Add an explicit `Name` type

Fixes #23

Up to this point, the compiler has used the ordinary `String` type to represent declaration names, which means a bunch of lookup structures throughout the compiler were string-to-whatever maps, which can reduce efficiency.
It also means that things like the `Token` type end up carying a `String` by value and paying for things like reference-counting.

This change adds a `Name` type that is used to represent names of variables, types, macros, etc.
Names are cached and unique'd globally for a session, and the string-to-name mapping gets done during lexing.
From that point on, most mapping is from pointers, which should make all the various table lookups faster.

More importantly (possibly), this brings us one step closer to being able to pool-allocate the AST nodes.

1 files changed, 101 insertions, 70 deletions

diff --git a/source/slang/lower.cpp b/source/slang/lower.cpp
index 68f61f8a5..2c62a69a8 100644
--- a/source/slang/lower.cpp
+++ b/source/slang/lower.cpp
@@ -317,8 +317,8 @@ private:
 class PseudoVarDecl : public RefObject
 {
 public:
-    Token name;
-    SourceLoc Position;
+    NameLoc nameAndLoc;
+    SourceLoc loc;
     TypeExp type;
 };
 
@@ -339,7 +339,7 @@ public:
 class PseudoExpr : public RefObject
 {
 public:
-    SourceLoc Position;
+    SourceLoc loc;
     QualType type;
 };
 
@@ -388,9 +388,9 @@ static SourceLoc getPosition(LoweredExpr const& expr)
 {
     switch (expr.getFlavor())
     {
-    case LoweredExpr::Flavor::Expr:         return expr.getExpr()            ->Position;
-    case LoweredExpr::Flavor::Tuple:        return expr.getTupleExpr()       ->Position;
-    case LoweredExpr::Flavor::VaryingTuple: return expr.getVaryingTupleExpr()->Position;
+    case LoweredExpr::Flavor::Expr:         return expr.getExpr()            ->loc;
+    case LoweredExpr::Flavor::Tuple:        return expr.getTupleExpr()       ->loc;
+    case LoweredExpr::Flavor::VaryingTuple: return expr.getVaryingTupleExpr()->loc;
     default:
         SLANG_UNREACHABLE("all cases handled");
         return SourceLoc();
@@ -415,7 +415,7 @@ struct SharedLoweringContext
     CodeGenTarget   target;
 
     // A set of words reserved by the target
-    Dictionary<String, String> reservedWords;
+    HashSet<Name*> reservedWords;
 
 
     RefPtr<ModuleDecl>   loweredProgram;
@@ -477,15 +477,16 @@ struct LoweringVisitor
 
     CodeGenTarget getTarget() { return shared->target; }
 
-    bool isReservedWord(String const& name)
+    bool isReservedWord(Name* name)
     {
-        return shared->reservedWords.TryGetValue(name) != nullptr;
+        return shared->reservedWords.Contains(name);
     }
 
     void registerReservedWord(
-        String const&   name)
+        String const&   text)
     {
-        shared->reservedWords.Add(name, name);
+        Name* name = shared->compileRequest->getNamePool()->getName(text);
+        shared->reservedWords.Add(name);
     }
 
     void registerReservedWords()
@@ -781,7 +782,7 @@ struct LoweringVisitor
         Expr*    loweredExpr,
         Expr*    expr)
     {
-        loweredExpr->Position = expr->Position;
+        loweredExpr->loc = expr->loc;
         loweredExpr->type.type = lowerType(expr->type.type);
     }
 
@@ -796,19 +797,27 @@ struct LoweringVisitor
     }
 
     RefPtr<Expr> createUncheckedVarRef(
-        char const* name)
+        Name* name)
     {
         RefPtr<VarExpr> result = new VarExpr();
         result->name = name;
         return result;
     }
 
