From 734d68c70ed942c3b5757358646c634f3bae39bc Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Fri, 28 Oct 2016 14:07:44 +0000
Subject: [PATCH] [SelectionDAG] computeKnownBits - early-out if any
 BUILD_VECTOR element has no known bits

No need to check the remaining elements - no common known bits are available.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285399 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index e6b8d2f5ade..db6accfb628 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2042,6 +2042,10 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
       // TODO: support per-element known bits.
       KnownOne &= KnownOne2;
       KnownZero &= KnownZero2;
+
+      // If we don't know any bits, early out.
+      if (!KnownOne && !KnownZero)
+        break;
     }
     break;
   case ISD::AND:
-- 
2.40.0