Index: lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -182,6 +182,11 @@
         cl::init(true), cl::Hidden);
 
 #ifndef NDEBUG
+static cl::opt<int>
+ViewDAGBasicBlockNumber("filter-view-dags", cl::Hidden,
+                        cl::desc("Only display the basic block that matches "
+                                 "this number for all view-dags* options"),
+                        cl::init(-1));
 static cl::opt<bool>
 ViewDAGCombine1("view-dag-combine1-dags", cl::Hidden,
           cl::desc("Pop up a window to show dags before the first "
@@ -658,6 +663,7 @@
   std::string BlockName;
   int BlockNumber = -1;
   (void)BlockNumber;
+  bool MatchFilterBB = false; (void)MatchFilterBB;
 #ifdef NDEBUG
   if (ViewDAGCombine1 || ViewLegalizeTypesDAGs || ViewLegalizeDAGs ||
       ViewDAGCombine2 || ViewDAGCombineLT || ViewISelDAGs || ViewSchedDAGs ||
@@ -665,13 +671,16 @@
 #endif
   {
     BlockNumber = FuncInfo->MBB->getNumber();
+    MatchFilterBB = (ViewDAGBasicBlockNumber == -1 ||
+                     ViewDAGBasicBlockNumber == BlockNumber);
     BlockName = MF->getName().str() + ":" +
                 FuncInfo->MBB->getBasicBlock()->getName().str();
   }
-  DEBUG(dbgs() << "Initial selection DAG: BB#" << BlockNumber
-        << " '" << BlockName << "'\n"; CurDAG->dump());
+  dbgs() << "Initial selection DAG: BB#" << BlockNumber
+        << " '" << BlockName << "'\n";
 
-  if (ViewDAGCombine1) CurDAG->viewGraph("dag-combine1 input for " + BlockName);
+  if (ViewDAGCombine1 && MatchFilterBB)
+    CurDAG->viewGraph("dag-combine1 input for " + BlockName);
 
   // Run the DAG combiner in pre-legalize mode.
   {
@@ -684,8 +693,8 @@
 
   // Second step, hack on the DAG until it only uses operations and types that
   // the target supports.
-  if (ViewLegalizeTypesDAGs) CurDAG->viewGraph("legalize-types input for " +
-                                               BlockName);
+  if (ViewLegalizeTypesDAGs && MatchFilterBB)
+    CurDAG->viewGraph("legalize-types input for " + BlockName);
 
   bool Changed;
   {
@@ -699,7 +708,7 @@
   CurDAG->NewNodesMustHaveLegalTypes = true;
 
   if (Changed) {
-    if (ViewDAGCombineLT)
+    if (ViewDAGCombineLT && MatchFilterBB)
       CurDAG->viewGraph("dag-combine-lt input for " + BlockName);
 
     // Run the DAG combiner in post-type-legalize mode.
@@ -725,7 +734,7 @@
       CurDAG->LegalizeTypes();
     }
 
-    if (ViewDAGCombineLT)
+    if (ViewDAGCombineLT && MatchFilterBB)
       CurDAG->viewGraph("dag-combine-lv input for " + BlockName);
 
     // Run the DAG combiner in post-type-legalize mode.
@@ -739,7 +748,8 @@
           << BlockNumber << " '" << BlockName << "'\n"; CurDAG->dump());
   }
 
-  if (ViewLegalizeDAGs) CurDAG->viewGraph("legalize input for " + BlockName);
+  if (ViewLegalizeDAGs && MatchFilterBB)
+    CurDAG->viewGraph("legalize input for " + BlockName);
 
   {
     NamedRegionTimer T("DAG Legalization", GroupName, TimePassesIsEnabled);
@@ -749,7 +759,8 @@
   DEBUG(dbgs() << "Legalized selection DAG: BB#" << BlockNumber
         << " '" << BlockName << "'\n"; CurDAG->dump());
 
-  if (ViewDAGCombine2) CurDAG->viewGraph("dag-combine2 input for " + BlockName);
+  if (ViewDAGCombine2 && MatchFilterBB)
+    CurDAG->viewGraph("dag-combine2 input for " + BlockName);
 
   // Run the DAG combiner in post-legalize mode.
   {
@@ -763,7 +774,8 @@
   if (OptLevel != CodeGenOpt::None)
     ComputeLiveOutVRegInfo();
 
-  if (ViewISelDAGs) CurDAG->viewGraph("isel input for " + BlockName);
+  if (ViewISelDAGs && MatchFilterBB)
+    CurDAG->viewGraph("isel input for " + BlockName);
 
   // Third, instruction select all of the operations to machine code, adding the
   // code to the MachineBasicBlock.
@@ -775,7 +787,8 @@
   DEBUG(dbgs() << "Selected selection DAG: BB#" << BlockNumber
         << " '" << BlockName << "'\n"; CurDAG->dump());
 
-  if (ViewSchedDAGs) CurDAG->viewGraph("scheduler input for " + BlockName);
+  if (ViewSchedDAGs && MatchFilterBB)
+    CurDAG->viewGraph("scheduler input for " + BlockName);
 
   // Schedule machine code.
   ScheduleDAGSDNodes *Scheduler = CreateScheduler();
@@ -785,7 +798,7 @@
     Scheduler->Run(CurDAG, FuncInfo->MBB);
   }
 
-  if (ViewSUnitDAGs) Scheduler->viewGraph();
+  if (ViewSUnitDAGs && MatchFilterBB) Scheduler->viewGraph();
 
   // Emit machine code to BB.  This can change 'BB' to the last block being
   // inserted into.