[GitHub] [incubator-tvm] icemelon9 commented on a change in pull request #5144: [Relay][VM] Memory planner (part 1)

[GitBox <gi...@apache.org>]

icemelon9 commented on a change in pull request #5144: [Relay][VM] Memory planner (part 1)
URL: https://github.com/apache/incubator-tvm/pull/5144#discussion_r406963966
 
 

 ##########
 File path: python/tvm/relay/def_use.py
 ##########
 @@ -0,0 +1,42 @@
+from . import expr
+from .expr_functor import ExprVisitor
+from .analysis import free_vars
+
+import attr
+from typing import List, Dict
+
+@attr.s(auto_attribs=True)
+class DefUse:
+    defn: expr.Var
+    uses: List[expr.Expr]
+
+class DefUseAnalysis(ExprVisitor):
+    def __init__(self):
+        super().__init__()
+        self.results: Dict[expr.Var, DefUse] = {}
+
+    def visit_function(self, func):
+        for param in func.params:
+            self.results[param] = DefUse(param, [])
+        super().visit_function(func)
+
+    def visit_let(self, let):
+        while isinstance(let, expr.Let):
+            du = DefUse(let.var, [])
+            self.results[let.var] = du
+            # Find all variables used in RHS.
+            self.visit(let.value)
+            used_vars = free_vars(let.value)
+            for uvar in used_vars:
+                self.results[uvar].uses.append(let.value)
+            let = let.body
+
+        # Find all variables used in body.
+        used_vars = free_vars(let)
 
 Review comment:
   Should this be `free_vars(let.body)`?

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