+
+    RefPtr<Expr> createUncheckedVarRef(
+        char const* name)
+    {
+        return createUncheckedVarRef(
+            shared->compileRequest->getNamePool()->getName(name));
+    }
+
     RefPtr<Expr> createSimpleVarRef(
         SourceLoc const& loc,
         VarDeclBase*        decl)
     {
         RefPtr<VarExpr> result = new VarExpr();
-        result->Position = loc;
+        result->loc = loc;
         result->type.type = decl->type.type;
         result->declRef = makeDeclRef(decl);
         result->name = decl->getName();
@@ -842,7 +851,7 @@ struct LoweringVisitor
         TupleVarDecl*           decl)
     {
         RefPtr<TupleExpr> result = new TupleExpr();
-        result->Position = loc;
+        result->loc = loc;
         result->type.type = decl->type.type;
 
         if (auto primaryDecl = decl->primaryDecl)
@@ -891,11 +900,11 @@ struct LoweringVisitor
             // If we are referencing a declaration that got tuple-ified,
             // then we need to produce a tuple expression as well.
 
-            return createTupleRef(expr->Position, tupleVarDecl);
+            return createTupleRef(expr->loc, tupleVarDecl);
         }
         else if (auto varyingTupleVarDecl = loweredDecl.asVaryingTupleDecl())
         {
-            return createVaryingTupleRef(expr->Position, varyingTupleVarDecl);
+            return createVaryingTupleRef(expr->loc, varyingTupleVarDecl);
         }
 
         RefPtr<VarExpr> loweredExpr = new VarExpr();
@@ -905,26 +914,31 @@ struct LoweringVisitor
         return LoweredExpr(loweredExpr);
     }
 
-    String generateName()
+    Name* getName(String const& text)
+    {
+        return shared->compileRequest->getNamePool()->getName(text);
+    }
+
+    Name* generateName()
     {
         int id = shared->nameCounter++;
 
         String result;
         result.append("SLANG_tmp_");
         result.append(id);
-        return result;
+        return getName(result);
     }
 
     RefPtr<Expr> moveTemp(RefPtr<Expr> expr)
     {
         RefPtr<Variable> varDecl = new Variable();
-        varDecl->name.Content = generateName();
+        varDecl->nameAndLoc.name = generateName();
         varDecl->type.type = expr->type.type;
         varDecl->initExpr = expr;
 
         addDecl(varDecl);
 
-        return createSimpleVarRef(expr->Position, varDecl);
+        return createSimpleVarRef(expr->loc, varDecl);
     }
 
     // The idea of this function is to take an expression that we plan to
@@ -953,7 +967,7 @@ struct LoweringVisitor
         if (auto tupleExpr = expr.asTuple())
         {
             RefPtr<TupleExpr> resultExpr = new TupleExpr();
-            resultExpr->Position = tupleExpr->Position;
+            resultExpr->loc = tupleExpr->loc;
             resultExpr->type = tupleExpr->type;
             if (tupleExpr->primaryExpr)
             {
@@ -973,7 +987,7 @@ struct LoweringVisitor
         else if (auto varyingTupleExpr = expr.asVaryingTuple())
         {
             RefPtr<VaryingTupleExpr> resultExpr = new VaryingTupleExpr();
-            resultExpr->Position = varyingTupleExpr->Position;
+            resultExpr->loc = varyingTupleExpr->loc;
             resultExpr->type = varyingTupleExpr->type;
             for (auto ee : varyingTupleExpr->elements)
             {
@@ -1057,7 +1071,7 @@ struct LoweringVisitor
                     rightExpr = maybeMoveTemp(rightExpr);
 
                     RefPtr<AggTypeCtorExpr> ctorExpr = new AggTypeCtorExpr();
-                    ctorExpr->Position = rightExpr->Position;
+                    ctorExpr->loc = rightExpr->loc;
                     ctorExpr->type.type = leftType;
                     ctorExpr->base.type = leftType;
 
@@ -1065,7 +1079,7 @@ struct LoweringVisitor
                     for (int ee = 0; ee < elementCount; ++ee)
                     {
                         RefPtr<SwizzleExpr> swizzleExpr = new SwizzleExpr();
-                        swizzleExpr->Position = rightExpr->Position;
+                        swizzleExpr->loc = rightExpr->loc;
                         swizzleExpr->type.type = rightVecType->elementType;
                         swizzleExpr->base = rightExpr;
                         swizzleExpr->elementCount = 1;
@@ -1104,19 +1118,24 @@ struct LoweringVisitor
         RefPtr<Expr>* link = nullptr;
     };
 
