Improvements and bug fixes for global type parameters

1. allow spReflection_FindTypeByName to accept arbitrary type expression string
2. allow const int generic value to be used as expression value, and as array size
3. various bug fixes in witness table specialization / function cloning during specializeIRForEntryPoint to avoid creating duplicate global values, not copying the right definition of a function from the other module, not cloning witness tables that are required by specializeGenerics etc.

Author: csyonghe

source/slang/check.cpp

@@ -6849,6 +6849,23 @@ namespace Slang
         return (!decl->primaryDecl) || (decl == decl->primaryDecl);
     }
 
+    RefPtr<Type> checkProperType(TranslationUnitRequest * tu, TypeExp typeExp)
+    {
+        RefPtr<Type> type;
+        DiagnosticSink nSink;
+        nSink.sourceManager = tu->compileRequest->sourceManager;
+        SemanticsVisitor visitor(
+            &nSink,
+            tu->compileRequest,
+            tu);
+        auto typeOut = visitor.CheckProperType(typeExp);
+        if (!nSink.errorCount)
+        {
+            type = typeOut.type;
+        }
+        return type;
+    }
+
     void validateEntryPoint(
         EntryPointRequest*  entryPoint)
     {
@@ -6956,15 +6973,9 @@ namespace Slang
             {
                 RefPtr<Expr> typeExpr = entryPoint->compileRequest->parseTypeString(entryPoint->getTranslationUnit(),
                     name, s);
-                DiagnosticSink nSink;
-                SemanticsVisitor visitor(
-                    &nSink,
-                    translationUnit->compileRequest,
-                    translationUnit);
-                auto typeOut = visitor.CheckProperType(TypeExp(typeExpr));
-                if (!nSink.errorCount)
-                {
-                    type = typeOut.type;
+                type = checkProperType(translationUnit, TypeExp(typeExpr));
+                if (type)
+                {
                     break;
                 }
             }

source/slang/compiler.h

@@ -319,6 +319,8 @@ namespace Slang
         ~CompileRequest();
 
         RefPtr<Expr> parseTypeString(TranslationUnitRequest * translationUnit, String typeStr, RefPtr<Scope> scope);
+        
+        Type* getTypeFromString(String typeStr);
 
         void parseTranslationUnit(
             TranslationUnitRequest* translationUnit);

source/slang/emit.cpp

@@ -7500,7 +7500,7 @@ String emitEntryPoint(
         // none of our target supports generics, or interfaces,
         // so we need to specialize those away.
         //
-        specializeGenerics(irModule);
+        specializeGenerics(irModule, sharedContext.target);
 
         // Debugging code for IR transformations...
 #if 0

source/slang/ir-insts.h

@@ -641,7 +641,8 @@ void specializeIRForEntryPoint(
 // Find suitable uses of the `specialize` instruction that
 // can be replaced with references to specialized functions.
 void specializeGenerics(
-    IRModule*   module);
+    IRModule*   module,
+    CodeGenTarget target);
 
 //