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, 41 insertions, 34 deletions

diff --git a/source/slang/check.cpp b/source/slang/check.cpp
index 6b8617c66..cc2954fc4 100644
--- a/source/slang/check.cpp
+++ b/source/slang/check.cpp
@@ -147,7 +147,7 @@ namespace Slang
             if (baseExpr)
             {
                 auto expr = new MemberExpr();
-                expr->Position = originalExpr->Position;
+                expr->loc = originalExpr->loc;
                 expr->BaseExpression = baseExpr;
                 expr->name = declRef.GetName();
                 expr->type = GetTypeForDeclRef(declRef);
@@ -157,7 +157,7 @@ namespace Slang
             else
             {
                 auto expr = new VarExpr();
-                expr->Position = originalExpr->Position;
+                expr->loc = originalExpr->loc;
                 expr->name = declRef.GetName();
                 expr->type = GetTypeForDeclRef(declRef);
                 expr->declRef = declRef;
@@ -173,7 +173,7 @@ namespace Slang
             SLANG_ASSERT(ptrLikeType);
 
             auto derefExpr = new DerefExpr();
-            derefExpr->Position = originalExpr->Position;
+            derefExpr->loc = originalExpr->loc;
             derefExpr->base = base;
             derefExpr->type = QualType(ptrLikeType->elementType);
 
@@ -217,7 +217,7 @@ namespace Slang
             if (lookupResult.isOverloaded())
             {
                 auto overloadedExpr = new OverloadedExpr();
-                overloadedExpr->Position = originalExpr->Position;
+                overloadedExpr->loc = originalExpr->loc;
                 overloadedExpr->type = QualType(
                     getSession()->getOverloadedType());
                 overloadedExpr->base = baseExpr;
@@ -823,7 +823,7 @@ namespace Slang
                 if(outToExpr)
                 {
                     auto toInitializerListExpr = new InitializerListExpr();
-                    toInitializerListExpr->Position = fromInitializerListExpr->Position;
+                    toInitializerListExpr->loc = fromInitializerListExpr->loc;
                     toInitializerListExpr->type = QualType(toType);
                     toInitializerListExpr->args = coercedArgs;
 
@@ -1007,7 +1007,7 @@ namespace Slang
                 castExpr = new ImplicitCastExpr();
             }
 
-            castExpr->Position = fromExpr->Position;
+            castExpr->loc = fromExpr->loc;
             castExpr->TargetType.type = toType;
             castExpr->type = QualType(toType);
             castExpr->Expression = fromExpr;
@@ -1042,7 +1042,7 @@ namespace Slang
             {
                 if(!isRewriteMode())
                 {
-                    getSink()->diagnose(fromExpr->Position, Diagnostics::typeMismatch, toType, fromExpr->type);
+                    getSink()->diagnose(fromExpr->loc, Diagnostics::typeMismatch, toType, fromExpr->type);
                 }
 
                 // Note(tfoley): We don't call `CreateErrorExpr` here, because that would
@@ -1190,7 +1190,7 @@ namespace Slang
             {
                 if (!isRewriteMode())
                 {
-                    getSink()->diagnose(expr->Position, Diagnostics::expectedIntegerConstantNotLiteral);
+                    getSink()->diagnose(expr->loc, Diagnostics::expectedIntegerConstantNotLiteral);
                 }
                 return nullptr;
             }
@@ -1234,7 +1234,7 @@ namespace Slang
                 // For now we will do this in a completely ad hoc fashion,
                 // but it would be nice to have some generic routine to
                 // do the needed type checking/coercion.
-                if(hlslUncheckedAttribute->nameToken.Content == "numthreads")
+                if(getText(hlslUncheckedAttribute->getName()) == "numthreads")
                 {
                     if(hlslUncheckedAttribute->args.Count() != 3)
                         return m;
@@ -1249,8 +1249,8 @@ namespace Slang
 
                     auto hlslNumThreadsAttribute = new HLSLNumThreadsAttribute();
 