-    RefPtr<Expr> createSimpleVarExpr(char const* name)
+    RefPtr<Expr> createSimpleVarExpr(Name* name)
     {
         RefPtr<VarExpr> varExpr = new VarExpr();
         varExpr->name = name;
         return varExpr;
     }
 
+    RefPtr<Expr> createSimpleVarExpr(char const* name)
+    {
+        return createSimpleVarExpr(getName(name));
+    }
+
     RefPtr<InvokeExpr> createSeqExpr(
         RefPtr<Expr>    left,
         RefPtr<Expr>    right)
     {
         RefPtr<InfixExpr> seqExpr = new InfixExpr();
-        seqExpr->Position = left->Position;
+        seqExpr->loc = left->loc;
         seqExpr->type = right->type;
         seqExpr->FunctionExpr = createSimpleVarExpr(",");
         seqExpr->Arguments.Add(left);
@@ -1207,14 +1226,14 @@ struct LoweringVisitor
                     {
                         // LHS array element
                         RefPtr<IndexExpr> arrayElemExpr = new IndexExpr();
-                        arrayElemExpr->Position = leftExpr->Position;
+                        arrayElemExpr->loc = leftExpr->loc;
                         arrayElemExpr->type.type = leftArrayType->BaseType;
                         arrayElemExpr->BaseExpression = leftExpr;
                         arrayElemExpr->IndexExpression = createConstIntExpr(ee);
 
                         // RHS swizzle
                         RefPtr<SwizzleExpr> swizzleExpr = new SwizzleExpr();
-                        swizzleExpr->Position = rightExpr->Position;
+                        swizzleExpr->loc = rightExpr->loc;
                         swizzleExpr->type.type = rightVecType->elementType;
                         swizzleExpr->base = rightExpr;
                         swizzleExpr->elementCount = 1;
@@ -1315,7 +1334,7 @@ struct LoweringVisitor
         {
             RefPtr<VaryingTupleExpr> resultTuple = new VaryingTupleExpr();
             resultTuple->type.type = leftVaryingTuple->type.type;
-            resultTuple->Position = leftVaryingTuple->Position;
+            resultTuple->loc = leftVaryingTuple->loc;
 
             SLANG_RELEASE_ASSERT(resultTuple->type.type);
 
@@ -1344,7 +1363,7 @@ struct LoweringVisitor
 
             RefPtr<VaryingTupleExpr> resultTuple = new VaryingTupleExpr();
             resultTuple->type.type = leftVaryingTuple->type.type;
-            resultTuple->Position = leftVaryingTuple->Position;
+            resultTuple->loc = leftVaryingTuple->loc;
 
             SLANG_RELEASE_ASSERT(resultTuple->type.type);
 
@@ -1366,7 +1385,7 @@ struct LoweringVisitor
 
 
                 RefPtr<MemberExpr> rightElemExpr = new MemberExpr();
-                rightElemExpr->Position = rightSimpleExpr->Position;
+                rightElemExpr->loc = rightSimpleExpr->loc;
                 rightElemExpr->type.type = GetType(leftElem.originalFieldDeclRef);
                 rightElemExpr->declRef = leftElem.originalFieldDeclRef;
                 rightElemExpr->name = leftElem.originalFieldDeclRef.GetName();
@@ -1392,7 +1411,7 @@ struct LoweringVisitor
 
             RefPtr<VaryingTupleExpr> resultTuple = new VaryingTupleExpr();
             resultTuple->type.type = leftSimpleExpr->type.type;
-            resultTuple->Position = leftSimpleExpr->Position;
+            resultTuple->loc = leftSimpleExpr->loc;
 
             SLANG_RELEASE_ASSERT(resultTuple->type.type);
 
@@ -1413,7 +1432,7 @@ struct LoweringVisitor
 
 
                 RefPtr<MemberExpr> leftElemExpr = new MemberExpr();
-                leftElemExpr->Position = leftSimpleExpr->Position;
+                leftElemExpr->loc = leftSimpleExpr->loc;
                 leftElemExpr->type.type = GetType(rightElem.originalFieldDeclRef);
                 leftElemExpr->declRef = rightElem.originalFieldDeclRef;
                 leftElemExpr->name = rightElem.originalFieldDeclRef.GetName();
@@ -2038,7 +2057,7 @@ struct LoweringVisitor
         {
             if (auto varExpr = infixExpr->FunctionExpr.As<VarExpr>())
             {
-                if (varExpr->name == ",")
+                if (getText(varExpr->name) == ",")
                 {
                     // Call to "operator comma"
                     for (auto aa : infixExpr->Arguments)
@@ -2124,7 +2143,7 @@ struct LoweringVisitor
         Stmt* loweredStmt,
         Stmt* originalStmt)
     {
-        loweredStmt->Position = originalStmt->Position;
+        loweredStmt->loc = originalStmt->loc;
         loweredStmt->modifiers = originalStmt->modifiers;
     }
 
@@ -2190,7 +2209,9 @@ struct LoweringVisitor
         for (auto token : stmt->tokens)
         {
             if (token.type == TokenType::Identifier)
-                doSampleRateInputCheck(token.Content);
+            {
+                doSampleRateInputCheck(token.getName());
+            }
         }
 
         loweredStmt->tokens = stmt->tokens;
@@ -2284,7 +2305,7 @@ struct LoweringVisitor
             constExpr->integerValue = ii;
 
             RefPtr<VaryingTupleVarDecl> loweredVarDecl = new VaryingTupleVarDecl();
-            loweredVarDecl->Position = varDecl->Position;
+            loweredVarDecl->loc = varDecl->loc;
             loweredVarDecl->type = varType;
             loweredVarDecl->expr = LoweredExpr(constExpr);
 
@@ -2354,7 +2375,7 @@ struct LoweringVisitor
         RefPtr<Expr>    expr)
     {
         RefPtr<ExplicitCastExpr> castExpr = new ExplicitCastExpr();
-        castExpr->Position = expr->Position;
+        castExpr->loc = expr->loc;
         castExpr->type.type = type;
         castExpr->TargetType.type = type;
         castExpr->Expression = expr;
@@ -2521,7 +2542,7 @@ struct LoweringVisitor
         if (isBuildingStmt)
         {
             RefPtr<DeclStmt> declStmt = new DeclStmt();
-            declStmt->Position = decl->Position;
+            declStmt->loc = decl->loc;
             declStmt->decl = decl;
             addStmt(declStmt);
         }
@@ -2573,9 +2594,13 @@ struct LoweringVisitor
         // and ad hoc fashion, but longer term we'll want to do
         // something sytematic.
 
-        if (isReservedWord(decl->getName()))
+        auto name = decl->getName();
+        if (isReservedWord(name))
         {
-            decl->name.Content.append("_");
+            auto nameText = getText(name);
+            nameText.append("_");
+
+            decl->nameAndLoc.name = getName(nameText);
         }
     }
 
@@ -2610,8 +2635,8 @@ struct LoweringVisitor
     {
         registerLoweredDecl(loweredDecl, decl);
 
-        loweredDecl->Position = decl->Position;
-        loweredDecl->name = decl->getNameToken();
+        loweredDecl->loc = decl->loc;
+        loweredDecl->nameAndLoc = decl->nameAndLoc;
 
         // Deal with renaming - we shouldn't allow decls with names that are reserved words
         ensureDeclHasAValidName(loweredDecl);
@@ -3000,7 +3025,7 @@ struct LoweringVisitor
             SLANG_RELEASE_ASSERT(!info.initExpr);
             RefPtr<Expr> fieldInitExpr;
 
-            String fieldName = info.name + "_" + dd.GetName();
+            String fieldName = info.name + "_" + getText(dd.GetName());
 
             auto fieldType = GetType(dd);
 
