From 60a12907c309fa6e0ae465ffffef1ca3af8d7992 Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Mon, 24 Mar 2008 20:16:14 +0000
Subject: [PATCH] Add incoming value from header only if phi node has any use
 inside the loop.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48738 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/LoopIndexSplit.cpp      |  5 +-
 .../LoopIndexSplit/2008-03-24-ExitPhi.ll      | 69 +++++++++++++++++++
 2 files changed, 72 insertions(+), 2 deletions(-)
 create mode 100644 test/Transforms/LoopIndexSplit/2008-03-24-ExitPhi.ll

diff --git a/lib/Transforms/Scalar/LoopIndexSplit.cpp b/lib/Transforms/Scalar/LoopIndexSplit.cpp
index 3aedb93fd17..513cad8a566 100644
--- a/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ b/lib/Transforms/Scalar/LoopIndexSplit.cpp
@@ -1665,8 +1665,9 @@ void LoopIndexSplit::updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch,
             break;
           }
 
-      assert (NewV && "Unable to find new incoming value for exit block PHI");
-      PN->addIncoming(NewV, Header);
+      // Add incoming value from header only if PN has any use inside the loop.
+      if (NewV)
+        PN->addIncoming(NewV, Header);
 
     } else if (Instruction *PHI = dyn_cast<Instruction>(V)) {
       // If this instruction is IVIncrement then IV is new incoming value 
diff --git a/test/Transforms/LoopIndexSplit/2008-03-24-ExitPhi.ll b/test/Transforms/LoopIndexSplit/2008-03-24-ExitPhi.ll
new file mode 100644
index 00000000000..24f22cab4ea
--- /dev/null
+++ b/test/Transforms/LoopIndexSplit/2008-03-24-ExitPhi.ll
@@ -0,0 +1,69 @@
+; RUN: llvm-as < %s | opt -loop-index-split -disable-output
+; Handle Exit block phis that do not have any use inside the loop.
+
+	%struct.ATOM = type { double, double, double, double, double, double, i32, double, double, double, double, i8*, i8, [9 x i8], double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, double, [200 x i8*], [32 x i8*], [32 x i8], i32 }
+	%struct.FILE = type { i8*, i32, i32, i16, i16, %struct.__sbuf, i32, i8*, i32 (i8*)*, i32 (i8*, i8*, i32)*, i64 (i8*, i64, i32)*, i32 (i8*, i8*, i32)*, %struct.__sbuf, %struct.__sFILEX*, i32, [3 x i8], [1 x i8], %struct.__sbuf, i32, i64 }
+	%struct.__sFILEX = type opaque
+	%struct.__sbuf = type { i8*, i32 }
+
+define i32 @math([80 x i8]* %tokens, double* %fvalue, i32* %ivalue, %struct.FILE* %ip, %struct.FILE* %op, i32 %echo) nounwind  {
+entry:
+	br i1 false, label %bb.i, label %bb35.i
+bb.i:		; preds = %entry
+	br i1 false, label %bb6.i, label %bb9.i
+bb9.i:		; preds = %bb.i
+	ret i32 0
+bb35.i:		; preds = %entry
+	ret i32 0
+bb6.i:		; preds = %bb.i
+	br i1 false, label %a_l2_f.exit, label %bb16.i
+bb16.i:		; preds = %bb6.i
+	ret i32 0
+a_l2_f.exit:		; preds = %bb6.i
+	br i1 false, label %bb7.i97, label %bb6.i71
+bb6.i71:		; preds = %a_l2_f.exit
+	ret i32 0
+bb7.i97:		; preds = %a_l2_f.exit
+	br i1 false, label %bb, label %bb18.i102
+bb18.i102:		; preds = %bb7.i97
+	ret i32 0
+bb:		; preds = %bb7.i97
+	br i1 false, label %bb38, label %AFOUND
+bb38:		; preds = %bb
+	br i1 false, label %bb111, label %bb7.i120
+AFOUND:		; preds = %bb
+	ret i32 0
+bb7.i120:		; preds = %bb38
+	ret i32 0
+bb111:		; preds = %bb38
+	switch i32 0, label %bb574 [
+		 i32 1, label %bb158
+		 i32 0, label %bb166
+	]
+bb158:		; preds = %bb111
+	ret i32 0
+bb166:		; preds = %bb111
+	ret i32 0
+bb574:		; preds = %bb111
+	br i1 false, label %bb11.i249, label %bb600
+bb11.i249:		; preds = %bb574
+	br i1 false, label %bb11.i265, label %bb596
+bb11.i265:		; preds = %bb590, %bb11.i249
+	%i.1.reg2mem.0 = phi i32 [ %tmp589.reg2mem.0, %bb590 ], [ 0, %bb11.i249 ]		; <i32> [#uses=2]
+	%tmp13.i264 = icmp slt i32 %i.1.reg2mem.0, 1		; <i1> [#uses=1]
+	br i1 %tmp13.i264, label %bb16.i267, label %bb30.i279
+bb16.i267:		; preds = %bb11.i265
+	br label %bb590
+bb30.i279:		; preds = %bb11.i265
+	br label %bb590
+bb590:		; preds = %bb30.i279, %bb16.i267
+	%tmp5876282.reg2mem.0 = phi %struct.ATOM* [ null, %bb30.i279 ], [ null, %bb16.i267 ]		; <%struct.ATOM*> [#uses=1]
+	%tmp589.reg2mem.0 = add i32 %i.1.reg2mem.0, 1		; <i32> [#uses=2]
+	%tmp593 = icmp slt i32 %tmp589.reg2mem.0, 0		; <i1> [#uses=1]
+	br i1 %tmp593, label %bb11.i265, label %bb596
+bb596:		; preds = %bb590, %bb11.i249
+	%ap.0.reg2mem.0 = phi %struct.ATOM* [ null, %bb11.i249 ], [ %tmp5876282.reg2mem.0, %bb590 ]		; <%struct.ATOM*> [#uses=0]
+	ret i32 0
+bb600:		; preds = %bb574
+	ret i32 0
+}