TrkDetDescrGeoModelCnv: Another file to optimize in the debug build.

Compile GMTreeBrower with optimization, even in the debug build. Otherwise, the Eigen operations are very slow. This speeds to the TrkVertexSeedFinderTools unit tests by over a factor of two.

Tracking/TrkDetDescr/TrkDetDescrGeoModelCnv/src/GMTreeBrowser.cxx

@@ -29,7 +29,16 @@
 #include "GeoModelKernel/GeoTubs.h"
 #include "GeoModelKernel/GeoVPhysVol.h"
 #include "GeoModelUtilities/GeoVisitVolumes.h"
-
+#include "CxxUtils/inline_hints.h"
+
+#if defined(FLATTEN)
+    // We compile this package with optimization, even in debug builds; otherwise,
+    // the heavy use of Eigen makes it too slow.  However, from here we may call
+    // to out-of-line Eigen code that is linked from other DSOs; in that case,
+    // it would not be optimized.  Avoid this by forcing all Eigen code
+    // to be inlined here if possible.
+    ATH_FLATTEN
+#endif
 int Trk::GMTreeBrowser::compareGeoVolumes(const GeoVPhysVol* gv1,
                                           const GeoVPhysVol* gv2,
                                           double tolerance, bool dumpInfo,
@@ -162,6 +171,14 @@ int Trk::GMTreeBrowser::compareGeoVolumes(const GeoVPhysVol* gv1,
     return diff;
 }
 
+#if defined(FLATTEN)
+    // We compile this package with optimization, even in debug builds; otherwise,
+    // the heavy use of Eigen makes it too slow.  However, from here we may call
+    // to out-of-line Eigen code that is linked from other DSOs; in that case,
+    // it would not be optimized.  Avoid this by forcing all Eigen code
+    // to be inlined here if possible.
+    ATH_FLATTEN
+#endif
 bool Trk::GMTreeBrowser::compareShapes(const GeoShape* sh1, const GeoShape* sh2,
                                        double tol) const {