From d0499af703db08b1c0c34d3c3722b06c1ae9583d Mon Sep 17 00:00:00 2001
From: Lauro Ramos Venancio <lauro.venancio@gmail.com>
Date: Wed, 6 Jun 2007 17:08:48 +0000
Subject: [PATCH] Fix PR1499.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37472 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/InstructionCombining.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 2a227423b60..01fcfabeba4 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -1346,6 +1346,10 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
       
       // Signed shift right.
       APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
+      // If any of the "high bits" are demanded, we should set the sign bit as
+      // demanded.
+      if (DemandedMask.countLeadingZeros() <= ShiftAmt)
+        DemandedMaskIn.set(BitWidth-1);
       if (SimplifyDemandedBits(I->getOperand(0),
                                DemandedMaskIn,
                                RHSKnownZero, RHSKnownOne, Depth+1))