Constant integer vectors may also be negated.

llvm-svn: 51476

llvm/lib/Transforms/Scalar/InstructionCombining.cpp

@@ -550,6 +550,11 @@ static inline Value *dyn_castNegVal(Value *V) {
   // Constants can be considered to be negated values if they can be folded.
   if (ConstantInt *C = dyn_cast<ConstantInt>(V))
     return ConstantExpr::getNeg(C);
+
+  if (ConstantVector *C = dyn_cast<ConstantVector>(V))
+    if (C->getType()->getElementType()->isInteger())
+      return ConstantExpr::getNeg(C);
+
   return 0;
 }
 

llvm/test/Transforms/InstCombine/2008-05-22-NegValVector.ll

@@ -0,0 +1,8 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep sub
+
+define <3 x i8> @f(<3 x i8> %a) {
+  %A = sub <3 x i8> zeroinitializer, %a
+  %B = mul <3 x i8> %A, <i8 5, i8 5, i8 5>
+  ret <3 x i8> %B
+}
+