[wasm][turbofan] Impose single appearance of each parameter

The register allocator sometimes fails if a parameter node appears
twice. This seems to be an issue in the register allocator rather than
a global assumption of Turbofan. This CL ensures duplication does not
happen in wasm code until the issue is resolved.

Changes:
- Cache parameter nodes in wasm-compiler.
- Use Dead() over Parameter() as placeholder in lowering stages.

Change-Id: I7afb5de45dd169819309fea3d3c1a7cfe68af62c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2756529
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73427}

src/compiler/int64-lowering.cc

@@ -35,8 +35,7 @@ Int64Lowering::Int64Lowering(
       stack_(zone),
       replacements_(nullptr),
       signature_(signature),
-      placeholder_(
-          graph->NewNode(common->Parameter(-2, "placeholder"), graph->start())),
+      placeholder_(graph->NewNode(common->Dead())),
       special_case_(std::move(special_case)) {
   DCHECK_NOT_NULL(graph);
   DCHECK_NOT_NULL(graph->end());

src/compiler/simd-scalar-lowering.cc

@@ -68,8 +68,7 @@ SimdScalarLowering::SimdScalarLowering(
       stack_(mcgraph_->zone()),
       replacements_(nullptr),
       signature_(signature),
-      placeholder_(graph()->NewNode(common()->Parameter(-2, "placeholder"),
-                                    graph()->start())),
+      placeholder_(graph()->NewNode(common()->Dead())),
       parameter_count_after_lowering_(-1) {
   DCHECK_NOT_NULL(graph());
   DCHECK_NOT_NULL(graph()->end());

src/compiler/wasm-compiler.cc

@@ -468,11 +468,24 @@ WasmGraphBuilder::~WasmGraphBuilder() = default;
 Node* WasmGraphBuilder::Start(unsigned params) {
   Node* start = graph()->NewNode(mcgraph()->common()->Start(params));
   graph()->SetStart(start);
+  parameters_ = zone_->NewArray<Node*>(params);
+  for (unsigned i = 0; i < params; i++) {
+    parameters_[i] = nullptr;
+  }
   return start;
 }
 
-Node* WasmGraphBuilder::Param(unsigned index) {
-  return gasm_->Parameter(index);
+Node* WasmGraphBuilder::Param(int index, const char* debug_name) {
+  DCHECK_NOT_NULL(graph()->start());
+  // Turbofan allows negative parameter indices.
+  static constexpr int kMinParameterIndex = -1;
+  DCHECK_GE(index, kMinParameterIndex);
+  int array_index = index - kMinParameterIndex;
+  if (parameters_[array_index] == nullptr) {
+    parameters_[array_index] = graph()->NewNode(
+        mcgraph()->common()->Parameter(index, debug_name), graph()->start());
+  }
+  return parameters_[array_index];
 }
 
 Node* WasmGraphBuilder::Loop(Node* entry) {
@@ -6678,20 +6691,9 @@ class WasmWrapperGraphBuilder : public WasmGraphBuilder {
     SetEffectControl(Start(wasm_param_count + 5));
 
     // Create the js_closure and js_context parameters.
-    Node* js_closure =
-        graph()->NewNode(mcgraph()->common()->Parameter(
-                             Linkage::kJSCallClosureParamIndex, "%closure"),
-                         graph()->start());
-    Node* js_context = graph()->NewNode(
-        mcgraph()->common()->Parameter(
-            Linkage::GetJSCallContextParamIndex(wasm_param_count + 1),
-            "%context"),
-        graph()->start());
-
-    // Create the instance_node node to pass as parameter. It is loaded from
-    // an actual reference to an instance or a placeholder reference,
-    // called {WasmExportedFunction} via the {WasmExportedFunctionData}
-    // structure.
+    Node* js_closure = Param(Linkage::kJSCallClosureParamIndex, "%closure");
+    Node* js_context = Param(
+        Linkage::GetJSCallContextParamIndex(wasm_param_count + 1), "%context");
     Node* function_data = gasm_->LoadFunctionDataFromJSFunction(js_closure);
     instance_node_.set(gasm_->LoadExportedFunctionInstance(function_data));
 

src/compiler/wasm-compiler.h

@@ -229,7 +229,7 @@ class WasmGraphBuilder {
   // Operations independent of {control} or {effect}.
   //-----------------------------------------------------------------------
   Node* Start(unsigned params);
-  Node* Param(unsigned index);
+  Node* Param(int index, const char* debug_name = nullptr);
   Node* Loop(Node* entry);
   Node* TerminateLoop(Node* effect, Node* control);
   Node* LoopExit(Node* loop_node);
@@ -727,6 +727,8 @@ class WasmGraphBuilder {
   MachineGraph* const mcgraph_;
   wasm::CompilationEnv* const env_;
 
+  Node** parameters_;
+
   WasmInstanceCacheNodes* instance_cache_ = nullptr;
 
   SetOncePointer<Node> instance_node_;