[turbofan] Simplify lowering of number addition.

src/compiler/simplified-lowering.cc

Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc b/src/compiler/simplified-lowering.cc
index cd434a470c36bc7618e2bcede456dde255d25a4d..b335389729ae8daabf6e5d6082874edcd6e51c2a 100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -739,20 +739,10 @@ class RepresentationSelector {
       case IrOpcode::kNumberSubtract: {
         // Add and subtract reduce to Int32Add/Sub if the inputs
         // are already integers and all uses are truncating.
-        if (CanLowerToInt32Binop(node, use)) {
+        if (CanLowerToWord32AdditiveBinop(node, use)) {
           // => signed Int32Add/Sub
           VisitInt32Binop(node);
           if (lower()) NodeProperties::ChangeOp(node, Int32Op(node));
-        } else if (CanLowerToUint32Binop(node, use)) {
-          // => unsigned Int32Add/Sub
-          VisitUint32Binop(node);
-          if (lower()) NodeProperties::ChangeOp(node, Uint32Op(node));
-        } else if (CanLowerToWord32AdditiveBinop(node, use)) {
-          // => signed Int32Add/Sub, truncating inputs
-          ProcessTruncateWord32Input(node, 0);
-          ProcessTruncateWord32Input(node, 1);
-          SetOutput(node, kMachInt32);
-          if (lower()) NodeProperties::ChangeOp(node, Int32Op(node));
         } else {
           // => Float64Add/Sub
           VisitFloat64Binop(node);