@@ -3102,7 +3127,7 @@ struct LoweringVisitor
                 }
 
                 RefPtr<VarDeclBase> fieldVarDecl = info.varDeclClass.createInstance();
-                fieldVarDecl->name.Content = fieldName;
+                fieldVarDecl->nameAndLoc = NameLoc(getName(fieldName));
                 fieldVarDecl->type.type = fieldVarType;
 
                 addDecl(fieldVarDecl);
@@ -3132,10 +3157,10 @@ struct LoweringVisitor
         SyntaxClass<VarDeclBase>        varDeclClass,
         RefPtr<VarDeclBase>             originalVarDecl,
         String const&                   name,
-        RefPtr<Type>          tupleType,
+        RefPtr<Type>                    tupleType,
         DeclRef<AggTypeDecl>            tupleTypeDecl,
         TupleTypeModifier*              tupleTypeMod,
-        RefPtr<Expr>    initExpr,
+        RefPtr<Expr>                    initExpr,
         RefPtr<VarLayout>               primaryVarLayout,
         RefPtr<StructTypeLayout>        tupleTypeLayout)
     {
@@ -3144,14 +3169,14 @@ struct LoweringVisitor
 
         // We'll need a placeholder declaration to wrap the whole thing up:
         RefPtr<TupleVarDecl> tupleDecl = new TupleVarDecl();
-        tupleDecl->name.Content = name;
+        tupleDecl->nameAndLoc = NameLoc(getName(name));
 
         // First, if the tuple type had any "ordinary" data,
         // then we go ahead and create a declaration for that stuff
         if (tupleTypeMod->hasAnyNonTupleFields)
         {
             RefPtr<VarDeclBase> primaryVarDecl = varDeclClass.createInstance();
-            primaryVarDecl->name.Content = name;
+            primaryVarDecl->nameAndLoc.name = getName(name);
             primaryVarDecl->type.type = tupleType;
 
             primaryVarDecl->modifiers = originalVarDecl->modifiers;
@@ -3257,7 +3282,7 @@ struct LoweringVisitor
             auto tupleDecl = createTupleTypeVarDecls(
                 loweredDeclClass,
                 decl,
-                decl->getName(),
+                getText(decl->getName()),
                 loweredType.type,
                 tupleTypeMod,
                 loweredInit,
@@ -3276,7 +3301,7 @@ struct LoweringVisitor
                 auto tupleDecl = createTupleTypeVarDecls(
                     loweredDeclClass,
                     decl,
-                    decl->getName(),
+                    getText(decl->getName()),
                     loweredType.type,
                     elementTupleTypeMod,
                     nullptr,
@@ -3357,9 +3382,10 @@ struct LoweringVisitor
         }
     }
 
-    void doSampleRateInputCheck(String const& name)
+    void doSampleRateInputCheck(Name* name)
     {
-        if (name == "gl_SampleIndex")
+        auto text = getText(name);
+        if (text == "gl_SampleIndex")
         {
             setSampleRateFlag();
         }
@@ -3616,7 +3642,7 @@ struct LoweringVisitor
         RefPtr<Type>  type)
     {
         RefPtr<VarExpr> globalVarRef = new VarExpr();
-        globalVarRef->name = name;
+        globalVarRef->name = getName(name);
         globalVarRef->type.type = type;
         return globalVarRef;
     }
@@ -3939,7 +3965,7 @@ struct LoweringVisitor
         if (!globalVarExpr)
         {
             RefPtr<Variable> globalVarDecl = new Variable();
-            globalVarDecl->name.Content = info.name;
+            globalVarDecl->nameAndLoc.name = getName(info.name);
             globalVarDecl->type.type = type;
 
             ensureDeclHasAValidName(globalVarDecl);
@@ -3998,7 +4024,7 @@ struct LoweringVisitor
 
 
             RefPtr<VarExpr> globalVarRef = new VarExpr();
-            globalVarRef->Position = globalVarDecl->Position;
+            globalVarRef->loc = globalVarDecl->loc;
             globalVarRef->type.type = globalVarDecl->type.type;
             globalVarRef->declRef = makeDeclRef(globalVarDecl.Ptr());
             globalVarRef->name = globalVarDecl->getName();
@@ -4077,7 +4103,7 @@ struct LoweringVisitor
                     fieldVarChain.varDecl = fieldDeclRef.getDecl();
 
                     VaryingParameterInfo fieldInfo = info;
-                    fieldInfo.name = info.name + "_" + fieldDeclRef.GetName();
+                    fieldInfo.name = info.name + "_" + getText(fieldDeclRef.GetName());
                     fieldInfo.varChain = &fieldVarChain;
 