-                    hlslNumThreadsAttribute->Position   = hlslUncheckedAttribute->Position;
-                    hlslNumThreadsAttribute->nameToken  = hlslUncheckedAttribute->nameToken;
+                    hlslNumThreadsAttribute->loc   = hlslUncheckedAttribute->loc;
+                    hlslNumThreadsAttribute->name       = hlslUncheckedAttribute->getName();
                     hlslNumThreadsAttribute->args       = hlslUncheckedAttribute->args;
                     hlslNumThreadsAttribute->x          = (int32_t) xVal->value;
                     hlslNumThreadsAttribute->y          = (int32_t) yVal->value;
@@ -1614,20 +1614,20 @@ namespace Slang
             this->function = functionNode;
             auto returnType = CheckProperType(functionNode->ReturnType);
             functionNode->ReturnType = returnType;
-            HashSet<String> paraNames;
+            HashSet<Name*> paraNames;
             for (auto & para : functionNode->GetParameters())
             {
                 checkDecl(para);
 
-                if (paraNames.Contains(para->name.Content))
+                if (paraNames.Contains(para->getName()))
                 {
                     if (!isRewriteMode())
                     {
-                        getSink()->diagnose(para, Diagnostics::parameterAlreadyDefined, para->name);
+                        getSink()->diagnose(para, Diagnostics::parameterAlreadyDefined, para->getName());
                     }
                 }
                 else
-                    paraNames.Add(para->name.Content);
+                    paraNames.Add(para->getName());
             }
             this->function = NULL;
             functionNode->SetCheckState(DeclCheckState::CheckedHeader);
@@ -2062,6 +2062,11 @@ namespace Slang
             return new ConstantIntVal(expr->integerValue);
         }
 
+        Name* getName(String const& text)
+        {
+            return getCompileRequest()->getNamePool()->getName(text);
+        }
+
         RefPtr<IntVal> TryConstantFoldExpr(
             InvokeExpr* invokeExpr)
         {
@@ -2127,7 +2132,7 @@ namespace Slang
             auto opName = funcDeclRef.GetName();
 
             // handle binary operators
-            if (opName == "-")
+            if (opName == getName("-"))
             {
                 if (argCount == 1)
                 {
@@ -2140,8 +2145,8 @@ namespace Slang
             }
 
             // simple binary operators
-#define CASE(OP)                                                        \
-            else if(opName == #OP) do {                             \
+#define CASE(OP)                                                    \
+            else if(opName == getName(#OP)) do {                    \
                 if(argCount != 2) return nullptr;                   \
                 resultValue = constArgVals[0] OP constArgVals[1];   \
             } while(0)
@@ -2152,8 +2157,8 @@ namespace Slang
 
             // binary operators with chance of divide-by-zero
             // TODO: issue a suitable error in that case
-#define CASE(OP)                                                        \
-            else if(opName == #OP) do {                             \
+#define CASE(OP)                                                    \
+            else if(opName == getName(#OP)) do {                    \
                 if(argCount != 2) return nullptr;                   \
                 if(!constArgVals[1]) return nullptr;                \
                 resultValue = constArgVals[0] OP constArgVals[1];   \
@@ -2445,7 +2450,7 @@ namespace Slang
                     // it must match what the parser installed in subscript declarations.
                     LookupResult lookupResult = LookUpLocal(
                         getSession(),
-                        this, "operator[]", aggTypeDeclRef);
+                        this, getName("operator[]"), aggTypeDeclRef);
                     if (!lookupResult.isValid())
                     {
                         goto fail;
@@ -2458,7 +2463,7 @@ namespace Slang
                     // we will construct a reference to it and try to call it
 
                     RefPtr<InvokeExpr> subscriptCallExpr = new InvokeExpr();
-                    subscriptCallExpr->Position = subscriptExpr->Position;
+                    subscriptCallExpr->loc = subscriptExpr->loc;
                     subscriptCallExpr->FunctionExpr = subscriptFuncExpr;
 
