[Mlir-commits] [mlir] [mlir][dataflow] Add visitBranchRegionArgument interface to SparseBackwardDataFlowAnalysis and apply it in LivenessAnalysis/RemoveDeadValues (PR #169816)

[Oleksandr Alex Zinenko]

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@@ -244,24 +224,12 @@ void LivenessAnalysis::visitBranchOperand(OpOperand &operand) {
     Liveness *operandLiveness = getLatticeElement(operand.get());
     LDBG() << "Marking branch operand live: " << operand.get();
     propagateIfChanged(operandLiveness, operandLiveness->markLive());
-    for (BlockArgument argument : argumentNotOperand) {
-      Liveness *argumentLiveness = getLatticeElement(argument);
-      LDBG() << "Marking RegionBranchOp's argument live: " << argument;
-      // TODO: this is overly conservative: we should be able to eliminate
-      // unused values in a RegionBranchOpInterface operation but that may
-      // requires removing operation results which is beyond current
-      // capabilities of this pass right now.
-      propagateIfChanged(argumentLiveness, argumentLiveness->markLive());
-    }
   }
 
   // Now that we have checked for memory-effecting ops in the blocks of concern,
   // we will simply visit the op with this non-forwarded operand to potentially
   // mark it "live" due to type (1.a/3) liveness.
   SmallVector<Liveness *, 4> operandLiveness;
-  operandLiveness.push_back(getLatticeElement(operand.get()));
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ftynse wrote:

Fair enough. What was surprising to me is that no tests seem to fail because of this. Let's keep this line in this patch so we can clearly, and revert if needed, the effect of each of them. All this logic is quite involved so it's better to do one step at a time.

https://github.com/llvm/llvm-project/pull/169816