[Interpreter] Introduce IncStub and DecStub.

src/compiler/bytecode-graph-builder.cc

Index: src/compiler/bytecode-graph-builder.cc
diff --git a/src/compiler/bytecode-graph-builder.cc b/src/compiler/bytecode-graph-builder.cc
index 2249cbcb3f52d9e1be32458f305ab5d89b92ffdd..dd0a8204f5b11ea4648801ea494b320a89a3b549 100644
--- a/src/compiler/bytecode-graph-builder.cc
+++ b/src/compiler/bytecode-graph-builder.cc
@@ -1121,9 +1121,11 @@ void BytecodeGraphBuilder::VisitShiftRightLogical() {
 
 void BytecodeGraphBuilder::VisitInc() {
   FrameStateBeforeAndAfter states(this);
-  const Operator* js_op = javascript()->Add(BinaryOperationHints::Any());
+  // Note: Use subtract -1 here instead of add 1 to ensure we always convert to
+  // a number, not a string.
+  const Operator* js_op = javascript()->Subtract(BinaryOperationHints::Any());
   Node* node = NewNode(js_op, environment()->LookupAccumulator(),
-                       jsgraph()->OneConstant());
+                       jsgraph()->Constant(-1.0));
   environment()->BindAccumulator(node, &states);
 }