Add an option to change the way nested variables are handled.

Only one value is implemented, which is the old way.

gen/nested.cpp

@@ -6,6 +6,42 @@
 #include "gen/logger.h"
 #include "gen/tollvm.h"
 
+#include "llvm/Support/CommandLine.h"
+namespace cl = llvm::cl;
+
+/// What the context pointer for a nested function looks like
+enum NestedCtxType {
+    /// Context is void*[] of pointers to variables.
+    /// Variables from higher levels are at the front.
+    NCArray,
+    
+    /// Context is a struct containing variables belonging to the parent function.
+    /// If the parent function itself has a parent function, one of the members is
+    /// a pointer to its context. (linked-list style)
+    // FIXME: implement
+    // TODO: Functions without any variables accessed by nested functions, but
+    //       with a parent whose variables are accessed, can use the parent's
+    //       context.
+    NCStruct,
+    
+    /// Context is an array of pointers to nested contexts. Each function with variables
+    /// accessed by nested functions puts them in a struct, and appends a pointer to that
+    /// struct to the array.
+    // FIXME: implement
+    NCHybrid
+};
+
+static cl::opt<NestedCtxType> nestedCtx("nested-ctx",
+    cl::desc("How to construct a nested function's context:"),
+    cl::ZeroOrMore,
+    cl::values(
+        clEnumValN(NCArray,  "array",  "Array of pointers to variables (including multi-level)"),
+        //clEnumValN(NCStruct, "struct", "Struct of variables (with multi-level via linked list)"),
+        //clEnumValN(NCHybrid, "hybrid", "Array of pointers to structs of variables"),
+        clEnumValEnd),
+    cl::init(NCArray));
+
+
 /****************************************************************************************/
 /*////////////////////////////////////////////////////////////////////////////////////////
 // NESTED VARIABLE HELPERS
@@ -13,6 +49,9 @@
 
 DValue* DtoNestedVariable(Loc loc, Type* astype, VarDeclaration* vd)
 {
+    ////////////////////////////////////
+    // Locate context value
+    
     Dsymbol* vdparent = vd->toParent2();
     assert(vdparent);
     
@@ -25,7 +64,7 @@ DValue* DtoNestedVariable(Loc loc, Type* astype, VarDeclaration* vd)
         return new DVarValue(astype, vd, val);
     }
     
-    // get it from the nested context
+    // get the nested context
     LLValue* ctx = 0;
     if (irfunc->decl->isMember2())
     {
@@ -38,6 +77,11 @@ DValue* DtoNestedVariable(Loc loc, Type* astype, VarDeclaration* vd)
     assert(ctx);
     
     assert(vd->ir.irLocal);
+    
+    ////////////////////////////////////
+    // Extract variable from nested context
+    
+    if (nestedCtx == NCArray) {
         LLValue* val = DtoBitCast(ctx, getPtrToType(getVoidPtrType()));
         val = DtoGEPi1(val, vd->ir.irLocal->nestedIndex);
         val = DtoLoad(val);
@@ -45,9 +89,14 @@ DValue* DtoNestedVariable(Loc loc, Type* astype, VarDeclaration* vd)
         val = DtoBitCast(val, vd->ir.irLocal->value->getType(), vd->toChars());
         return new DVarValue(astype, vd, val);
     }
+    else {
+        assert(0 && "Not implemented yet");
+    }
+}
 
 void DtoNestedInit(VarDeclaration* vd)
 {
+    if (nestedCtx == NCArray) {
         // alloca as usual if no value already
         if (!vd->ir.irLocal->value)
             vd->ir.irLocal->value = DtoAlloca(DtoType(vd->type), vd->toChars());
@@ -61,6 +110,10 @@ void DtoNestedInit(VarDeclaration* vd)
         
         DtoStore(val, gep);
     }
+    else {
+        assert(0 && "Not implemented yet");
+    }
+}
 
 LLValue* DtoNestedContext(Loc loc, Dsymbol* sym)
 {
@@ -92,6 +145,7 @@ LLValue* DtoNestedContext(Loc loc, Dsymbol* sym)
 }
 
 void DtoCreateNestedContext(FuncDeclaration* fd) {
+    if (nestedCtx == NCArray) {
         // construct nested variables array
         if (!fd->nestedVars.empty())
         {
@@ -177,10 +231,11 @@ void DtoCreateNestedContext(FuncDeclaration* fd) {
 
             // fixup nested result variable
         #if DMDV2
-        if (fd->vresult && fd->vresult->nestedrefs.dim) {
+            if (fd->vresult && fd->vresult->nestedrefs.dim)
         #else
-        if (fd->vresult && fd->vresult->nestedref) {
+            if (fd->vresult && fd->vresult->nestedref)
         #endif
+            {
                 Logger::println("nested vresult value: %s", fd->vresult->toChars());
                 LLValue* gep = DtoGEPi(nestedVars, 0, fd->vresult->ir.irLocal->nestedIndex);
                 LLValue* val = DtoBitCast(fd->vresult->ir.irLocal->value, getVoidPtrType());
@@ -188,3 +243,7 @@ void DtoCreateNestedContext(FuncDeclaration* fd) {
             }
         }
     }
+    else {
+        assert(0 && "Not implemented yet");
+    }
+}