IRGen: Redo fill ops

Instead of recording the current offset in the template, just
collect the fill ops into a vector and emit them at the
generic argument offset stored in the MetadataLayout.

For now this is NFC, but this allows the template to omit
entries for generic arguments entirely once some more
machinery is in place.

Author: slavapestov

lib/IRGen/GenMeta.cpp

@@ -2758,8 +2758,6 @@ namespace {
     struct FillOp {
       CanType Type;
       Optional<ProtocolConformanceRef> Conformance;
-      Size ToOffset;
-      bool IsRelative;
     };
 
     SmallVector<FillOp, 8> FillOps;
@@ -2836,7 +2834,10 @@ namespace {
       // fill indexes are word-indexed.
       Address metadataWords(IGF.Builder.CreateBitCast(metadataValue, IGM.Int8PtrPtrTy),
                             IGM.getPointerAlignment());
-      
+
+      auto genericReqtOffset = IGM.getMetadataLayout(Target)
+          .getGenericRequirementsOffset(IGF);
+
       for (auto &fillOp : FillOps) {
         llvm::Value *value;
         if (fillOp.Conformance) {
@@ -2846,20 +2847,12 @@ namespace {
         }
 
         auto dest = createPointerSizedGEP(IGF, metadataWords,
-                                          fillOp.ToOffset - AddressPoint);
+                                          genericReqtOffset.getStatic());
+        genericReqtOffset = genericReqtOffset.offsetBy(
+          IGF, IGM.getPointerSize());
 
-        // A far relative indirectable pointer.
-        if (fillOp.IsRelative) {
-          dest = IGF.Builder.CreateElementBitCast(dest,
-                                                  IGM.FarRelativeAddressTy);
-          IGF.emitStoreOfRelativeIndirectablePointer(value, dest,
-                                                     /*isFar*/ true);
-
-        // A direct pointer.
-        } else {
-          value = IGF.Builder.CreateBitCast(value, IGM.Int8PtrTy);
-          IGF.Builder.CreateStore(value, dest);
-        }
+        value = IGF.Builder.CreateBitCast(value, IGM.Int8PtrTy);
+        IGF.Builder.CreateStore(value, dest);
       }
 
       // Initialize the instantiated dependent value witness table, if we have
@@ -2894,12 +2887,6 @@ namespace {
       return f;
     }
 
-    void addFillOp(CanType type, Optional<ProtocolConformanceRef> conf,
-                   bool isRelative) {
-      FillOps.push_back({type, conf, getNextOffsetFromTemplateHeader(),
-                         isRelative });
-    }
-    
   public:
     void createMetadataAccessFunction() {
       (void) getGenericTypeMetadataAccessFunction(IGM, Target, ForDefinition);
@@ -2981,14 +2968,14 @@ namespace {
 
     template <class... T>
     void addGenericArgument(CanType type, T &&...args) {
-      addFillOp(type, None, /*relative*/ false);
+      FillOps.push_back({type, None});
       super::addGenericArgument(type, std::forward<T>(args)...);
     }
 
     template <class... T>
     void addGenericWitnessTable(CanType type, ProtocolConformanceRef conf,
                                 T &&...args) {
-      addFillOp(type, conf, /*relative*/ false);
+      FillOps.push_back({type, conf});
       super::addGenericWitnessTable(type, conf, std::forward<T>(args)...);
     }