[LoopInfo] Add verification by recomputation.

Summary:
Current implementation of LI verifier isn't ideal and fails to detect
some cases when LI is incorrect. For instance, it checks that all
recorded loops are in a correct form, but it has no way to check if
there are no more other (unrecorded in LI) loops in the function. This
patch adds a way to detect such bugs.

Reviewers: chandlerc, sanjoy, hfinkel

Subscribers: llvm-commits, silvas, mzolotukhin

Differential Revision: https://reviews.llvm.org/D23437

llvm-svn: 280280

1 files changed, 6 insertions, 3 deletions

diff --git a/llvm/lib/Analysis/LoopInfo.cpp b/llvm/lib/Analysis/LoopInfo.cpp
index 9d2e38e19da..a5f816dd5ad 100644
--- a/llvm/lib/Analysis/LoopInfo.cpp
+++ b/llvm/lib/Analysis/LoopInfo.cpp
@@ -703,8 +703,10 @@ void LoopInfoWrapperPass::verifyAnalysis() const {
   // -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)
-    LI.verify();
+  if (VerifyLoopInfo) {
+    auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+    LI.verify(DT);
+  }
 }
 
 void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
@@ -719,7 +721,8 @@ void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const {
 PreservedAnalyses LoopVerifierPass::run(Function &F,
                                         FunctionAnalysisManager &AM) {
   LoopInfo &LI = AM.getResult<LoopAnalysis>(F);
-  LI.verify();
+  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
+  LI.verify(DT);
   return PreservedAnalyses::all();
 }