🐛 Harden MLIR constant folding

mlir/include/mlir/Dialect/MQT/Utils/ConstantFolding.h

@@ -21,7 +21,7 @@ namespace mlir::mqt {
 /// Convert a floating-point or integer attribute to a double.
 [[nodiscard]] std::optional<double> attributeToDouble(Attribute attr);
 
-/// Convert a direct arithmetic constant to a double.
+/// Convert a direct constant-like value to a double.
 [[nodiscard]] std::optional<double> valueToDouble(Value value);
 
 /**

mlir/lib/Dialect/MQT/Utils/ConstantFolding.cpp

@@ -11,7 +11,6 @@
 #include "mlir/Dialect/MQT/Utils/ConstantFolding.h"
 
 #include <llvm/ADT/SmallVector.h>
-#include <mlir/Dialect/Arith/IR/Arith.h>
 #include <mlir/IR/Attributes.h>
 #include <mlir/IR/BuiltinAttributes.h>
 #include <mlir/IR/Matchers.h>
@@ -41,11 +40,11 @@ std::optional<double> attributeToDouble(Attribute attr) {
 }
 
 std::optional<double> valueToDouble(Value value) {
-  auto constantOp = value.getDefiningOp<arith::ConstantOp>();
-  if (!constantOp) {
+  Attribute attr;
+  if (!matchPattern(value, m_Constant(&attr))) {
     return std::nullopt;
   }
-  return attributeToDouble(constantOp.getValue());
+  return attributeToDouble(attr);
 }
 
 std::optional<Attribute>

mlir/unittests/Dialect/MQT/Utils/CMakeLists.txt

@@ -8,8 +8,9 @@
 
 set(mqt_utils_target mqt-core-mlir-unittests-mqt-utils)
 add_executable(${mqt_utils_target} test_constant_folding.cpp test_gate_powering.cpp)
-target_link_libraries(${mqt_utils_target} PRIVATE GTest::gtest_main MLIRArithDialect
-                                                  MLIRFuncDialect MLIRIR MLIRMQTUtils)
+target_link_libraries(
+  ${mqt_utils_target} PRIVATE GTest::gtest_main MLIRArithDialect MLIRFuncDialect MLIRIndexDialect
+                              MLIRIR MLIRMQTUtils)
 mqt_mlir_configure_unittest_target(${mqt_utils_target})
 
 gtest_discover_tests(${mqt_utils_target} PROPERTIES LABELS mqt-mlir-unittests DISCOVERY_TIMEOUT 60)

mlir/unittests/Dialect/MQT/Utils/test_constant_folding.cpp

@@ -13,6 +13,8 @@
 #include <gtest/gtest.h>
 #include <mlir/Dialect/Arith/IR/Arith.h>
 #include <mlir/Dialect/Func/IR/FuncOps.h>
+#include <mlir/Dialect/Index/IR/IndexDialect.h>
+#include <mlir/Dialect/Index/IR/IndexOps.h>
 #include <mlir/IR/Builders.h>
 #include <mlir/IR/BuiltinOps.h>
 #include <mlir/IR/BuiltinTypes.h>
@@ -39,7 +41,8 @@ class ConstantFoldingTest : public ::testing::Test {
   std::unique_ptr<ImplicitLocOpBuilder> builder;
 
   void SetUp() override {
-    context.loadDialect<arith::ArithDialect, func::FuncDialect>();
+    context.loadDialect<arith::ArithDialect, func::FuncDialect,
+                        index::IndexDialect>();
 
     auto loc = FileLineColLoc::get(&context, "<utils-test-builder>", 1, 1);
     module = ModuleOp::create(loc);
@@ -66,6 +69,13 @@ TEST_F(ConstantFoldingTest, valueToDoubleCastFromInteger) {
   EXPECT_DOUBLE_EQ(*stdValue, 42.0);
 }
 
+TEST_F(ConstantFoldingTest, valueToDoubleConstantLike) {
+  auto op = index::ConstantOp::create(*builder, 42);
+  const auto stdValue = mlir::mqt::valueToDouble(op.getResult());
+  ASSERT_TRUE(stdValue.has_value());
+  EXPECT_DOUBLE_EQ(*stdValue, 42.0);
+}
+
 TEST_F(ConstantFoldingTest, valueToDoubleCastFromNegativeInteger) {
   auto op =
       arith::ConstantOp::create(*builder, builder->getSI32IntegerAttr(-123));