More on source reference (#466)

HalideIR @ cb3c025d

-Subproject commit f3eb854595ff99f4b05a5d8034bcacea30ef045b
+Subproject commit cb3c025d5b91ab994b063a85bc935fc364d8f491

README.md

@@ -33,7 +33,6 @@ Acknowledgement
 ---------------
 We learnt a lot from the following projects when building TVM.
 - [Halide](https://github.com/halide/Halide): TVM uses [HalideIR](https://github.com/dmlc/HalideIR) as data structure for
-  arithematic simplification and low level lowering. HalideIR is derived from Halide.
-  We also learns from Halide when implementing the lowering pipeline in TVM.
+  arithematic simplification and low level lowering. We also learnt and adapted some part of lowering pipeline from Halide.
 - [Loopy](https://github.com/inducer/loopy): use of integer set analysis and its loop transformation primitives.
 - [Theano](https://github.com/Theano/Theano): the design inspiration of symbolic scan operator for recurrence.

src/codegen/llvm/codegen_llvm.cc

@@ -3,6 +3,7 @@
  * \file codegen_llvm.cc
  */
 #ifdef TVM_LLVM_VERSION
+// Part of the code are adapted from Halide's CodeGen_LLVM
 
 #include <tvm/runtime/device_api.h>
 #include <tvm/runtime/c_runtime_api.h>
@@ -492,6 +493,7 @@ llvm::Value* CodeGenLLVM::CreateBufferPtr(
   if (btype != ptype) {
     buffer = builder_->CreatePointerCast(buffer, ptype);
   }
+
   return builder_->CreateInBoundsGEP(buffer, index);
 }
 

src/pass/inject_prefetch.cc

@@ -2,6 +2,7 @@
  *  Copyright (c) 2017 by Contributors
  * \file inject_prefetch.cc
  */
+// Inject prefetch op in HalideIR
 #include <tvm/ir.h>
 #include <tvm/ir_mutator.h>
 #include <tvm/ir_visitor.h>

src/pass/storage_flatten.cc

@@ -2,6 +2,8 @@
  *  Copyright (c) 2016 by Contributors
  * \file storage_flatten.cc
  */
+// Flattens storage from multi-dimensional array to 1D
+// buffer access as in Halide pipeline.
 #include <tvm/ir.h>
 #include <tvm/expr.h>
 #include <tvm/operation.h>

src/pass/unroll_loop.cc

 /*!
  *  Copyright (c) 2017 by Contributors
- *  Loop unrolling.
+ *  Loop unrolling as in Halide pipeline.
  * \file unroll_loop.cc
  */
+// Unrolls the loop as in Halide pipeline.
 #include <tvm/ir.h>
 #include <tvm/ir_pass.h>
 #include <tvm/ir_mutator.h>

src/pass/vectorize_loop.cc

 /*!
  *  Copyright (c) 2017 by Contributors
- *  Vectorize the loop
  * \file vectorize_loop.cc
  */
+// Loop vectorizer as in Halide pipeline.
 #include <tvm/ir.h>
 #include <tvm/ir_pass.h>
 #include <tvm/ir_mutator.h>