[torque] Add constexpr String handling to Torque

This CL adds a 'constexpr String' type to Torque, which gets compiled
to 'const char*'.

It makes it easier to pass strings around in Torque files,
especially when trying to Print() them.

Bug: v8:7793
Change-Id: I2d4feac7012f5401f2b467475f8df086e46ac18a
Reviewed-on: https://chromium-review.googlesource.com/1104466
Commit-Queue: Théotime Grohens <theotime@google.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53814}

src/builtins/base.tq

@@ -26,7 +26,8 @@ type AbstractCode extends HeapObject generates 'TNode<AbstractCode>';
 type Code extends AbstractCode generates 'TNode<Code>';
 type JSReceiver extends HeapObject generates 'TNode<JSReceiver>';
 type Context extends HeapObject generates 'TNode<Context>';
-type String extends HeapObject generates 'TNode<String>';
+type String extends HeapObject generates 'TNode<String>'
+    constexpr 'const char*';
 type Oddball extends HeapObject generates 'TNode<Oddball>';
 type HeapNumber extends HeapObject generates 'TNode<HeapNumber>';
 type Number = Smi | HeapNumber;
@@ -145,6 +146,8 @@ const INTPTR_PARAMETERS: constexpr ParameterMode = 'INTPTR_PARAMETERS';
 
 extern macro Is64(): constexpr bool;
 
+extern macro Print(constexpr String);
+extern macro Print(constexpr String, Object);
 extern macro Print(Object);
 extern macro DebugBreak();
 extern macro ToInteger_Inline(Context, Object): Number;
@@ -339,6 +342,7 @@ extern macro Int32Constant(constexpr int31): int32;
 extern macro Int32Constant(constexpr int32): int32;
 extern macro SmiConstant(constexpr int31): Smi;
 extern macro BoolConstant(constexpr bool): bool;
+extern macro StringConstant(constexpr String): String;
 extern macro LanguageModeConstant(constexpr LanguageMode): LanguageMode;
 extern macro Int32Constant(constexpr ElementsKind): ElementsKind;
 
@@ -390,6 +394,13 @@ macro from_constexpr<A : type>(e: constexpr ElementsKind): A;
 from_constexpr<ElementsKind>(e: constexpr ElementsKind): ElementsKind {
   return Int32Constant(e);
 }
+macro from_constexpr<A: type>(s: constexpr String): A;
+from_constexpr<String>(s: constexpr String): String {
+  return StringConstant(s);
+}
+from_constexpr<Object>(s: constexpr String): Object {
+  return StringConstant(s);
+}
 
 macro convert<A : type>(i: int32): A;
 convert<Number>(i: int32): Number {

src/torque/implementation-visitor.cc

@@ -490,11 +490,10 @@ VisitResult ImplementationVisitor::Visit(NumberLiteralExpression* expr) {
 }
 
 VisitResult ImplementationVisitor::Visit(StringLiteralExpression* expr) {
-  std::string temp = GenerateNewTempVariable(TypeOracle::GetStringType());
-  source_out() << "StringConstant(\""
-               << expr->literal.substr(1, expr->literal.size() - 2) << "\");"
-               << std::endl;
-  return VisitResult{TypeOracle::GetStringType(), temp};
+  std::string temp = GenerateNewTempVariable(TypeOracle::GetConstStringType());
+  source_out() << "\"" << expr->literal.substr(1, expr->literal.size() - 2)
+               << "\";" << std::endl;
+  return VisitResult{TypeOracle::GetConstStringType(), temp};
 }
 
 VisitResult ImplementationVisitor::GetBuiltinCode(Builtin* builtin) {

src/torque/type-oracle.h

@@ -40,8 +40,8 @@ class TypeOracle : public ContextualClass<TypeOracle> {
     return Get().GetBuiltinType(OBJECT_TYPE_STRING);
   }
 
-  static const Type* GetStringType() {
-    return Get().GetBuiltinType(STRING_TYPE_STRING);
+  static const Type* GetConstStringType() {
+    return Get().GetBuiltinType(CONST_STRING_TYPE_STRING);
   }
 
   static const Type* GetIntPtrType() {

src/torque/types.cc

@@ -221,6 +221,7 @@ bool IsAssignableFrom(const Type* to, const Type* from) {
 bool IsCompatibleSignature(const Signature& sig, const TypeVector& types,
                            const std::vector<Label*>& labels) {
   auto i = sig.parameter_types.types.begin();
+  if (sig.parameter_types.types.size() > types.size()) return false;
   // TODO(danno): The test below is actually insufficient. The labels'
   // parameters must be checked too. ideally, the named part of
   // LabelDeclarationVector would be factored out so that the label count and

src/torque/types.h

@@ -25,7 +25,7 @@ static const char* const VOID_TYPE_STRING = "void";
 static const char* const ARGUMENTS_TYPE_STRING = "constexpr Arguments";
 static const char* const CONTEXT_TYPE_STRING = "Context";
 static const char* const OBJECT_TYPE_STRING = "Object";
-static const char* const STRING_TYPE_STRING = "String";
+static const char* const CONST_STRING_TYPE_STRING = "constexpr String";
 static const char* const CODE_TYPE_STRING = "Code";
 static const char* const INTPTR_TYPE_STRING = "intptr";
 static const char* const CONST_INT31_TYPE_STRING = "constexpr int31";