 @@ Allocate {
 This can also be represented in TVMScript:
 ```
 A_data = T.allocate(shape=..., dtype=...)
-A = T.decl_buffer(data=A_data)
+A = T.decl_buffer(shape=..., dtype=..., data=A_data)
 ```
 
 ## Declaration of buffer alias
@@ -132,8 +132,8 @@ After flattening:
 ```
 @T.prim_func
 def elemwise(A: T.Buffer[(16, 16), "float32"], C: T.Buffer[(16, 16), "float32"]):
-    A_flattened = T.decl_buffer(A.data, (256,), "float32")
-    C_flattened = T.decl_buffer(C.data, (256,), "float32")
+    A_flattened = T.decl_buffer(shape=(256,), dtype="float32", data=A.data)
+    C_flattened = T.decl_buffer(shape=(256,), dtype="float32", data=C.data)
     for i, j in T.grid(16, 16):
         C_flattened[i * 16 + j] = A[i * 16 + j]
 ```
@@ -146,9 +146,36 @@ Specifically, the updated flow of buffer flattening using `DeclBuffer` will be:
 with flattened indices.
 
 ## TVM script updates
+* New statement `T.decl_buffer` will be introduced. It has the same interface as `T.buffer_decl`.
+```python
+def decl_buffer(
+    shape: Sequence[Union[PrimExpr, int]],
+    dtype: str = "float32",
+    data: Var = None,
+    strides: Optional[Sequence[int]] = None,
+    elem_offset: Optional[int] = None,
+    scope: str = "global",
+    align: int = -1,
+    offset_factor: int = 0,
+    buffer_type: str = "default",
+    axis_separators: Optional[List[int]] = None,
+) -> Buffer: ...
+```
+It will be parsed to `DeclBuffer` node.
+
 * `T.allocate` will return data variable instead of a buffer. If the subsequent program need to access
 the data variable as a buffer, it should use `T.decl_buffer` to declare the buffer.
-* `T.buffer_decl` will be renamed to `T.decl_buffer`.
+* As a syntax sugar to avoid writing both `T.allocate` and `T.decl_buffer` at the same time,
+when the `data` parameter is not specified for `T.decl_buffer`, the buffer data will be
+allocated implicitly. This means the following code snippets are equivalent:
+```
+A_data = T.allocate(shape=[16], dtype="float32")
+A = T.decl_buffer(shape=[16], dtype="float32", data=A_data)
+```
+```
+A = T.decl_buffer(shape=[16], dtype="float32")
+```
+* `T.buffer_decl` will be deprecated in favor of the explicit `T.decl_buffer`.
 
 ## TIR validation
 With `DeclBuffer` introduced, we can implement utilities for TIR validation. It will enforce that: