[Mlir-commits] [mlir] Revert "[MLIR][Mem2Reg] Add support for memref.alloca_scope" (PR #215354)

[Kewen Meng]

https://github.com/Kewen12 created https://github.com/llvm/llvm-project/pull/215354

Reverts llvm/llvm-project#214221

unblock bots: 
https://lab.llvm.org/buildbot/#/builders/203
https://lab.llvm.org/buildbot/#/builders/226
https://lab.llvm.org/buildbot/#/builders/234/builds/1876

>From 09b1ed1744781695d043902402be3919101e13c6 Mon Sep 17 00:00:00 2001
From: Kewen Meng <Kewen.Meng at amd.com>
Date: Mon, 10 Aug 2026 10:59:13 -0700
Subject: [PATCH] Revert "[MLIR][Mem2Reg] Add support for memref.alloca_scope
 (#214221)"

This reverts commit 7214eb03c28238b89b6ba7e6d56b67359d6cf79e.
---
 .../mlir/Dialect/MemRef/IR/MemRefOps.td       | 15 ++++---
 .../Dialect/MemRef/IR/MemRefMemorySlot.cpp    | 40 +------------------
 mlir/test/Dialect/MemRef/mem2reg.mlir         | 21 ----------
 3 files changed, 8 insertions(+), 68 deletions(-)

diff --git a/mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td b/mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td
index fb4506b92f5d9..8f530b2dbd62e 100644
--- a/mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td
+++ b/mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td
@@ -419,14 +419,13 @@ def MemRef_AllocaOp : AllocLikeOp<"alloca", AutomaticAllocationScopeResource,[
 // AllocaScopeOp
 //===----------------------------------------------------------------------===//
 
-def MemRef_AllocaScopeOp
-    : MemRef_Op<"alloca_scope",
-                [AutomaticAllocationScope,
-                 DeclareOpInterfaceMethods<
-                     RegionBranchOpInterface, ["getSuccessorInputs"]>,
-                 DeclareOpInterfaceMethods<PromotableRegionOpInterface>,
-                 SingleBlockImplicitTerminator<"AllocaScopeReturnOp">,
-                 RecursiveMemoryEffects, NoRegionArguments]> {
+def MemRef_AllocaScopeOp : MemRef_Op<"alloca_scope",
+      [AutomaticAllocationScope,
+       DeclareOpInterfaceMethods<RegionBranchOpInterface, [
+          "getSuccessorInputs"]>,
+       SingleBlockImplicitTerminator<"AllocaScopeReturnOp">,
+       RecursiveMemoryEffects,
+       NoRegionArguments]> {
   let summary = "explicitly delimited scope for stack allocation";
   let description = [{
     The `memref.alloca_scope` operation represents an explicitly-delimited
diff --git a/mlir/lib/Dialect/MemRef/IR/MemRefMemorySlot.cpp b/mlir/lib/Dialect/MemRef/IR/MemRefMemorySlot.cpp
index e4a66f3728ffd..6748e2cf71804 100644
--- a/mlir/lib/Dialect/MemRef/IR/MemRefMemorySlot.cpp
+++ b/mlir/lib/Dialect/MemRef/IR/MemRefMemorySlot.cpp
@@ -19,8 +19,8 @@
 #include "mlir/IR/Matchers.h"
 #include "mlir/IR/Value.h"
 #include "mlir/Interfaces/MemorySlotInterfaces.h"
-#include "mlir/Interfaces/Utils/MemorySlotUtils.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/TypeSwitch.h"
 #include "llvm/Support/ErrorHandling.h"
 
 using namespace mlir;
@@ -277,44 +277,6 @@ DeletionKind memref::StoreOp::rewire(const DestructurableMemorySlot &slot,
   return DeletionKind::Keep;
 }
 
-//===----------------------------------------------------------------------===//
-//  Interfaces for AllocaScopeOp
-//===----------------------------------------------------------------------===//
-
-bool memref::AllocaScopeOp::isRegionPromotable(const MemorySlot &slot,
-                                               Region *region,
-                                               bool hasValueStores) {
-  return true;
-}
-
-void memref::AllocaScopeOp::setupPromotion(
-    const MemorySlot &slot, Value reachingDef, bool hasValueStores,
-    llvm::SmallMapVector<Region *, Value, 2> &regionsToProcess) {
-  regionsToProcess.insert({&getRegion(), reachingDef});
-}
-
-Value memref::AllocaScopeOp::finalizePromotion(
-    const MemorySlot &slot, Value reachingDef, bool hasValueStores,
-    const llvm::DenseMap<Block *, Value> &reachingAtBlockEnd,
-    OpBuilder &builder) {
-  if (!hasValueStores)
-    return reachingDef;
-
-  IRRewriter rewriter(builder);
-
-  // Update the return terminator to return the newly defined reaching
-  // definition.
-  memoryslot::updateTerminator(&getRegion().back(), reachingDef,
-                               reachingAtBlockEnd);
-
-  SmallVector<Type> resultTypes(getResultTypes());
-  resultTypes.push_back(slot.elemType);
-
-  Operation *newOp =
-      memoryslot::replaceWithNewResults(rewriter, getOperation(), resultTypes);
-  return newOp->getResults().back();
-}
-
 //===----------------------------------------------------------------------===//
 //  Interfaces for destructurable types
 //===----------------------------------------------------------------------===//
diff --git a/mlir/test/Dialect/MemRef/mem2reg.mlir b/mlir/test/Dialect/MemRef/mem2reg.mlir
index 719b8b9acdb8f..8f937c4efe75e 100644
--- a/mlir/test/Dialect/MemRef/mem2reg.mlir
+++ b/mlir/test/Dialect/MemRef/mem2reg.mlir
@@ -309,24 +309,3 @@ func.func @two_consecutive_merge_points(%cond1: i1, %cond2: i1) -> i32 {
   // CHECK: return %[[RESULT]] : i32
   return %result : i32
 }
-
-// -----
-
-// Ensure that AllocaScopeOp does not block mem2reg.
-
-// CHECK-LABEL: func.func @alloca_scope
-func.func @alloca_scope() -> i32 {
-  %c0 = arith.constant 0 : i32
-  %alloca = memref.alloca() {alignment = 4 : i64} : memref<i32>
-  memref.store %c0, %alloca[] : memref<i32>
-  // CHECK:  %[[RET:.*]] = memref.alloca_scope
-  memref.alloca_scope  {
-    %c1 = arith.constant 1 : i32
-    memref.store %c1, %alloca[] : memref<i32>
-    // CHECK: %[[ONE:.*]] = arith.constant 1
-    // CHECK: memref.alloca_scope.return %[[ONE]]
-  }
-  %value = memref.load %alloca[] : memref<i32>
-  // CHECK: return %[[RET]]
-  return %value : i32
-}