[wasm] Int64Lowering of Word64Popcnt.

src/compiler/int64-lowering.cc

Index: src/compiler/int64-lowering.cc
diff --git a/src/compiler/int64-lowering.cc b/src/compiler/int64-lowering.cc
index 1ef2e2140581afce1c2a9bb02b76d01fd368fffc..a6f355d4f5e90aadab205ed4af07623f3f7d5da2 100644
--- a/src/compiler/int64-lowering.cc
+++ b/src/compiler/int64-lowering.cc
@@ -447,6 +447,21 @@ void Int64Lowering::LowerNode(Node* node) {
 
     // kExprI64Clz:
     // kExprI64Ctz:
+    case IrOpcode::kWord64Popcnt: {
+      DCHECK(node->InputCount() == 1);
+      Node* input = node->InputAt(0);
+      // We assume that a Word64Popcnt node only has been created if
+      // Word32Popcnt is actually supported.
+      DCHECK(machine()->Word32Popcnt().IsSupported());
+      ReplaceNode(node, graph()->NewNode(
+                            machine()->Int32Add(),
+                            graph()->NewNode(machine()->Word32Popcnt().op(),
+                                             GetReplacementLow(input)),
+                            graph()->NewNode(machine()->Word32Popcnt().op(),
+                                             GetReplacementHigh(input))),
+                  graph()->NewNode(common()->Int32Constant(0)));
+      break;
+    }
     // kExprI64Popcnt:
 
     default: { DefaultLowering(node); }