[Mlir-commits] [mlir] [mlir] Fix block merging (PR #102038)

[Christian Ulmann]

================
@@ -818,6 +918,108 @@ static LogicalResult mergeIdenticalBlocks(RewriterBase &rewriter,
   return success(anyChanged);
 }
 
+static LogicalResult dropRedundantArguments(RewriterBase &rewriter,
+                                            Block &block) {
+  SmallVector<size_t> argsToErase;
+
+  // Go through the arguments of the block.
+  for (auto [argIdx, blockOperand] : llvm::enumerate(block.getArguments())) {
+    bool sameArg = true;
+    Value commonValue;
+
+    // Go through the block predecessor and flag if they pass to the block
+    // different values for the same argument.
+    for (auto predIt = block.pred_begin(), predE = block.pred_end();
+         predIt != predE; ++predIt) {
+      auto branch = dyn_cast<BranchOpInterface>((*predIt)->getTerminator());
+      if (!branch) {
+        sameArg = false;
+        break;
+      }
+      unsigned succIndex = predIt.getSuccessorIndex();
+      SuccessorOperands succOperands = branch.getSuccessorOperands(succIndex);
+      auto branchOperands = succOperands.getForwardedOperands();
+      if (!commonValue) {
+        commonValue = branchOperands[argIdx];
+      } else {
+        if (branchOperands[argIdx] != commonValue) {
+          sameArg = false;
+          break;
+        }
+      }
----------------
Dinistro wrote:

```suggestion
      if (!commonValue) {
        commonValue = branchOperands[argIdx];
        continue;
      }
      if (branchOperands[argIdx] != commonValue) {
        sameArg = false;
        break;
      }
```
Might be easier to read.

https://github.com/llvm/llvm-project/pull/102038