[SeparateConstOffsetFromGEP] Fixed a bug in rebuilding OR expressions

The two operands of the new OR expression should be NextInChain and TheOther
instead of the two original operands.

Added a regression test in split-gep.ll.

Hao Liu reported this bug, and provded the test case and an initial patch.
Thanks! 

llvm-svn: 220615

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp b/llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
index 6557ce4575d..449198c1d2f 100644
--- a/llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
+++ b/llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
@@ -519,8 +519,13 @@ Value *ConstantOffsetExtractor::removeConstOffset(unsigned ChainIndex) {
     //
     // Replacing the "or" with "add" is fine, because
     //   a | (b + 5) = a + (b + 5) = (a + b) + 5
-    return BinaryOperator::CreateAdd(BO->getOperand(0), BO->getOperand(1),
-                                     BO->getName(), IP);
+    if (OpNo == 0) {
+      return BinaryOperator::CreateAdd(NextInChain, TheOther, BO->getName(),
+                                       IP);
+    } else {
+      return BinaryOperator::CreateAdd(TheOther, NextInChain, BO->getName(),
+                                       IP);
+    }
   }
 
   // We can reuse BO in this case, because the new expression shares the same