From 6f5324057ec371d3468c95a18baf35adc7f01993 Mon Sep 17 00:00:00 2001
From: Simon Hofmann <simon.t.hofmann@tum.de>
Date: Mon, 31 Aug 2026 17:36:14 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Respect=20isolation=20when=20hoi?=
 =?UTF-8?q?sting=20static=20qubits?=
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Keep qc.static operations inside their nearest IsolatedFromAbove scope so cleanup does not create invalid captures.

Assisted-by: GPT-5.6 Sol via Codex
---
 .../QC/IR/QubitManagement/DeallocOp.cpp       |  4 +++-
 mlir/unittests/Dialect/QC/IR/test_qc_ir.cpp   | 24 +++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/mlir/lib/Dialect/QC/IR/QubitManagement/DeallocOp.cpp b/mlir/lib/Dialect/QC/IR/QubitManagement/DeallocOp.cpp
index 26b6f7b6f6..b8559de464 100644
--- a/mlir/lib/Dialect/QC/IR/QubitManagement/DeallocOp.cpp
+++ b/mlir/lib/Dialect/QC/IR/QubitManagement/DeallocOp.cpp
@@ -53,7 +53,9 @@ struct HoistStaticQubit final : OpRewritePattern<StaticOp> {
   LogicalResult matchAndRewrite(StaticOp op,
                                 PatternRewriter& rewriter) const override {
     auto funcOp = op->getParentOfType<func::FuncOp>();
-    if (!funcOp || op->getBlock() == &funcOp.getBody().front()) {
+    if (!funcOp ||
+        op->getParentWithTrait<OpTrait::IsIsolatedFromAbove>() != funcOp ||
+        op->getBlock() == &funcOp.getBody().front()) {
       return failure();
     }
     rewriter.moveOpBefore(op, &funcOp.getBody().front(),
diff --git a/mlir/unittests/Dialect/QC/IR/test_qc_ir.cpp b/mlir/unittests/Dialect/QC/IR/test_qc_ir.cpp
index daaceed3fa..fa17cf9476 100644
--- a/mlir/unittests/Dialect/QC/IR/test_qc_ir.cpp
+++ b/mlir/unittests/Dialect/QC/IR/test_qc_ir.cpp
@@ -181,6 +181,30 @@ TEST_F(QCTest, CleanupHoistsAndCoalescesStaticQubits) {
   EXPECT_EQ(staticOps, 2U);
 }
 
+TEST_F(QCTest, CleanupDoesNotHoistStaticQubitsAcrossIsolationBoundaries) {
+  auto module = parseSourceString<ModuleOp>(R"mlir(
+    module {
+      func.func @main() {
+        "builtin.module"() ({
+          %q = qc.static 0 : !qc.qubit
+          qc.x %q : !qc.qubit
+        }) : () -> ()
+        return
+      }
+    }
+  )mlir",
+                                            context.get());
+  ASSERT_TRUE(module);
+  ASSERT_TRUE(succeeded(verify(*module)));
+  ASSERT_TRUE(succeeded(runQCCleanupPipeline(*module)));
+  ASSERT_TRUE(succeeded(verify(*module)));
+
+  StaticOp staticOp;
+  module->walk([&](StaticOp op) { staticOp = op; });
+  ASSERT_TRUE(staticOp);
+  EXPECT_TRUE(isa<ModuleOp>(staticOp->getParentOp()));
+}
+
 TEST_F(QCTest, BuilderRejectsMixedStaticAndDynamicQubitAllocationModes) {
   EXPECT_DEATH(
       {