[SimpleLoopUnswitch] Verify LoopInfo in turnGuardIntoBranch under a flag

A follow-up for 64397d8. Only do verification if VerifyLoopInfo is
set.

Author: d-makogon

llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp

@@ -2735,7 +2735,8 @@ static BranchInst *turnGuardIntoBranch(IntrinsicInst *GI, Loop &L,
       MSSAU->getMemorySSA()->verifyMemorySSA();
   }
 
-  LI.verify(DT);
+  if (VerifyLoopInfo)
+    LI.verify(DT);
   ++NumGuards;
   return CheckBI;
 }

llvm/test/Transforms/SimpleLoopUnswitch/guards.ll

@@ -1,6 +1,6 @@
 ; RUN: opt -passes='loop(simple-loop-unswitch<nontrivial>),verify<loops>' -simple-loop-unswitch-guards -S < %s | FileCheck %s
 ; RUN: opt -passes='simple-loop-unswitch<nontrivial>' -simple-loop-unswitch-guards -S < %s | FileCheck %s
-; RUN: opt -passes='loop-mssa(simple-loop-unswitch<nontrivial>),verify<loops>' -simple-loop-unswitch-guards  -verify-memoryssa -S < %s | FileCheck %s
+; RUN: opt -passes='loop-mssa(simple-loop-unswitch<nontrivial>),verify<loops>' -simple-loop-unswitch-guards  -verify-memoryssa -verify-loop-info -S < %s | FileCheck %s
 
 ; XFAIL: *
 ; REQUIRES: asserts

llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-skip-selects-in-guards.ll

@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -passes='loop(simple-loop-unswitch<nontrivial>),verify<loops>' -S < %s | FileCheck %s
 ; RUN: opt -passes='loop-mssa(simple-loop-unswitch<nontrivial>),verify<loops>' -S < %s | FileCheck %s
-; RUN: opt -passes='simple-loop-unswitch<nontrivial>' -verify-memoryssa -S < %s | FileCheck %s
+; RUN: opt -passes='simple-loop-unswitch<nontrivial>' -verify-memoryssa -verify-loop-info -S < %s | FileCheck %s
 
 declare ptr @pluto()
 declare void @llvm.experimental.guard(i1, ...)