Long compile time with Release build and Polly

[ssijaric]

Summary

We came across a case where compiling one file (of many) in a customer application took 1m24s with a Release build vs 10s with a Release+Asserts build. The problem is that RegionBase<Tr>::getNameStr() is very expensive when the region's entry or exit block doesn't have a name, which is the case in the Release build as clang doesn't preserve names. The main use of RegionBase<Tr>::getNameStr() is to generate the message string when calling dumpPassInfo. This fix just adds the check that we are actually generating debug pass information, and thus avoids the call to RegionBase<Tr>::getNameStr() otherwise. With this change, the compile time for a Release only build goes down to 8s.

The long compile time will still be present when -debug-pass flag is used in a Release build. If that should also be fixed, perhaps we can just create an empty string upfront if NDEBUG is set and the region's entry or exit block doesn't have a name.

[ssijaric]

Created D8076, with llvm-commmits as subscribers this time.

lib/Analysis/RegionPass.cpp

     for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
       RegionPass *P = (RegionPass*)getContainedPass(Index);
 
-      dumpPassInfo(P, EXECUTION_MSG, ON_REGION_MSG,
-                   CurrentRegion->getNameStr());
-      dumpRequiredSet(P);
+      if (isPassDebuggingExecutionsOrMore()) {
+        dumpPassInfo(P, EXECUTION_MSG, ON_REGION_MSG,
+                     CurrentRegion->getNameStr());
+        dumpRequiredSet(P);
+      }
 
       initializeAnalysisImpl(P);
 

         Changed |= P->runOnRegion(CurrentRegion, *this);
       }
 
-      if (Changed)
-        dumpPassInfo(P, MODIFICATION_MSG, ON_REGION_MSG,
-                     skipThisRegion ? "<deleted>" :
-                                    CurrentRegion->getNameStr());
-      dumpPreservedSet(P);
+      if (isPassDebuggingExecutionsOrMore()) {
+        if (Changed)
+          dumpPassInfo(P, MODIFICATION_MSG, ON_REGION_MSG,
+                       skipThisRegion ? "<deleted>" :
+                                      CurrentRegion->getNameStr());
+        dumpPreservedSet(P);
+      }
 
       if (!skipThisRegion) {
         // Manually check that this region is still healthy. This is done

       removeNotPreservedAnalysis(P);
       recordAvailableAnalysis(P);
       removeDeadPasses(P,
-                       skipThisRegion ? "<deleted>" :
-                                      CurrentRegion->getNameStr(),
+                       (!isPassDebuggingExecutionsOrMore() || skipThisRegion) ?
+                       "<deleted>" :  CurrentRegion->getNameStr(),
                        ON_REGION_MSG);
 
       if (skipThisRegion)