Test: Unorderded Map Access

This demonstrates two issues with `std::unordered_map`:
- `at()` fails to compile
- `operator[]` has a memory leak

Author: ax3l

enzyme/test/Integration/ReverseMode/stl_umap.cpp

@@ -0,0 +1,82 @@
+// RUN: %clang++ -std=c++11 -fno-exceptions -ffast-math -O0 %s -S -emit-llvm -o - | %opt - %OPloadEnzyme %enzyme -S | %lli -
+// RUN: %clang++ -std=c++11 -fno-exceptions -ffast-math -O1 %s -S -emit-llvm -o - | %opt - %OPloadEnzyme %enzyme -S | %lli -
+// RUN: %clang++ -std=c++11 -fno-exceptions -ffast-math -O2 %s -S -emit-llvm -o - | %opt - %OPloadEnzyme %enzyme -S | %lli -
+// RUN: %clang++ -std=c++11 -fno-exceptions -ffast-math -O3 %s -S -emit-llvm -o - | %opt - %OPloadEnzyme %enzyme -S | %lli -
+
+#include "../test_utils.h"
+
+#include <cmath>
+#include <string>
+#include <unordered_map>
+
+
+extern double __enzyme_autodiff(void*, double);
+
+std::unordered_map<std::string, double>
+fill_umap(double x, double y) {
+    std::unordered_map<std::string, double> data;
+
+    data["alpha_x"] = x*x + y;
+    data["alpha_y"] = y*y + 2.;
+
+    return data;
+}
+
+double compute_umap_op(double r) {
+    double x = std::sqrt(r);
+    double y = std::log(r);
+
+    std::unordered_map<std::string, double> data = fill_umap(x, y);
+
+    // FIXME: memory leak
+    // https://github.com/EnzymeAD/Enzyme/issues/2367#issuecomment-3025856672
+    return data["alpha_x"];
+}
+
+/* FIXME
+double compute_umap_at(double r) {
+    double x = std::sqrt(r);
+    double y = std::log(r);
+
+    std::unordered_map<std::string, double> const data = fill_umap(x, y);
+
+    // FIXME: fails to compile
+    // https://fwd.gymni.ch/oGas9k
+    return data.at("alpha_x");
+}
+*/
+
+void test_umap() {
+    double q1_k = -3.0;
+
+    // operator[]
+    {
+        // normal
+        double const alpha_x = compute_umap_op(q1_k);
+        APPROX_EQ( alpha_x, 4.098612, 1e-6);
+
+        // diff
+        double ddx = __enzyme_autodiff((void*) compute_umap_op, q1_k);
+        APPROX_EQ( ddx, 1.333333, 1e-6);
+    }
+
+    // at()
+    /* FIXME
+    {
+        // normal
+        double const alpha_x = compute_umap_at(q1_k);
+        APPROX_EQ( alpha_x, 4.098612, 1e-6);
+
+        // diff
+        double ddx = __enzyme_autodiff((void*) compute_umap_at, q1_k);
+        APPROX_EQ( ddx, 1.333333, 1e-6);
+    }*/
+}
+
+int main() {
+    test_umap();
+
+    return 0;
+}
+
+