From aa96ae780afa5475e62df284855a971216289212 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 17 Aug 2005 06:35:16 +0000
Subject: [PATCH] Use a new helper to split critical edges, making the code
 simpler.

Do not claim to not change the CFG.  We do change the cfg to split critical
edges.  This isn't causing us a problem now, but could likely do so in the
future.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22824 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/LoopStrengthReduce.cpp | 39 +++++++++++---------
 1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index e97e0911c17..c8e86d8e9d5 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -119,7 +119,15 @@ namespace {
     }
 
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
-      AU.setPreservesCFG();
+      // We split critical edges, so we change the CFG.  However, we do update
+      // many analyses if they are around.
+      AU.addPreservedID(LoopSimplifyID);
+      AU.addPreserved<LoopInfo>();
+      AU.addPreserved<DominatorSet>();
+      AU.addPreserved<ImmediateDominators>();
+      AU.addPreserved<DominanceFrontier>();
+      AU.addPreserved<DominatorTree>();
+
       AU.addRequiredID(LoopSimplifyID);
       AU.addRequired<LoopInfo>();
       AU.addRequired<DominatorSet>();
@@ -440,25 +448,20 @@ void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
       // code on all predecessor/successor paths.
       if (e != 1 &&
           PN->getIncomingBlock(i)->getTerminator()->getNumSuccessors() > 1) {
-        TerminatorInst *PredTI = PN->getIncomingBlock(i)->getTerminator();
-        for (unsigned Succ = 0; ; ++Succ) {
-          assert(Succ != PredTI->getNumSuccessors() &&"Didn't find successor?");
-          if (PredTI->getSuccessor(Succ) == PN->getParent()) {
-            // First step, split the critical edge.
-            SplitCriticalEdge(PredTI, Succ, P);
+
+        // First step, split the critical edge.
+        SplitCriticalEdge(PN->getIncomingBlock(i), PN->getParent(), P);
             
-            // Next step: move the basic block.  In particular, if the PHI node
-            // is outside of the loop, and PredTI is in the loop, we want to
-            // move the block to be immediately before the PHI block, not
-            // immediately after PredTI.
-            if (L->contains(PredTI->getParent()) &&
-                !L->contains(PN->getParent())) {
-              BasicBlock *NewBB = PN->getIncomingBlock(i);
-              NewBB->moveBefore(PN->getParent());
-            }
-            break;
-          }
+        // Next step: move the basic block.  In particular, if the PHI node
+        // is outside of the loop, and PredTI is in the loop, we want to
+        // move the block to be immediately before the PHI block, not
+        // immediately after PredTI.
+        if (L->contains(PN->getIncomingBlock(i)) &&
+            !L->contains(PN->getParent())) {
+          BasicBlock *NewBB = PN->getIncomingBlock(i);
+          NewBB->moveBefore(PN->getParent());
         }
+        break;
       }
 
       Value *&Code = InsertedCode[PN->getIncomingBlock(i)];
-- 
2.34.1