From 3773404551e2487e1b6276ad16997f367eb126f8 Mon Sep 17 00:00:00 2001
From: Tianqi Chen <tqchen@users.noreply.github.com>
Date: Wed, 24 Jan 2018 13:59:30 -0800
Subject: [PATCH] [CODE COMMENT] Comment BindBufferScope (#815)
---
src/pass/storage_flatten.cc | 35 ++++++++++++++++++++++++++++++++++-
1 file changed, 34 insertions(+), 1 deletion(-)
diff --git a/src/pass/storage_flatten.cc b/src/pass/storage_flatten.cc
index 45ad081f8..bc380d473 100644
--- a/src/pass/storage_flatten.cc
+++ b/src/pass/storage_flatten.cc
@@ -296,7 +296,40 @@ class StorageFlattener : public IRMutator {
}
private:
- // Start bind
+ // The specific tensor data layout is not determined before
+ // StorageFlatten pass. We use buffer_bind_scope
+ // to specify before hand we want to bind a subregion
+ // of tensor to a symbolic buffer, which get used in extern.
+ //
+ // Example:
+ //
+ // realize A in range [i*4, extent=10) {
+ // bind Ab to A in [i*4+1, extent=4) {
+ // call_func(Ab.ptr, Ab.shape[0])
+ // }
+ // }
+ //
+ // After StorageFlatten
+ //
+ // alloc A[10]
+ // call(A + 1, 4)
+ //
+ // Buffer is a protocol to declare specific
+ // data layout and shape we expect.
+ // So this function need to check:
+ // - If the bind range is within the realize range
+ // - If we can match the requirement of buffer
+ // - Remap variables such as Ab.ptr to the actual value.
+ //
+ // Here are a few possible failure cases:
+ // - Buffer is declared to have constant shape,
+ // but we try to bind it to a different one.
+ // - Buffer is declared to be compact(no strides)
+ // but this binded region is a subregion of
+ // a matrix(tensor), which means it requires strides.
+ //
+ // We do support a few relaxed case, such as bindingx
+ // region with shape [1, 1, n, m] to buffer with shape [n, m]
Stmt HandleBufferBindScope(const AttrStmt* op) {
Array<NodeRef> arr(op->node.node_);
CHECK_EQ(arr.size(), 2U);
--
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