[Mlir-commits] [mlir] [MLIR] Fix crash in RemoveDeadValues when terminator lacks RegionBranchTerminatorOpInterface (PR #175300)

[llvmlistbot at llvm.org]

https://github.com/nataliakokoromyti created https://github.com/llvm/llvm-project/pull/175300

The RemoveDeadValues pass was using cast<RegionBranchTerminatorOpInterface> which asserts that the terminator implements this interface. However, some dialects (like CIR) have region terminators that don't implement this interface, causing crashes.

This patch changes cast to dyn_cast and skips processing for terminators that don't implement RegionBranchTerminatorOpInterface.

Fixes #174502

>From 20c215a0df413e4110a7dcfcb22d327761eaf8a3 Mon Sep 17 00:00:00 2001
From: Natalia Kokoromyti <nataliakokoromyti at gmail.com>
Date: Sat, 10 Jan 2026 01:15:31 -0800
Subject: [PATCH] [MLIR] Fix crash in RemoveDeadValues when terminator lacks
 RegionBranchTerminatorOpInterface

The RemoveDeadValues pass was using cast<RegionBranchTerminatorOpInterface>
which asserts that the terminator implements this interface. However, some
dialects (like CIR) have region terminators that don't implement this
interface, causing crashes.

This patch changes cast to dyn_cast and skips processing for terminators
that don't implement RegionBranchTerminatorOpInterface.

Fixes #174502
---
 mlir/lib/Transforms/RemoveDeadValues.cpp | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/mlir/lib/Transforms/RemoveDeadValues.cpp b/mlir/lib/Transforms/RemoveDeadValues.cpp
index fc2c2acf8afd3..4d20abb415229 100644
--- a/mlir/lib/Transforms/RemoveDeadValues.cpp
+++ b/mlir/lib/Transforms/RemoveDeadValues.cpp
@@ -477,8 +477,10 @@ static void processRegionBranchOp(RegionBranchOpInterface regionBranchOp,
           if (region.empty())
             continue;
           // TODO: this isn't correct in face of multiple terminators.
-          auto terminator = cast<RegionBranchTerminatorOpInterface>(
+          auto terminator = dyn_cast<RegionBranchTerminatorOpInterface>(
               region.front().getTerminator());
+          if (!terminator)
+            continue;
           nonForwardedRets[terminator] =
               BitVector(terminator->getNumOperands(), true);
           for (const RegionSuccessor &successor : getSuccessors(terminator)) {
@@ -498,11 +500,17 @@ static void processRegionBranchOp(RegionBranchOpInterface regionBranchOp,
           DenseMap<Region *, BitVector> &argsToKeep, Region *region = nullptr) {
         Operation *terminator =
             region ? region->front().getTerminator() : nullptr;
-        RegionBranchPoint point =
+        auto terminatorIface =
             terminator
-                ? RegionBranchPoint(
-                      cast<RegionBranchTerminatorOpInterface>(terminator))
-                : RegionBranchPoint::parent();
+                ? dyn_cast<RegionBranchTerminatorOpInterface>(terminator)
+                : nullptr;
+        // If terminator doesn't implement RegionBranchTerminatorOpInterface,
+        // we can't analyze it, so skip.
+        if (terminator && !terminatorIface)
+          return;
+        RegionBranchPoint point =
+            terminatorIface ? RegionBranchPoint(terminatorIface)
+                            : RegionBranchPoint::parent();
 
         for (const RegionSuccessor &successor : getSuccessors(point)) {
           Region *successorRegion = successor.getSuccessor();
@@ -566,8 +574,10 @@ static void processRegionBranchOp(RegionBranchOpInterface regionBranchOp,
         for (Region &region : regionBranchOp->getRegions()) {
           if (region.empty())
             continue;
-          auto terminator = cast<RegionBranchTerminatorOpInterface>(
+          auto terminator = dyn_cast<RegionBranchTerminatorOpInterface>(
               region.front().getTerminator());
+          if (!terminator)
+            continue;
           for (const RegionSuccessor &successor : getSuccessors(terminator)) {
             Region *successorRegion = successor.getSuccessor();
             for (auto [opOperand, input] :