fix Issue 14203 - Return of floating point values from extern(C++) member functions does not match dmc

src/dmd/target.d

@@ -715,6 +715,16 @@ extern (C++) struct Target
             else
                 return true;
         }
+        else if (global.params.isWindows &&
+                 !global.params.is64bit &&
+                 (tf.linkage == LINK.cpp || tf.linkage == LINK.pascal) &&
+                 tf.isfloating())
+        {
+            /* See DMC++ function exp2_retmethod()
+             * https://github.com/DigitalMars/Compiler/blob/master/dm/src/dmc/dexp2.d#L149
+             */
+            return true;
+        }
         else
         {
             //assert(sz <= 16);

test/runnable_cxx/extra-files/c14203.cpp

@@ -0,0 +1,2 @@
+
+float func1() { return 73; }

test/runnable_cxx/test14203.d

@@ -0,0 +1,22 @@
+// EXTRA_CPP_SOURCES: c14203.cpp
+
+
+/************************************************/
+
+// https://issues.dlang.org/show_bug.cgi?id=14203
+
+extern (C++) float func1();
+
+void test14203()
+{
+    assert(func1() == 73);
+}
+
+/************************************************/
+
+int main()
+{
+    test14203();
+
+    return 0;
+}