[llvm] r285399 - [SelectionDAG] computeKnownBits - early-out if any BUILD_VECTOR element has no known bits

[Simon Pilgrim via llvm-commits]

Author: rksimon
Date: Fri Oct 28 09:07:44 2016
New Revision: 285399

URL: http://llvm.org/viewvc/llvm-project?rev=285399&view=rev
Log:
[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.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=285399&r1=285398&r2=285399&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Fri Oct 28 09:07:44 2016
@@ -2042,6 +2042,10 @@ void SelectionDAG::computeKnownBits(SDVa
       // 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: