[clang] [CIR] Emit allocas into the proper lexical scope (PR #132468)

[Andy Kaylor via cfe-commits]

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@@ -0,0 +1,81 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "PassDetail.h"
+#include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/IR/PatternMatch.h"
+#include "mlir/Support/LogicalResult.h"
+#include "mlir/Transforms/DialectConversion.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+#include "clang/CIR/Dialect/IR/CIRDialect.h"
+#include "clang/CIR/Dialect/Passes.h"
+#include "clang/CIR/MissingFeatures.h"
+#include "llvm/Support/TimeProfiler.h"
+
+using namespace mlir;
+using namespace cir;
+
+namespace {
+
+struct HoistAllocasPass : public HoistAllocasBase<HoistAllocasPass> {
+
+  HoistAllocasPass() = default;
+  void runOnOperation() override;
+};
+
+static void process(mlir::ModuleOp mod, cir::FuncOp func) {
+  if (func.getRegion().empty())
+    return;
+
+  // Hoist all static allocas to the entry block.
+  mlir::Block &entryBlock = func.getRegion().front();
+  llvm::SmallVector<cir::AllocaOp> allocas;
+  func.getBody().walk([&](cir::AllocaOp alloca) {
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andykaylor wrote:

I'm not sure I can do that because the loop below is moving allocas. Hoisting them midwalk could disrupt the walking process.

https://github.com/llvm/llvm-project/pull/132468