[GitHub] [tvm] FranckQC commented on a diff in pull request #11574: [TIR] CSE pass : Restrict the equivalence to be decided by a normal form - avoids comparison of terms

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

FranckQC commented on code in PR #11574:
URL: https://github.com/apache/tvm/pull/11574#discussion_r890353098


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src/tir/transforms/common_subexpr_elim.cc:
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@@ -120,6 +120,39 @@ bool CommonSubexpressionEliminator::CanContainEligibleComputations(const PrimExp
   return true;
 }
 
+/*!
+ * \brief Implements an order on pairs (expression,frequency). First attempts to compare them
+          using the size of the expression. If the is the same, decides something else still
+          deterministic.
+ * \param a The first pair
+ * \param b The second pair
+ * \return A boolean telling if the first pair `a` comes before the second pair `b`
+ * \note We need this order to be deterministic in order to have a fully deterministic pass,
+ *       as we will deal with elements that are coming from a hashtable, but the order in which
+ *       they appeared in the hashtable was based on some runtime addresses, so it can potentially
+ *       change with every execution.
+ */
+bool CommonSubexpressionEliminator::OrderOnExprAndFrequency(std::pair<PrimExpr, size_t> a,
+                                                            std::pair<PrimExpr, size_t> b) {
+  size_t a_size = CalculateExprComplexity(a.first);
+  size_t b_size = CalculateExprComplexity(b.first);
+
+  // Criteria 1 - Size of the expression comes first
+  // `a` comes before `b` if the size of `a` is bigger
+  if (a_size > b_size) return true;
+  // `a` does NOT come before `b` if the size of `b` is bigger
+  else if (b_size > a_size)
+    return false;

Review Comment:
   Sure, will do. Thank you!



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