[dart2js] Implement JS_EMBEDDED_GLOBAL as an instrution.

Usins an SSA instruction defers the generation of a 'modular
expression' until codegen, when other modular expressions are
generated. This allows JS_EMBEDDED_GLOBAL nodes to be duplicated.

Change-Id: I2fded6c85598e475ab61cbd67a449aae59ecb260
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/433460
Reviewed-by: Nate Biggs <[email protected]>
Commit-Queue: Stephen Adams <[email protected]>

Author: rakudrama

pkg/compiler/lib/src/ssa/builder.dart

@@ -5983,9 +5983,6 @@ class KernelSsaGraphBuilder extends ir.VisitorDefault<void>
       'JS_EMBEDDED_GLOBAL',
       'second ',
     )!;
-    js.Template expr = js.js.expressionTemplateYielding(
-      _emitter.generateEmbeddedGlobalAccess(globalName),
-    );
 
     NativeBehavior nativeBehavior = _elementMap
         .getNativeBehaviorForJsEmbeddedGlobalCall(invocation);
@@ -5995,12 +5992,8 @@ class KernelSsaGraphBuilder extends ir.VisitorDefault<void>
       closedWorld,
     );
     push(
-      HForeignCode(
-        expr,
-        ssaType,
-        const <HInstruction>[],
-        nativeBehavior: nativeBehavior,
-      )..sourceInformation = sourceInformation,
+      HEmbeddedGlobalGet(globalName, nativeBehavior, ssaType)
+        ..sourceInformation = sourceInformation,
     );
   }
 

pkg/compiler/lib/src/ssa/codegen.dart

@@ -2780,6 +2780,11 @@ class SsaCodeGenerator implements HVisitor<void>, HBlockInformationVisitor {
     registerForeignTypes(node);
   }
 
+  @override
+  void visitEmbeddedGlobalGet(HEmbeddedGlobalGet node) {
+    push(_emitter.generateEmbeddedGlobalAccess(node.name));
+  }
+
   @override
   void visitCreate(HCreate node) {
     js.Expression jsClassReference = _emitter.constructorAccess(node.element);

pkg/compiler/lib/src/ssa/nodes.dart

@@ -53,6 +53,7 @@ abstract class HVisitor<R> {
   R visitCreate(HCreate node);
   R visitCreateBox(HCreateBox node);
   R visitDivide(HDivide node);
+  R visitEmbeddedGlobalGet(HEmbeddedGlobalGet node);
   R visitExit(HExit node);
   R visitExitTry(HExitTry node);
   R visitFieldGet(HFieldGet node);
@@ -504,6 +505,8 @@ class HBaseVisitor<R> extends HGraphVisitor implements HVisitor<R> {
   @override
   R visitDivide(HDivide node) => visitBinaryArithmetic(node);
   @override
+  R visitEmbeddedGlobalGet(HEmbeddedGlobalGet node) => visitInstruction(node);
+  @override
   R visitExit(HExit node) => visitControlFlow(node);
   @override
   R visitExitTry(HExitTry node) => visitControlFlow(node);
@@ -1137,6 +1140,7 @@ enum _GvnType {
   charCodeAt,
   arrayFlagsGet,
   arrayFlagsCheck,
+  embeddedGlobal,
 }
 
 abstract class HInstruction implements SpannableWithEntity {
@@ -5114,3 +5118,41 @@ class HIsLateSentinel extends HInstruction {
   @override
   String toString() => 'HIsLateSentinel()';
 }
+
+/// Reads an 'embedded global' to access some kind of metadata or value produced
+/// by the compiler.
+///
+/// This instruction corresponds to the `JS_EMBEDDED_GLOBAL` top level method in
+/// `foreign_helper.dart`.  The [name] should be a constant defined in the
+/// `_embedded_names` or `_js_shared_embedded_names` library.
+class HEmbeddedGlobalGet extends HInstruction {
+  final String name;
+
+  factory HEmbeddedGlobalGet(
+    String name,
+    NativeBehavior nativeBehavior,
+    AbstractValue type,
+  ) {
+    final node = HEmbeddedGlobalGet._(name, type);
+    node.sideEffects.add(nativeBehavior.sideEffects);
+    if (nativeBehavior.useGvn) node.setUseGvn();
+    return node;
+  }
+
+  HEmbeddedGlobalGet._(this.name, super.type) : super._noInput();
+
+  @override
+  R accept<R>(HVisitor<R> visitor) => visitor.visitEmbeddedGlobalGet(this);
+
+  @override
+  _GvnType get _gvnType => _GvnType.embeddedGlobal;
+
+  @override
+  bool typeEquals(HInstruction other) => other is HEmbeddedGlobalGet;
+
+  @override
+  bool dataEquals(HEmbeddedGlobalGet other) => name == other.name;
+
+  @override
+  String toString() => 'HEmbeddedGlobalGet($name)';
+}

pkg/compiler/lib/src/ssa/tracer.dart

@@ -297,6 +297,11 @@ class HInstructionStringifier implements HVisitor<String> {
   @override
   String visitDivide(HDivide node) => handleInvokeBinary(node, 'Divide');
 
+  @override
+  String visitEmbeddedGlobalGet(HEmbeddedGlobalGet node) {
+    return 'EmbeddedGlobalGet: "${node.name}"';
+  }
+
   @override
   String visitExit(HExit node) => "Exit";