Optimize shift lefts of a constant by a value plus constant into a single shift.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174152 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineShifts.cpp b/lib/Transforms/InstCombine/InstCombineShifts.cpp
index 8cf76e5e8a..f9e94f225f 100644
--- a/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -709,6 +709,12 @@ Instruction *InstCombiner::visitShl(BinaryOperator &I) {
       match(I.getOperand(1), m_Constant(C2)))
     return BinaryOperator::CreateShl(ConstantExpr::getShl(C1, C2), A);
 
+  // shl (c1 , add(y , c2)) -> (shl (shl(c1, c2)), y)
+  if (match(I.getOperand(0), m_Constant(C1)) &&
+      match(I.getOperand(1), m_Add(m_Value(A), m_Constant(C2)))) {
+    return BinaryOperator::CreateShl(ConstantExpr::getShl(C1, C2), A);
+  }
+
   return 0;
 }