Teach codegen to handle:

 (X != null) | (Y != null) --> (X|Y) != 0
 (X == null) & (Y == null) --> (X|Y) == 0

so that instcombine can stop doing this for pointers.  This is part of PR3351,
which is a case where instcombine doing this for pointers (inserting ptrtoint)
is pessimizing code.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92406 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 74d624f364..40eb9eeb82 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1195,6 +1195,18 @@ SelectionDAGBuilder::ShouldEmitAsBranches(const std::vector<CaseBlock> &Cases){
     return false;
   }
 
+  // Handle: (X != null) | (Y != null) --> (X|Y) != 0
+  // Handle: (X == null) & (Y == null) --> (X|Y) == 0
+  if (Cases[0].CmpRHS == Cases[1].CmpRHS &&
+      Cases[0].CC == Cases[1].CC &&
+      isa<Constant>(Cases[0].CmpRHS) &&
+      cast<Constant>(Cases[0].CmpRHS)->isNullValue()) {
+    if (Cases[0].CC == ISD::SETEQ && Cases[0].TrueBB == Cases[1].ThisBB)
+      return false;
+    if (Cases[0].CC == ISD::SETNE && Cases[0].FalseBB == Cases[1].ThisBB)
+      return false;
+  }
+  
   return true;
 }