From 9e242e684e8810a89261b6165c33be0d83574fa8 Mon Sep 17 00:00:00 2001
From: Michael Zolotukhin <mzolotukhin@apple.com>
Date: Tue, 22 Sep 2015 00:22:47 +0000
Subject: [PATCH] [LoopUnswitch] Require DominatorTree info.

Summary:
We should either require the DT info to be available, or check if it's
available in every place we use DT (and we already miss such check in
one place, which causes failures in some cases). As other loop passes
preserve DT and it's usually available, it makes sense to just require
it here.

There is no regression test, because the bug only shows up if pass
manager decides to clean DT info right before LoopUnswitch. If
loop-unswitch is run separately, DT is available, so bug isn't exposed.

Reviewers: chandlerc, hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13036

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248230 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/LoopUnswitch.cpp | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/lib/Transforms/Scalar/LoopUnswitch.cpp b/lib/Transforms/Scalar/LoopUnswitch.cpp
index a00603bd22f..abd8994023d 100644
--- a/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -193,6 +193,7 @@ namespace {
       AU.addPreserved<LoopInfoWrapperPass>();
       AU.addRequiredID(LCSSAID);
       AU.addPreservedID(LCSSAID);
+      AU.addRequired<DominatorTreeWrapperPass>();
       AU.addPreserved<DominatorTreeWrapperPass>();
       AU.addPreserved<ScalarEvolutionWrapperPass>();
       AU.addRequired<TargetTransformInfoWrapperPass>();
@@ -412,23 +413,19 @@ bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) {
       *L->getHeader()->getParent());
   LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
   LPM = &LPM_Ref;
-  DominatorTreeWrapperPass *DTWP =
-      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
-  DT = DTWP ? &DTWP->getDomTree() : nullptr;
+  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
   currentLoop = L;
   Function *F = currentLoop->getHeader()->getParent();
   bool Changed = false;
   do {
-    assert(!DT || currentLoop->isLCSSAForm(*DT));
+    assert(currentLoop->isLCSSAForm(*DT));
     redoLoop = false;
     Changed |= processCurrentLoop();
   } while(redoLoop);
 
-  if (Changed) {
-    // FIXME: Reconstruct dom info, because it is not preserved properly.
-    if (DT)
-      DT->recalculate(*F);
-  }
+  // FIXME: Reconstruct dom info, because it is not preserved properly.
+  if (Changed)
+    DT->recalculate(*F);
   return Changed;
 }
 
@@ -1196,8 +1193,7 @@ void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
     // domtree here -- instead we force it to do a full recomputation
     // after the pass is complete -- but we do need to inform it of
     // new blocks.
-    if (DT)
-      DT->addNewBlock(Abort, NewSISucc);
+    DT->addNewBlock(Abort, NewSISucc);
   }
 
   SimplifyCode(Worklist, L);
-- 
2.34.1