                     // Need to find the layout for the given field...
@@ -4119,6 +4145,7 @@ struct LoweringVisitor
         VaryingParameterDirection   direction)
     {
         auto name = originalVarDecl->getName();
+        auto nameText = getText(name);
         auto declRef = makeDeclRef(originalVarDecl.Ptr());
 
         VaryingParameterVarChain varChain;
@@ -4126,7 +4153,7 @@ struct LoweringVisitor
         varChain.varDecl = originalVarDecl;
 
         VaryingParameterInfo info;
-        info.name = name;
+        info.name = nameText;
         info.direction = direction;
         info.varChain = &varChain;
 
@@ -4134,11 +4161,11 @@ struct LoweringVisitor
         switch (direction)
         {
         case VaryingParameterDirection::Input:
-            info.name = "SLANG_in_" + name;
+            info.name = "SLANG_in_" + nameText;
             break;
 
         case VaryingParameterDirection::Output:
-            info.name = "SLANG_out_" + name;
+            info.name = "SLANG_out_" + nameText;
             break;
         }
 
@@ -4168,7 +4195,7 @@ struct LoweringVisitor
         LoweredExpr         loweredExpr)
     {
         RefPtr<VaryingTupleVarDecl> loweredDecl = new VaryingTupleVarDecl();
-        loweredDecl->name = originalVarDecl->name;
+        loweredDecl->nameAndLoc = originalVarDecl->nameAndLoc;
         loweredDecl->type = loweredType;
         loweredDecl->expr = loweredExpr;
 
@@ -4197,14 +4224,18 @@ struct LoweringVisitor
         // First, loer the entry-point function as an ordinary function:
         auto loweredEntryPointFunc = visitFunctionDeclBase(entryPointDecl).getDecl()->As<FunctionDeclBase>();
 
+        auto mainName = getName("main");
+
         // Now we will generate a `void main() { ... }` function to call the lowered code.
         RefPtr<FuncDecl> mainDecl = new FuncDecl();
         mainDecl->ReturnType.type = getSession()->getVoidType();
-        mainDecl->name.Content = "main";
+
+
+        mainDecl->nameAndLoc = NameLoc(mainName);
 
         // If the user's entry point was called `main` then rename it here
-        if (loweredEntryPointFunc->getName() == "main")
-            loweredEntryPointFunc->name.Content = "main_";
+        if (loweredEntryPointFunc->getName() == mainName)
+            loweredEntryPointFunc->nameAndLoc = NameLoc(getName("main_"));
 
         RefPtr<BlockStmt> bodyStmt = new BlockStmt();
         bodyStmt->scopeDecl = new ScopeDecl();
@@ -4229,8 +4260,8 @@ struct LoweringVisitor
             SLANG_RELEASE_ASSERT(paramLayout);
 
             RefPtr<Variable> localVarDecl = new Variable();
-            localVarDecl->Position = paramDecl->Position;
-            localVarDecl->name.Content = paramDecl->getName();
+            localVarDecl->loc = paramDecl->loc;
+            localVarDecl->nameAndLoc = paramDecl->getNameAndLoc();
             localVarDecl->type = lowerType(paramDecl->type);
 
             ensureDeclHasAValidName(localVarDecl);
@@ -4267,8 +4298,8 @@ struct LoweringVisitor
         if (!loweredEntryPointFunc->ReturnType->Equals(getSession()->getVoidType()))
         {
             resultVarDecl = new Variable();
-            resultVarDecl->Position = loweredEntryPointFunc->Position;
-            resultVarDecl->name.Content = "main_result";
+            resultVarDecl->loc = loweredEntryPointFunc->loc;
+            resultVarDecl->nameAndLoc = NameLoc(getName("main_result"));
             resultVarDecl->type = TypeExp(loweredEntryPointFunc->ReturnType);
 
             ensureDeclHasAValidName(resultVarDecl);
@@ -4335,7 +4366,7 @@ struct LoweringVisitor
         if (resultVarDecl)
         {
             VaryingParameterInfo info;
-            info.name = "SLANG_out_" + resultVarDecl->getName();
+            info.name = "SLANG_out_" + getText(resultVarDecl->getName());
             info.direction = VaryingParameterDirection::Output;
             info.varChain = nullptr;