Move the dominator verification code out of special code embedded within
the PassManager code into a regular verifyAnalysis method.

Also, reorganize loop verification. Make the LoopPass infrastructure
call verifyLoop as needed instead of having LoopInfo::verifyAnalysis
check every loop in the function after each looop pass. Add a new
command-line argument, -verify-loop-info, to enable the expensive
full checking.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82952 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp
index 665e53d..ce2d29f 100644
--- a/lib/Analysis/LoopInfo.cpp
+++ b/lib/Analysis/LoopInfo.cpp
@@ -20,11 +20,22 @@
 #include "llvm/Analysis/Dominators.h"
 #include "llvm/Assembly/Writer.h"
 #include "llvm/Support/CFG.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include <algorithm>
 using namespace llvm;
 
+// Always verify loopinfo if expensive checking is enabled.
+#ifdef XDEBUG
+bool VerifyLoopInfo = true;
+#else
+bool VerifyLoopInfo = false;
+#endif
+static cl::opt<bool,true>
+VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
+                cl::desc("Verify loop info (time consuming)"));
+
 char LoopInfo::ID = 0;
 static RegisterPass<LoopInfo>
 X("loops", "Natural Loop Information", true, true);
@@ -375,10 +386,20 @@
 }
 
 void LoopInfo::verifyAnalysis() const {
+  // LoopInfo is a FunctionPass, but verifying every loop in the function
+  // each time verifyAnalysis is called is very expensive. The
+  // -verify-loop-info option can enable this. In order to perform some
+  // checking by default, LoopPass has been taught to call verifyLoop
+  // manually during loop pass sequences.
+
+  if (!VerifyLoopInfo) return;
+
   for (iterator I = begin(), E = end(); I != E; ++I) {
     assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
     (*I)->verifyLoopNest();
   }
+
+  // TODO: check BBMap consistency.
 }
 
 void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
diff --git a/lib/Analysis/LoopPass.cpp b/lib/Analysis/LoopPass.cpp
index e297ab4..22466ae 100644
--- a/lib/Analysis/LoopPass.cpp
+++ b/lib/Analysis/LoopPass.cpp
@@ -242,16 +242,24 @@
         dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, "");
       dumpPreservedSet(P);
 
-      if (!skipThisLoop)
+      if (!skipThisLoop) {
+        // Manually check that this loop is still healthy. This is done
+        // instead of relying on LoopInfo::verifyLoop since LoopInfo
+        // is a function pass and it's really expensive to verify every
+        // loop in the function every time. That level of checking can be
+        // enabled with the -verify-loop-info option.
+        Timer *T = StartPassTimer(LI);
+        CurrentLoop->verifyLoop();
+        StopPassTimer(LI, T);
+
+        // Then call the regular verifyAnalysis functions.
         verifyPreservedAnalysis(LP);
+      }
 
       removeNotPreservedAnalysis(P);
       recordAvailableAnalysis(P);
       removeDeadPasses(P, "", ON_LOOP_MSG);
 
-      // If dominator information is available then verify the info if requested.
-      verifyDomInfo(*LP, F);
-
       if (skipThisLoop)
         // Do not run other passes on this loop.
         break;