Teach InstCombine to optimize extract of a value from a vector add operation with a constant zero.

llvm-svn: 172576

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index dd7ea14e8a8..8bfcc805bc8 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -13,7 +13,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "InstCombine.h"
+#include "llvm/Support/PatternMatch.h"
 using namespace llvm;
+using namespace PatternMatch;
 
 /// CheapToScalarize - Return true if the value is cheaper to scalarize than it
 /// is to leave as a vector operation.  isConstant indicates whether we're
@@ -92,6 +94,13 @@ static Value *FindScalarElement(Value *V, unsigned EltNo) {
     return FindScalarElement(SVI->getOperand(1), InEl - LHSWidth);
   }
 
+  // Extract a value from a vector add operation with a constant zero.
+  Value *Val = 0; Constant *Con = 0;
+  if (match(V, m_Add(m_Value(Val), m_Constant(Con)))) {
+    if (Con->getAggregateElement(EltNo)->isNullValue())
+      return FindScalarElement(Val, EltNo);
+  }
+
   // Otherwise, we don't know.
   return 0;
 }