[Mlir-commits] [mlir] [mlir][RemoveDeadValues] Use `SymbolUserMap` to avoid quadratic symbol lookups (PR #205448)

[Mehdi Amini]

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@@ -770,6 +766,13 @@ void RemoveDeadValues::runOnOperation() {
   auto &la = getAnalysis<RunLivenessAnalysis>();
   Operation *module = getOperation();
 
+  // Build a symbol user map once up front so that processFuncOp can look up the
+  // callers of each function in O(1). Otherwise, each call would walk the
+  // entire module to find the callers, making the pass O(numFunctions *
+  // numOperations).
+  SymbolTableCollection symbolTableCollection;
+  SymbolUserMap symbolUserMap(symbolTableCollection, module);
+
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joker-eph wrote:

Mmm, I see your note in the description:

> This is behavior-preserving: the map is read only during the mutation-free collection walk, and all IR erasure happens afterwards in cleanUpDeadVals, so the map cannot become stale while it is in use.

https://github.com/llvm/llvm-project/pull/205448