[InstCombine] rearrange code to remove repeated constant check; NFCI

llvm-svn: 315703
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index e12bff0..75cc683 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -950,13 +950,15 @@
   return nullptr;
 }
 
-static Instruction *foldAddWithConstant(BinaryOperator &Add,
-                                        InstCombiner::BuilderTy &Builder) {
+Instruction *InstCombiner::foldAddWithConstant(BinaryOperator &Add) {
   Value *Op0 = Add.getOperand(0), *Op1 = Add.getOperand(1);
   Constant *Op1C;
   if (!match(Op1, m_Constant(Op1C)))
     return nullptr;
 
+  if (Instruction *NV = foldOpWithConstantIntoOperand(Add))
+    return NV;
+
   Value *X;
   Type *Ty = Add.getType();
   if (match(Op0, m_ZExt(m_Value(X))) &&
@@ -1037,7 +1039,7 @@
   if (Value *V = SimplifyUsingDistributiveLaws(I))
     return replaceInstUsesWith(I, V);
 
-  if (Instruction *X = foldAddWithConstant(I, Builder))
+  if (Instruction *X = foldAddWithConstant(I))
     return X;
 
   // FIXME: This should be moved into the above helper function to allow these
@@ -1085,10 +1087,6 @@
     }
   }
 
-  if (isa<Constant>(RHS))
-    if (Instruction *NV = foldOpWithConstantIntoOperand(I))
-      return NV;
-
   if (I.getType()->isIntOrIntVectorTy(1))
     return BinaryOperator::CreateXor(LHS, RHS);