[Mlir-commits] [mlir] [MLIR] Removing dead values for branches (PR #117501)

[Renat Idrisov]

================
@@ -563,6 +575,48 @@ static void cleanRegionBranchOp(RegionBranchOpInterface regionBranchOp,
   dropUsesAndEraseResults(regionBranchOp.getOperation(), resultsToKeep.flip());
 }
 
+// 1. Iterate over each successor block of the given BranchOpInterface
+// operation.
+// 2. For each successor block:
+//    a. Retrieve the operands passed to the successor.
+//    b. Use the provided liveness analysis (`RunLivenessAnalysis`) to determine
+//    which
+//       operands are live in the successor block.
+//    c. Mark each operand as live or dead based on the analysis.
+// 3. Remove dead operands from the branch operation and arguments accordingly
+
+static void cleanBranchOp(BranchOpInterface branchOp, RunLivenessAnalysis &la) {
----------------
parsifal-47 wrote:

My first idea was to make a recursive function, but I checked other pieces of this pass and I saw no recursion. It looks like it is applied till stable point is reached and no more values getting deleted. In iterative fashion. If doing recursively, we need to check for maximal depth and cyclic dependencies. And do that for any kinds of operations. Do you have an advice @joker-eph ?

https://github.com/llvm/llvm-project/pull/117501