Actually, disable this code for now. More analysis and improvements to

the X86 backend are needed before this should be enabled by default.

llvm-svn: 44657

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 918db383530..ba3c0ac33dc 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2134,6 +2134,12 @@ SDOperand DAGCombiner::visitXOR(SDNode *N) {
 /// visitShiftByConstant - Handle transforms common to the three shifts, when
 /// the shift amount is a constant.
 SDOperand DAGCombiner::visitShiftByConstant(SDNode *N, unsigned Amt) {
+  // FIXME: disable this for now.  This pessimizes some common cases like:
+  //
+  //void foo(int *X, int i) { X[i & 1235] = 1; }
+  //int bar(int *X, int i) { return X[i & 255]; }
+  return SDOperand();
+  
   SDNode *LHS = N->getOperand(0).Val;
   if (!LHS->hasOneUse()) return SDOperand();