[gasm] Fix superfluous LoopExitValue node

Loop exits are marked automatically by the loop scope mechanism in
combination with MergeState. Creating a LoopExitValue node explicitly
created an invalid graph.

Drive-by: Remove LoopExit{,Effect,Value} convenience methods.

Bug: chromium:1044878,v8:9972
Change-Id: I6fb52a8463e5352b5a5b243f800a9eda47df9d5a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2016593
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65949}

src/compiler/graph-assembler.cc

@@ -632,20 +632,6 @@ Node* GraphAssembler::Checkpoint(FrameState frame_state) {
                                   control()));
 }
 
-Node* GraphAssembler::LoopExit(Control loop_header) {
-  return AddNode(
-      graph()->NewNode(common()->LoopExit(), control(), loop_header));
-}
-
-Node* GraphAssembler::LoopExitEffect() {
-  return AddNode(
-      graph()->NewNode(common()->LoopExitEffect(), effect(), control()));
-}
-
-Node* GraphAssembler::LoopExitValue(Node* value) {
-  return AddNode(graph()->NewNode(common()->LoopExitValue(), value, control()));
-}
-
 Node* GraphAssembler::DebugBreak() {
   return AddNode(
       graph()->NewNode(machine()->DebugBreak(), effect(), control()));

src/compiler/graph-assembler.h

@@ -307,9 +307,6 @@ class V8_EXPORT_PRIVATE GraphAssembler {
 
   Node* TypeGuard(Type type, Node* value);
   Node* Checkpoint(FrameState frame_state);
-  Node* LoopExit(Control loop_header);
-  Node* LoopExitEffect();
-  Node* LoopExitValue(Node* value);
 
   Node* Store(StoreRepresentation rep, Node* object, Node* offset, Node* value);
   Node* Load(MachineType type, Node* object, Node* offset);
@@ -547,10 +544,12 @@ void GraphAssembler::MergeState(GraphAssemblerLabel<sizeof...(Vars)>* label,
     DCHECK_NOT_NULL(*loop_headers_.back());
 
     // Mark this exit to enable loop peeling.
-    LoopExit(Control{*loop_headers_.back()});
-    LoopExitEffect();
+    AddNode(graph()->NewNode(common()->LoopExit(), control(),
+                             *loop_headers_.back()));
+    AddNode(graph()->NewNode(common()->LoopExitEffect(), effect(), control()));
     for (size_t i = 0; i < kVarCount; i++) {
-      var_array[i] = LoopExitValue(var_array[i]);
+      var_array[i] = AddNode(
+          graph()->NewNode(common()->LoopExitValue(), var_array[i], control()));
     }
   }
 

src/compiler/js-call-reducer.cc

@@ -544,8 +544,7 @@ class JSCallReducerAssembler : public JSGraphAssembler {
       }
 
       gasm_->Bind(&loop_exit);
-      return TNode<Object>::UncheckedCast(
-          gasm_->LoopExitValue(loop_exit.PhiAt<Object>(0)));
+      return TNode<Object>::UncheckedCast(loop_exit.PhiAt<Object>(0));
     }
 
     void ValueIsUnused() { USE(Value()); }