From ee7bf41c06f3d760792487cbceef747a766e775a Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Mon, 19 May 2008 22:23:55 +0000
Subject: [PATCH] Do not erase induction variable increment if it is used
 outside the loop.

llvm-svn: 51280
---
 llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp | 24 +++++++++--
 .../LoopIndexSplit/2008-05-19-IndVar.ll       | 41 +++++++++++++++++++
 2 files changed, 61 insertions(+), 4 deletions(-)
 create mode 100644 llvm/test/Transforms/LoopIndexSplit/2008-05-19-IndVar.ll

diff --git a/llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp b/llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp
index 8b554444c526..5faec97a9711 100644
--- a/llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp
@@ -596,11 +596,27 @@ bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) {
     if (isa<PHINode>(I) || I == LTerminator)
       continue;
 
-    if (I == IndVarIncrement) 
-      I->replaceAllUsesWith(ExitValue);
-    else
+    if (I == IndVarIncrement) {
+      // Replace induction variable increment if it is not used outside 
+      // the loop.
+      bool UsedOutsideLoop = false;
+      for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 
+           UI != E; ++UI) {
+        if (Instruction *Use = dyn_cast<Instruction>(UI)) 
+          if (!L->contains(Use->getParent())) {
+            UsedOutsideLoop = true;
+            break;
+          }
+      }
+      if (!UsedOutsideLoop) {
+        I->replaceAllUsesWith(ExitValue);
+        I->eraseFromParent();
+      }
+    }
+    else {
       I->replaceAllUsesWith(UndefValue::get(I->getType()));
-    I->eraseFromParent();
+      I->eraseFromParent();
+    }
   }
 
   LPM->deleteLoopFromQueue(L);
diff --git a/llvm/test/Transforms/LoopIndexSplit/2008-05-19-IndVar.ll b/llvm/test/Transforms/LoopIndexSplit/2008-05-19-IndVar.ll
new file mode 100644
index 000000000000..8aa2e52b3fe9
--- /dev/null
+++ b/llvm/test/Transforms/LoopIndexSplit/2008-05-19-IndVar.ll
@@ -0,0 +1,41 @@
+; RUN: llvm-as < %s | opt -loop-index-split | llvm-dis | grep tmp8 | count 3
+; count 3 = increment + phi + store
+;PR2294
+@g_2 = external global i16		; <i16*> [#uses=4]
+@g_5 = external global i32		; <i32*> [#uses=1]
+@.str = external constant [4 x i8]		; <[4 x i8]*> [#uses=1]
+
+declare void @func_1() nounwind 
+
+define i32 @main() nounwind  {
+entry:
+	%tmp101.i = load i16* @g_2, align 2		; <i16> [#uses=1]
+	%tmp112.i = icmp sgt i16 %tmp101.i, 0		; <i1> [#uses=1]
+	br i1 %tmp112.i, label %bb.preheader.i, label %func_1.exit
+bb.preheader.i:		; preds = %entry
+	%g_2.promoted.i = load i16* @g_2		; <i16> [#uses=1]
+	br label %bb.i
+bb.i:		; preds = %bb6.i, %bb.preheader.i
+	%g_2.tmp.0.i = phi i16 [ %g_2.promoted.i, %bb.preheader.i ], [ %tmp8.i, %bb6.i ]		; <i16> [#uses=2]
+	%tmp2.i = icmp eq i16 %g_2.tmp.0.i, 0		; <i1> [#uses=1]
+	br i1 %tmp2.i, label %bb4.i, label %bb6.i
+bb4.i:		; preds = %bb.i
+	%tmp5.i = volatile load i32* @g_5, align 4		; <i32> [#uses=0]
+	br label %bb6.i
+bb6.i:		; preds = %bb4.i, %bb.i
+	%tmp8.i = add i16 %g_2.tmp.0.i, 1		; <i16> [#uses=3]
+	%tmp11.i = icmp sgt i16 %tmp8.i, 0		; <i1> [#uses=1]
+	br i1 %tmp11.i, label %bb.i, label %return.loopexit.i
+return.loopexit.i:		; preds = %bb6.i
+	%tmp8.i.lcssa = phi i16 [ %tmp8.i, %bb6.i ]		; <i16> [#uses=1]
+	store i16 %tmp8.i.lcssa, i16* @g_2
+	br label %func_1.exit
+func_1.exit:		; preds = %return.loopexit.i, %entry
+	%tmp1 = load i16* @g_2, align 2		; <i16> [#uses=1]
+	%tmp12 = sext i16 %tmp1 to i32		; <i32> [#uses=1]
+	%tmp3 = tail call i32 (i8*, ...)* @printf( i8* getelementptr ([4 x i8]* @.str, i32 0, i32 0), i32 %tmp12 ) nounwind 		; <i32> [#uses=0]
+	ret i32 0
+}
+
+declare i32 @printf(i8*, ...) nounwind 
+