Workaround for "illegal memory access" errors

Add debug functions to prevent the compiler from optimising out a
conditional check or access to an object.

Author: fwyzard

HeterogeneousCore/AlpakaInterface/interface/debug.h

@@ -0,0 +1,25 @@
+#ifndef HeterogeneousCore_AlpakaInterface_interface_debug_h
+#define HeterogeneousCore_AlpakaInterface_interface_debug_h
+
+#include "HeterogeneousCore/AlpakaInterface/interface/config.h"
+
+namespace ALPAKA_ACCELERATOR_NAMESPACE::debug {
+
+  [[nodiscard]] ALPAKA_FN_ACC inline bool always_true() {
+    volatile const bool flag = true;
+    return flag;
+  }
+
+  [[nodiscard]] ALPAKA_FN_ACC inline bool always_false() {
+    volatile const bool flag = false;
+    return flag;
+  }
+
+  ALPAKA_FN_ACC inline void do_not_optimise(const auto& arg) {
+    volatile const auto* ptr = &arg;
+    (void)*ptr;
+  }
+
+}  // namespace ALPAKA_ACCELERATOR_NAMESPACE::debug
+
+#endif  // HeterogeneousCore_AlpakaInterface_interface_debug_h

RecoTracker/PixelSeeding/plugins/alpaka/BrokenLineFit.dev.cc

@@ -7,6 +7,7 @@
 
 #include "DataFormats/TrackingRecHitSoA/interface/TrackingRecHitsSoA.h"
 #include "HeterogeneousCore/AlpakaInterface/interface/config.h"
+#include "HeterogeneousCore/AlpakaInterface/interface/debug.h"
 #include "RecoLocalTracker/SiPixelRecHits/interface/pixelCPEforDevice.h"
 #include "RecoTracker/PixelTrackFitting/interface/alpaka/BrokenLine.h"
 
@@ -182,6 +183,9 @@ namespace ALPAKA_ACCELERATOR_NAMESPACE {
                                   double *__restrict__ phits,
                                   float *__restrict__ phits_ge,
                                   double *__restrict__ pfast_fit) const {
+      // workaround for #47808
+      debug::do_not_optimise(results_view);
+
       ALPAKA_ASSERT_ACC(results_view.pt());
       ALPAKA_ASSERT_ACC(results_view.eta());
       ALPAKA_ASSERT_ACC(results_view.chi2());

RecoVertex/PixelVertexFinding/plugins/alpaka/clusterTracksByDensity.h

@@ -10,6 +10,7 @@
 #include "DataFormats/VertexSoA/interface/ZVertexSoA.h"
 #include "HeterogeneousCore/AlpakaInterface/interface/HistoContainer.h"
 #include "HeterogeneousCore/AlpakaInterface/interface/config.h"
+#include "HeterogeneousCore/AlpakaInterface/interface/debug.h"
 #include "HeterogeneousCore/AlpakaInterface/interface/warpsize.h"
 #include "HeterogeneousCore/AlpakaInterface/interface/workdivision.h"
 #include "RecoVertex/PixelVertexFinding/interface/PixelVertexWorkSpaceLayout.h"
@@ -31,6 +32,9 @@ namespace ALPAKA_ACCELERATOR_NAMESPACE::vertexFinder {
                                                              float errmax,  // max error to be "seed"
                                                              float chi2max  // max normalized distance to cluster
   ) {
+    // workaround for #47808
+    debug::do_not_optimise(ws);
+
     constexpr bool verbose = false;
 
     if constexpr (verbose) {

RecoVertex/PixelVertexFinding/plugins/alpaka/clusterTracksDBSCAN.h

@@ -10,6 +10,7 @@
 #include "DataFormats/VertexSoA/interface/ZVertexSoA.h"
 #include "HeterogeneousCore/AlpakaInterface/interface/HistoContainer.h"
 #include "HeterogeneousCore/AlpakaInterface/interface/config.h"
+#include "HeterogeneousCore/AlpakaInterface/interface/debug.h"
 #include "HeterogeneousCore/AlpakaInterface/interface/workdivision.h"
 #include "RecoVertex/PixelVertexFinding/interface/PixelVertexWorkSpaceLayout.h"
 
@@ -30,6 +31,9 @@ namespace ALPAKA_ACCELERATOR_NAMESPACE::vertexFinder {
                                   float errmax,  // max error to be "seed"
                                   float chi2max  // max normalized distance to cluster
     ) const {
+      // workaround for #47808
+      debug::do_not_optimise(ws);
+
       constexpr bool verbose = false;
 
       if constexpr (verbose) {