[wasm] Infrastructure to support loop exits in wasm

Changes:
- Add LoopExit and LoopExitValue functions in wasm-compiler.
- Handle kLoopExitValue opcode in simd-scalar-lowering.

Bug: v8:11298
Change-Id: I4d00402ed1913f927bec973b3d480ddc1990962b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2611251
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72030}

src/compiler/simd-scalar-lowering.cc

@@ -1577,6 +1577,19 @@ void SimdScalarLowering::LowerNode(Node* node) {
       }
       break;
     }
+    case IrOpcode::kLoopExitValue: {
+      if (!HasReplacement(0, node->InputAt(0))) break;
+      Node* control = node->InputAt(NodeProperties::FirstControlIndex(node));
+      Node** inputs = GetReplacementsWithType(node->InputAt(0), rep_type);
+      Node** rep_nodes = zone()->NewArray<Node*>(num_lanes);
+      for (int i = 0; i < num_lanes; i++) {
+        auto op =
+            common()->LoopExitValue(MachineTypeFrom(rep_type).representation());
+        rep_nodes[i] = graph()->NewNode(op, inputs[i], control);
+      }
+      ReplaceNode(node, rep_nodes, num_lanes);
+      break;
+    }
     case IrOpcode::kI64x2Add: {
       LowerBinaryOp(node, rep_type, machine()->Int64Add());
       break;

src/compiler/wasm-compiler.cc

@@ -403,6 +403,23 @@ Node* WasmGraphBuilder::TerminateLoop(Node* effect, Node* control) {
   return terminate;
 }
 
+Node* WasmGraphBuilder::LoopExit(Node* loop_node) {
+  DCHECK(loop_node->opcode() == IrOpcode::kLoop);
+  Node* loop_exit =
+      graph()->NewNode(mcgraph()->common()->LoopExit(), control(), loop_node);
+  Node* loop_exit_effect = graph()->NewNode(
+      mcgraph()->common()->LoopExitEffect(), effect(), loop_exit);
+  SetEffectControl(loop_exit_effect, loop_exit);
+  return loop_exit;
+}
+
+Node* WasmGraphBuilder::LoopExitValue(Node* value,
+                                      MachineRepresentation representation) {
+  DCHECK(control()->opcode() == IrOpcode::kLoopExit);
+  return graph()->NewNode(mcgraph()->common()->LoopExitValue(representation),
+                          value, control());
+}
+
 Node* WasmGraphBuilder::TerminateThrow(Node* effect, Node* control) {
   Node* terminate =
       graph()->NewNode(mcgraph()->common()->Throw(), effect, control);

src/compiler/wasm-compiler.h

@@ -196,6 +196,9 @@ class WasmGraphBuilder {
   Node* Param(unsigned index);
   Node* Loop(Node* entry);
   Node* TerminateLoop(Node* effect, Node* control);
+  Node* LoopExit(Node* loop_node);
+  // Assumes current control() is the corresponding loop exit.
+  Node* LoopExitValue(Node* value, MachineRepresentation representation);
   Node* TerminateThrow(Node* effect, Node* control);
   Node* Merge(unsigned count, Node** controls);
   Node* Phi(wasm::ValueType type, unsigned count, Node** vals_and_control);