Fix PR26940 where compiles times regressed massively.

[chandlerc]

Summary

Patch by Jonas Paulsson. Original description:
Bugfix in buildSchedGraph() to make -dag-maps-huge-region work properly

I found that the reduction of the maps did in fact never happen in this
test case. This was because *all* the stores / loads were made with
addresses from arguments and they thus became "unknown" stores / loads.
Fixed by removing continue statements and making sure that the test for
reduction always takes place.

[echristo]

Sure, that seems reasonable.

-eric

[hfinkel]

In D18673#388699, @echristo wrote:

Sure, that seems reasonable.

I think so too.

-eric

lib/CodeGen/ScheduleDAGInstrs.cpp

if (MI->mayStore()) {
         // An unknown store depends on all stores and loads.
         addChainDependencies(SU, Stores);
         addChainDependencies(SU, NonAliasStores);
         addChainDependencies(SU, Loads);
         addChainDependencies(SU, NonAliasLoads);
 
         // Map this store to 'UnknownValue'.
         Stores.insert(SU, UnknownValue);
-        continue;
-      }
-
+      } else {
         // Add precise dependencies against all previously seen memory
         // accesses mapped to the same Value(s).
         for (auto &underlObj : Objs) {
           ValueType V = underlObj.getPointer();
           bool ThisMayAlias = underlObj.getInt();
 
           Value2SUsMap &stores_ = (ThisMayAlias ? Stores : NonAliasStores);
 
           // Add dependencies to previous stores and loads mapped to V.
           addChainDependencies(SU, stores_, V);
           addChainDependencies(SU, (ThisMayAlias ? Loads : NonAliasLoads), V);
 
           // Map this store to V.
           stores_.insert(SU, V);
         }
         // The store may have dependencies to unanalyzable loads and
         // stores.
         addChainDependencies(SU, Loads, UnknownValue);
         addChainDependencies(SU, Stores, UnknownValue);
       }
-    else { // SU is a load.
+    } else { // SU is a load.
       if (Objs.empty()) {
         // An unknown load depends on all stores.
         addChainDependencies(SU, Stores);
         addChainDependencies(SU, NonAliasStores);
 
         Loads.insert(SU, UnknownValue);
-        continue;
-      }
-
+      } else {
         for (auto &underlObj : Objs) {
           ValueType V = underlObj.getPointer();
           bool ThisMayAlias = underlObj.getInt();
 
           // Add precise dependencies against all previously seen stores
           // mapping to the same Value(s).
           addChainDependencies(SU, (ThisMayAlias ? Stores : NonAliasStores), V);
 
           // Map this load to V.
           (ThisMayAlias ? Loads : NonAliasLoads).insert(SU, V);
         }
         // The load may have dependencies to unanalyzable stores.
         addChainDependencies(SU, Stores, UnknownValue);
       }
+    }
 
     // Reduce maps if they grow huge.
     if (Stores.size() + Loads.size() >= HugeRegion) {
       DEBUG(dbgs() << "Reducing Stores and Loads maps.\n";);
       reduceHugeMemNodeMaps(Stores, Loads, ReductionSize);
     }
     if (NonAliasStores.size() + NonAliasLoads.size() >= HugeRegion) {
       DEBUG(dbgs() << "Reducing NonAliasStores and NonAliasLoads maps.\n";);