[Mlir-commits] [mlir] 918b8f5 - [mlir][CSE] Pre-process trivially dead ops (NFC) (#191135)

[llvmlistbot at llvm.org]

Author: lonely eagle
Date: 2026-04-21T00:59:40+08:00
New Revision: 918b8f5ce3f8155b66b3ae39ee5335d7da3808d6

URL: https://github.com/llvm/llvm-project/commit/918b8f5ce3f8155b66b3ae39ee5335d7da3808d6
DIFF: https://github.com/llvm/llvm-project/commit/918b8f5ce3f8155b66b3ae39ee5335d7da3808d6.diff

LOG: [mlir][CSE] Pre-process trivially dead ops (NFC) (#191135)

This PR avoids calling `simplifyRegion` on dead region ops.
`simplifyRegion` attempts to perform CSE optimization on the ops within
the region, which is unnecessary for ops that are already trivially
dead.

Added: 
    

Modified: 
    mlir/lib/Transforms/CSE.cpp

Removed: 
    


################################################################################
diff  --git a/mlir/lib/Transforms/CSE.cpp b/mlir/lib/Transforms/CSE.cpp
index c91084ba96bb3..c426ac698b7ae 100644
--- a/mlir/lib/Transforms/CSE.cpp
+++ b/mlir/lib/Transforms/CSE.cpp
@@ -258,13 +258,6 @@ LogicalResult CSEDriver::simplifyOperation(ScopedMapTy &knownValues,
   if (op->hasTrait<OpTrait::IsTerminator>())
     return failure();
 
-  // If the operation is already trivially dead just add it to the erase list.
-  if (isOpTriviallyDead(op)) {
-    opsToErase.push_back(op);
-    ++numDCE;
-    return success();
-  }
-
   // Don't simplify operations with regions that have multiple blocks.
   // TODO: We need additional tests to verify that we handle such IR correctly.
   if (!llvm::all_of(op->getRegions(),
@@ -308,7 +301,16 @@ LogicalResult CSEDriver::simplifyOperation(ScopedMapTy &knownValues,
 
 void CSEDriver::simplifyBlock(ScopedMapTy &knownValues, Block *bb,
                               bool hasSSADominance) {
-  for (auto &op : *bb) {
+  for (auto &op : llvm::make_early_inc_range(*bb)) {
+    // If the operation is already trivially dead just add it to the erase list.
+    // This also avoids calling `simplifyRegion` on dead region ops
+    // unnecessarily.
+    if (isOpTriviallyDead(&op)) {
+      opsToErase.push_back(&op);
+      ++numDCE;
+      continue;
+    }
+
     // Most operations don't have regions, so fast path that case.
     if (op.getNumRegions() != 0) {
       // If this operation is isolated above, we can't process nested regions