[PASS] add a pass for the specific hardware accelarator when it is not binded (#1999)

include/tvm/ir.h

@@ -238,6 +238,11 @@ constexpr const char* pipeline_exec_scope = "pipeline_exec_scope";
 constexpr const char* opengl_stage_scope = "opengl_stage_scope";
 
 /*!
+ * \brief Mark that it is in the device scope.
+ */
+constexpr const char* device_scope = "device_scope";
+
+/*!
  * \brief Check if attr_key is a pragma key extension
  * \param attr_key The attr key to be compared
  * \return true if it is a pragma key

include/tvm/ir_pass.h

@@ -327,6 +327,15 @@ Stmt RewriteUnsafeSelect(Stmt stmt);
 Stmt LowerStorageAccessInfo(Stmt stmt);
 
 /*!
+ * \brief Decorate the stmt with a device scope, this is helpful for 
+ * hardware accelerator without thread blocks.
+ *
+ * \param stmt The stmt to be trasnformed
+ * \return Transformed stmt.
+ */
+Stmt DecorateDeviceScope(Stmt stmt);
+
+/*!
  * \brief Make an user callable API LoweredFunc.
  *
  *  The main task of this function is to create code to :

src/api/api_pass.cc

@@ -154,5 +154,6 @@ REGISTER_PASS1(LowerTVMBuiltin);
 REGISTER_PASS1(CombineContextCall);
 REGISTER_PASS2(VerifyMemory);
 REGISTER_PASS2(VerifyGPUCode);
+REGISTER_PASS1(DecorateDeviceScope);
 }  // namespace ir
 }  // namespace tvm

src/pass/detect_device.cc

+/*!
+ *  Copyright (c) 2018 by Contributors
+ * \file detect_device.cc
+ */
+
+#include <tvm/ir_pass.h>
+#include <tvm/ir_mutator.h>
+#include "../pass/ir_util.h"
+
+namespace tvm {
+namespace ir {
+Stmt DecorateDeviceScope(Stmt stmt) {
+  Stmt body = AttrStmt::make(make_zero(Int(32)),
+                             ir::attr::device_scope,
+                             0,
+                             stmt);
+  return body;
+}
+
+}  // namespace ir
+}  // namespace tvm

src/pass/split_host_device.cc

@@ -153,7 +153,8 @@ class HostDeviceSplitter : public IRMutator {
 
   Stmt Mutate_(const AttrStmt *op, const Stmt& s) final {
     if (op->attr_key == attr::thread_extent ||
-        op->attr_key == attr::pipeline_exec_scope) {
+        op->attr_key == attr::pipeline_exec_scope ||
+        op->attr_key == attr::device_scope) {
       return SplitDeviceFunc(s);
     }
     return IRMutator::Mutate_(op, s);

tests/python/unittest/test_pass_decorate_device_scope.py

+import tvm
+
+def test_decorate_device():
+    m = tvm.var('m')
+    l = tvm.var('l')
+    A = tvm.placeholder((m, l), name='A')
+
+    A1 = tvm.compute((m, l), lambda i, j: A[i, j], name='A1')
+    A2 = tvm.compute((m, l), lambda i, j: A1[i, j] + 3, name='A2')
+
+    s = tvm.create_schedule(A2.op)
+    xo, xi = s[A2].split(A2.op.axis[0], factor=8)
+    s[A1].compute_at(s[A2], xo)
+    s[A1].set_scope("shared")
+
+    bounds = tvm.schedule.InferBound(s)
+    stmt = tvm.schedule.ScheduleOps(s, bounds)
+    stmt1 = tvm.ir_pass.Simplify(stmt)
+    stmt2 = tvm.ir_pass.DecorateDeviceScope(stmt1)
+    assert isinstance(stmt2, tvm.stmt.AttrStmt)
+    assert stmt2.attr_key == "device_scope"
+    assert stmt1 == stmt2.body
+    
+if __name__ == "__main__":
+    test_decorate_device()
+