From 22c3caab6ee56e418b75e2321ad06e54f92a5221 Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Wed, 13 Feb 2008 22:06:36 +0000
Subject: [PATCH] While moving exit condition, do not drop loop latch on the
 floor.

llvm-svn: 47089
---
 llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp | 13 ++--
 .../LoopIndexSplit/2008-02-13-LoopLatch.ll    | 72 +++++++++++++++++++
 2 files changed, 81 insertions(+), 4 deletions(-)
 create mode 100644 llvm/test/Transforms/LoopIndexSplit/2008-02-13-LoopLatch.ll

diff --git a/llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp b/llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp
index 2d30eb6ff568..383415b228bf 100644
--- a/llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp
@@ -1579,17 +1579,22 @@ void LoopIndexSplit::moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
   // destination.
   BranchInst *ExitingBR = cast<BranchInst>(ExitingBB->getTerminator());
   ExitingBR->moveBefore(CurrentBR);
-  if (ExitingBR->getSuccessor(0) == ExitBB)
+  BasicBlock *OrigDestBB = NULL;
+  if (ExitingBR->getSuccessor(0) == ExitBB) {
+    OrigDestBB = ExitingBR->getSuccessor(1);
     ExitingBR->setSuccessor(1, ActiveBB);
-  else
+  }
+  else {
+    OrigDestBB = ExitingBR->getSuccessor(0);
     ExitingBR->setSuccessor(0, ActiveBB);
+  }
     
   // Remove split condition and current split condition branch.
   SC->eraseFromParent();
   CurrentBR->eraseFromParent();
 
-  // Connect exiting block to split condition block.
-  new BranchInst(CondBB, ExitingBB);
+  // Connect exiting block to original destination.
+  new BranchInst(OrigDestBB, ExitingBB);
 
   // Update PHINodes
   updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd);
diff --git a/llvm/test/Transforms/LoopIndexSplit/2008-02-13-LoopLatch.ll b/llvm/test/Transforms/LoopIndexSplit/2008-02-13-LoopLatch.ll
new file mode 100644
index 000000000000..0c67ea2c3070
--- /dev/null
+++ b/llvm/test/Transforms/LoopIndexSplit/2008-02-13-LoopLatch.ll
@@ -0,0 +1,72 @@
+; RUN: llvm-as < %s | opt -loop-index-split -disable-output
+; PR 2011
+	%struct.CLAUSE_HELP = type { i32, i32, i32, i32, i32*, i32, %struct.LIST_NODE*, %struct.LIST_NODE*, i32, i32, %struct.LITERAL_HELP**, i32, i32, i32, i32 }
+	%struct.LIST_NODE = type { %struct.LIST_NODE*, i8* }
+	%struct.LITERAL_HELP = type { i32, i32, i32, %struct.CLAUSE_HELP*, %struct.term* }
+	%struct.anon = type { %struct.LIST_NODE* }
+	%struct.st = type { %struct.subst*, %struct.LIST_NODE*, %struct.LIST_NODE*, i16, i16 }
+	%struct.subst = type { %struct.subst*, i32, %struct.term* }
+	%struct.term = type { i32, %struct.anon, %struct.LIST_NODE*, i32, i32 }
+
+define fastcc %struct.LIST_NODE* @inf_HyperResolvents(%struct.CLAUSE_HELP* %Clause, %struct.subst* %Subst, %struct.LIST_NODE* %Restlits, i32 %GlobalMaxVar, %struct.LIST_NODE* %FoundMap, i32 %StrictlyMaximal, { %struct.st*, [3001 x %struct.term*], [4000 x %struct.term*], i32 }* %Index, i32* %Flags, i32* %Precedence) nounwind  {
+entry:
+	br i1 false, label %bb960, label %bb885
+
+bb885:		; preds = %entry
+	ret %struct.LIST_NODE* null
+
+bb960:		; preds = %entry
+	br i1 false, label %bb1097, label %bb1005.preheader
+
+bb1005.preheader:		; preds = %bb960
+	ret %struct.LIST_NODE* null
+
+bb1097:		; preds = %bb960
+	br i1 false, label %bb1269.preheader, label %bb1141.preheader
+
+bb1141.preheader:		; preds = %bb1097
+	ret %struct.LIST_NODE* null
+
+bb1269.preheader:		; preds = %bb1097
+	br i1 false, label %bb1318, label %bb1281
+
+bb1281:		; preds = %bb1269.preheader
+	ret %struct.LIST_NODE* null
+
+bb1318:		; preds = %bb1269.preheader
+	br i1 false, label %bb1459, label %bb.nph52
+
+bb.nph52:		; preds = %bb1318
+	ret %struct.LIST_NODE* null
+
+bb1459:		; preds = %bb1318
+	br i1 false, label %bb1553, label %bb.nph62
+
+bb.nph62:		; preds = %bb1459
+	ret %struct.LIST_NODE* null
+
+bb1553:		; preds = %bb1669, %bb1459
+	%j295.0.reg2mem.0 = phi i32 [ %storemerge110, %bb1669 ], [ 0, %bb1459 ]		; <i32> [#uses=2]
+	br i1 false, label %bb1588, label %bb1616
+
+bb1588:		; preds = %bb1553
+	br label %bb1616
+
+bb1616:		; preds = %bb1588, %bb1553
+	%tmp1629 = icmp sgt i32 %j295.0.reg2mem.0, 0		; <i1> [#uses=1]
+	br i1 %tmp1629, label %bb1649, label %bb1632
+
+bb1632:		; preds = %bb1616
+	br label %bb1669
+
+bb1649:		; preds = %bb1616
+	br label %bb1669
+
+bb1669:		; preds = %bb1649, %bb1632
+	%storemerge110 = add i32 %j295.0.reg2mem.0, 1		; <i32> [#uses=2]
+	%tmp1672 = icmp sgt i32 %storemerge110, 0		; <i1> [#uses=1]
+	br i1 %tmp1672, label %bb1678, label %bb1553
+
+bb1678:		; preds = %bb1669
+	ret %struct.LIST_NODE* null
+}