GPUTracking: replace the merger's goto with a flag

MSL supports neither goto nor labels. The label sat at the end of the loop body,
so each jump was a continue for the outer loop that could not be written as one
because it was issued from an inner loop. The flag is set there instead, breaks
out of the loop it was raised in, and continues the outer one; where the jump
came from two levels down it breaks twice.

The k loop is left early exactly as before, and nothing between the old jumps
and the old label ran then either.

Author: ktf

GPU/GPUTracking/Merger/GPUTPCGMMerger.cxx

@@ -1201,6 +1201,7 @@ GPUd() void GPUTPCGMMerger::ResolveMergeSectors(GPUResolveSharedMemory& smem, in
       // PrintMergeGraph(track1, std::cout);
       // PrintMergeGraph(track2, std::cout);
 
+      bool nextTrack = false;
       while (track2->PrevSegmentNeighbour() >= 0) {
         track2 = &mSectorTrackInfos[track2->PrevSegmentNeighbour()];
       }
@@ -1211,26 +1212,41 @@ GPUd() void GPUTPCGMMerger::ResolveMergeSectors(GPUResolveSharedMemory& smem, in
         while (track1->PrevSegmentNeighbour() >= 0) {
           track1 = &mSectorTrackInfos[track1->PrevSegmentNeighbour()];
           if (track1 == track2) {
-            goto NextTrack;
+            nextTrack = true;
+            break;
           }
         }
+        if (nextTrack) {
+          continue;
+        }
         GPUCommonAlgorithm::swap(track1, track1Base);
         for (int32_t k = 0; k < 2; k++) {
           GPUTPCGMSectorTrack* tmp = track1Base;
           while (tmp->Neighbour(k) >= 0) {
             tmp = &mSectorTrackInfos[tmp->Neighbour(k)];
             if (tmp == track2) {
-              goto NextTrack;
+              nextTrack = true;
+              break;
             }
           }
+          if (nextTrack) {
+            break;
+          }
+        }
+        if (nextTrack) {
+          continue;
         }
 
         while (track1->NextSegmentNeighbour() >= 0) {
           track1 = &mSectorTrackInfos[track1->NextSegmentNeighbour()];
           if (track1 == track2) {
-            goto NextTrack;
+            nextTrack = true;
+            break;
           }
         }
+        if (nextTrack) {
+          continue;
+        }
       } else {
         while (track1->PrevSegmentNeighbour() >= 0) {
           track1 = &mSectorTrackInfos[track1->PrevSegmentNeighbour()];
@@ -1244,9 +1260,16 @@ GPUd() void GPUTPCGMMerger::ResolveMergeSectors(GPUResolveSharedMemory& smem, in
           while (tmp->Neighbour(k) >= 0) {
             tmp = &mSectorTrackInfos[tmp->Neighbour(k)];
             if (tmp == track2) {
-              goto NextTrack;
+              nextTrack = true;
+              break;
             }
           }
+          if (nextTrack) {
+            break;
+          }
+        }
+        if (nextTrack) {
+          continue;
         }
 
         float z1min, z1max, z2min, z2max;
@@ -1318,7 +1341,6 @@ GPUd() void GPUTPCGMMerger::ResolveMergeSectors(GPUResolveSharedMemory& smem, in
       }
       // GPUInfo("Result");
       // PrintMergeGraph(track1, std::cout);
-    NextTrack:;
     }
   }
 }