From 06d4033a354115904e9df23608f9a7cd543d5dbc Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Mon, 26 Oct 2009 22:18:58 +0000
Subject: [PATCH] Simplify this code. LoopDeletion doesn't need to explicit
 check that the loop exiting block dominates the latch block; if
 ScalarEvolution can prove that the trip-count is finite, that's sufficient.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85165 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/LoopDeletion.cpp | 26 ++------------------------
 1 file changed, 2 insertions(+), 24 deletions(-)

diff --git a/lib/Transforms/Scalar/LoopDeletion.cpp b/lib/Transforms/Scalar/LoopDeletion.cpp
index 8133a06f3f8..3fb6c916f19 100644
--- a/lib/Transforms/Scalar/LoopDeletion.cpp
+++ b/lib/Transforms/Scalar/LoopDeletion.cpp
@@ -33,8 +33,6 @@ namespace {
     // Possibly eliminate loop L if it is dead.
     bool runOnLoop(Loop* L, LPPassManager& LPM);
     
-    bool SingleDominatingExit(Loop* L,
-                              SmallVector<BasicBlock*, 4>& exitingBlocks);
     bool IsLoopDead(Loop* L, SmallVector<BasicBlock*, 4>& exitingBlocks,
                     SmallVector<BasicBlock*, 4>& exitBlocks,
                     bool &Changed, BasicBlock *Preheader);
@@ -63,25 +61,6 @@ Pass* llvm::createLoopDeletionPass() {
   return new LoopDeletion();
 }
 
-/// SingleDominatingExit - Checks that there is only a single blocks that 
-/// branches out of the loop, and that it also g the latch block.  Loops
-/// with multiple or non-latch-dominating exiting blocks could be dead, but we'd
-/// have to do more extensive analysis to make sure, for instance, that the 
-/// control flow logic involved was or could be made loop-invariant.
-bool LoopDeletion::SingleDominatingExit(Loop* L,
-                                   SmallVector<BasicBlock*, 4>& exitingBlocks) {
-  
-  if (exitingBlocks.size() != 1)
-    return false;
-  
-  BasicBlock* latch = L->getLoopLatch();
-  if (!latch)
-    return false;
-  
-  DominatorTree& DT = getAnalysis<DominatorTree>();
-  return DT.dominates(exitingBlocks[0], latch);
-}
-
 /// IsLoopDead - Determined if a loop is dead.  This assumes that we've already
 /// checked for unique exit and exiting blocks, and that the code is in LCSSA
 /// form.
@@ -154,9 +133,8 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
   if (exitBlocks.size() != 1)
     return false;
   
-  // Loops with multiple exits or exits that don't dominate the latch
-  // are too complicated to handle correctly.
-  if (!SingleDominatingExit(L, exitingBlocks))
+  // Loops with multiple exits are too complicated to handle correctly.
+  if (exitingBlocks.size() != 1)
     return false;
   
   // Finally, we have to check that the loop really is dead.