                     // TODO(tfoley): This path can support multiple arguments easily
@@ -4126,7 +4131,7 @@ namespace Slang
                 sb << ".";
             }
 
-            sb << declRef.GetName();
+            sb << getText(declRef.GetName());
 
             // If the parent declaration is a generic, then we need to print out its
             // signature
@@ -4179,7 +4184,7 @@ namespace Slang
                         if (!first) sb << ", ";
                         first = false;
 
-                        sb << genericTypeParam.GetName();
+                        sb << getText(genericTypeParam.GetName());
                     }
                     else if(auto genericValParam = paramDeclRef.As<GenericValueParamDecl>())
                     {
@@ -4188,7 +4193,7 @@ namespace Slang
 
                         formatType(sb, GetType(genericValParam));
                         sb << " ";
-                        sb << genericValParam.GetName();
+                        sb << getText(genericValParam.GetName());
                     }
                     else
                     {}
@@ -4286,7 +4291,7 @@ namespace Slang
                     }
                 }
 
-                String funcName;
+                Name* funcName = nullptr;
                 if (auto baseVar = funcExpr.As<VarExpr>())
                     funcName = baseVar->name;
                 else if(auto baseMemberRef = funcExpr.As<MemberExpr>())
@@ -4298,7 +4303,7 @@ namespace Slang
                 {
                     // There were multple equally-good candidates, but none actually usable.
                     // We will construct a diagnostic message to help out.
-                    if (funcName.Length() != 0)
+                    if (funcName)
                     {
                         if (!isRewriteMode())
                         {
@@ -4317,7 +4322,7 @@ namespace Slang
                 {
                     // There were multiple applicable candidates, so we need to report them.
 
-                    if (funcName.Length() != 0)
+                    if (funcName)
                     {
                         if (!isRewriteMode())
                         {
@@ -4559,7 +4564,7 @@ namespace Slang
                                 {
                                     if (!isRewriteMode())
                                     {
-                                        getSink()->diagnose(expr->Arguments[i], Diagnostics::argumentExpectedLValue, (*params)[i]->name);
+                                        getSink()->diagnose(expr->Arguments[i], Diagnostics::argumentExpectedLValue, (*params)[i]->getName());
                                     }
                                 }
                             }
@@ -4732,7 +4737,7 @@ namespace Slang
             IntegerLiteralValue         baseElementCount)
         {
             RefPtr<SwizzleExpr> swizExpr = new SwizzleExpr();
-            swizExpr->Position = memberRefExpr->Position;
+            swizExpr->loc = memberRefExpr->loc;
             swizExpr->base = memberRefExpr->BaseExpression;
 
             IntegerLiteralValue limitElement = baseElementCount;
@@ -4744,9 +4749,11 @@ namespace Slang
             bool anyDuplicates = false;
             bool anyError = false;
 
-            for (UInt i = 0; i < memberRefExpr->name.Length(); i++)
+            auto swizzleText = getText(memberRefExpr->name);
+
+            for (UInt i = 0; i < swizzleText.Length(); i++)
             {
-                auto ch = memberRefExpr->name[i];
+                auto ch = swizzleText[i];
                 int elementIndex = -1;
                 switch (ch)
                 {
@@ -5014,11 +5021,11 @@ namespace Slang
             // be loaded), and then put its declarations into
             // the current scope.
 
-            auto name = decl->nameToken.Content;
+            auto name = decl->moduleNameAndLoc.name;
             auto scope = decl->scope;
 
             // Try to load a module matching the name
-            auto importedModuleDecl = findOrImportModule(request, name, decl->nameToken.Position);
+            auto importedModuleDecl = findOrImportModule(request, name, decl->moduleNameAndLoc.loc);
 
             // If we didn't find a matching module, then bail out
             if (!importedModuleDecl)