cxxrtl: Fix value::shl

tests/cxxrtl/.gitignore

@@ -0,0 +1 @@
+cxxrtl-test-*

tests/cxxrtl/run-test.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+set -ex
+
+run_subtest () {
+    local subtest=$1; shift
+
+    ${CC:-gcc} -std=c++11 -o cxxrtl-test-${subtest} -I../../backends/cxxrtl/runtime test_${subtest}.cc -lstdc++
+    ./cxxrtl-test-${subtest}
+}
+
+run_subtest value

tests/cxxrtl/test_value.cc

@@ -0,0 +1,15 @@
+#include <cassert>
+#include <cstdint>
+
+#include "cxxrtl/cxxrtl.h"
+
+int main()
+{
+    {
+        // shl exceeding Bits should be masked
+        cxxrtl::value<6> a(1u);
+        cxxrtl::value<6> b(8u);
+        cxxrtl::value<6> c = a.shl(b);
+        assert(c.get<uint64_t>() == 0);
+    }
+}