Shrink ObjC overhead (generated size and some runtime sizes)

NOTE: This is a binary breaking change as structure sizes have changed size
and/or order.

- Drop capturing field options, no other options were captured and other mobile
  targeted languages don't try to capture this sort information (saved 8
  bytes for every field defined (in static data and again in field descriptor
  instance size data).
- No longer generate/compile in the messages/enums in descriptor.proto. If
  developers need it, they should generate it and compile it in. Reduced the
  overhead of the core library.
- Compute the number of has_bits actually needs to avoid over reserving.
- Let the boolean single fields store via a has_bit to avoid storage, makes
  the common cases of the instance size smaller.
- Reorder some flags and down size the enums to contain the bits needed.
- Reorder the items in the structures to manually ensure they are are packed
  better (especially when generating 64bit code - 8 bytes for every field,
  16 bytes for every extension, instance sizes 8 bytes also).
- Split off the structure initialization so when the default is zero, the
  generated static storage doesn't need to reserve the space. This is batched
  at the message level, so all the fields for the message have to have zero
  defaults to get the saves. By definition all proto3 syntax  files fall into
  this case but it also saves space for the proto2 that use the standard
  defaults. (saves 8 bytes of static data for every field that had a zero
  default)
- Don't track the enums defined by a message. Nothing in the runtime needs it
  and it was just generation and runtime overhead. (saves 8 bytes per enum)
- Ensure EnumDescriptors are started up threadsafe in all cases.
- Split some of the Descriptor initialization into multiple methods so the
  generated code isn't padded with lots of zero/nil args.
- Change how oneof info is feed to the runtime enabling us to generate less
  static data (8 bytes saved per oneof for 64bit).
- Change how enum value informat is capture to pack the data and only decode
  it if it ends up being needed. Avoids padding issues causing bloat of 64bit,
  and removes the needs for extra pointers in addition to the data (just the
  data and one pointer now).

1 files changed, 35 insertions, 29 deletions

diff --git a/objectivec/GPBUtilities.m b/objectivec/GPBUtilities.m
index d4d6471f..3e9d11c0 100644
--- a/objectivec/GPBUtilities.m
+++ b/objectivec/GPBUtilities.m
@@ -145,9 +145,8 @@ void GPBSetHasIvar(GPBMessage *self, int32_t idx, uint32_t fieldNumber,
 }
 
 void GPBMaybeClearOneof(GPBMessage *self, GPBOneofDescriptor *oneof,
-                        uint32_t fieldNumberNotToClear) {
-  int32_t hasIndex = oneof->oneofDescription_->index;
-  uint32_t fieldNumberSet = GPBGetHasOneof(self, hasIndex);
+                        int32_t oneofHasIndex, uint32_t fieldNumberNotToClear) {
+  uint32_t fieldNumberSet = GPBGetHasOneof(self, oneofHasIndex);
   if ((fieldNumberSet == fieldNumberNotToClear) || (fieldNumberSet == 0)) {
     // Do nothing/nothing set in the oneof.
     return;
@@ -168,7 +167,7 @@ void GPBMaybeClearOneof(GPBMessage *self, GPBOneofDescriptor *oneof,
 
   // Set to nothing stored in the oneof.
   // (field number doesn't matter since setting to nothing).
-  GPBSetHasIvar(self, hasIndex, 1, NO);
+  GPBSetHasIvar(self, oneofHasIndex, 1, NO);
 }
 
 #pragma mark - IVar accessors
@@ -200,7 +199,8 @@ void GPBMaybeClearOneof(GPBMessage *self, GPBOneofDescriptor *oneof,
 //%            NAME$S                     GPBFileSyntax syntax) {
 //%  GPBOneofDescriptor *oneof = field->containingOneof_;
 //%  if (oneof) {
-//%    GPBMaybeClearOneof(self, oneof, GPBFieldNumber(field));
+//%    GPBMessageFieldDescription *fieldDesc = field->description_;
+//%    GPBMaybeClearOneof(self, oneof, fieldDesc->hasIndex, fieldDesc->number);
 //%  }
 //%  NSCAssert(self->messageStorage_ != NULL,
 //%            @"%@: All messages should have storage (from init)",
@@ -321,7 +321,8 @@ void GPBSetRetainedObjectIvarWithFieldInternal(GPBMessage *self,
     // oneof.
     GPBOneofDescriptor *oneof = field->containingOneof_;
     if (oneof) {
-      GPBMaybeClearOneof(self, oneof, GPBFieldNumber(field));
+      GPBMessageFieldDescription *fieldDesc = field->description_;
+      GPBMaybeClearOneof(self, oneof, fieldDesc->hasIndex, fieldDesc->number);
     }
     // Clear "has" if they are being set to nil.
     BOOL setHasValue = (value != nil);
@@ -476,15 +477,15 @@ void GPBSetMessageRawEnumField(GPBMessage *self, GPBFieldDescriptor *field,
   GPBSetInt32IvarWithFieldInternal(self, field, value, syntax);
 }
 
-//%PDDM-EXPAND IVAR_POD_ACCESSORS_DEFN(Bool, BOOL)
-// This block of code is generated, do not edit it directly.
-
 BOOL GPBGetMessageBoolField(GPBMessage *self,
                             GPBFieldDescriptor *field) {
   if (GPBGetHasIvarField(self, field)) {
-    uint8_t *storage = (uint8_t *)self->messageStorage_;
-    BOOL *typePtr = (BOOL *)&storage[field->description_->offset];
-    return *typePtr;
+    // Bools are stored in the has bits to avoid needing explicit space in the
+    // storage structure.
+    // (the field number passed to the HasIvar helper doesn't really matter
+    // since the offset is never negative)
+    GPBMessageFieldDescription *fieldDesc = field->description_;
+    return GPBGetHasIvar(self, (int32_t)(fieldDesc->offset), fieldDesc->number);
   } else {
     return field.defaultValue.valueBool;
   }
@@ -503,19 +504,18 @@ void GPBSetBoolIvarWithFieldInternal(GPBMessage *self,
                                      GPBFieldDescriptor *field,
                                      BOOL value,
                                      GPBFileSyntax syntax) {
+  GPBMessageFieldDescription *fieldDesc = field->description_;
   GPBOneofDescriptor *oneof = field->containingOneof_;
   if (oneof) {
-    GPBMaybeClearOneof(self, oneof, GPBFieldNumber(field));
+    GPBMaybeClearOneof(self, oneof, fieldDesc->hasIndex, fieldDesc->number);
   }
-  NSCAssert(self->messageStorage_ != NULL,
-            @"%@: All messages should have storage (from init)",
-            [self class]);
-#if defined(__clang_analyzer__)
-  if (self->messageStorage_ == NULL) return;
-#endif
-  uint8_t *storage = (uint8_t *)self->messageStorage_;
-  BOOL *typePtr = (BOOL *)&storage[field->description_->offset];
-  *typePtr = value;
+
+  // Bools are stored in the has bits to avoid needing explicit space in the
+  // storage structure.
+  // (the field number passed to the HasIvar helper doesn't really matter since
+  // the offset is never negative)
+  GPBSetHasIvar(self, (int32_t)(fieldDesc->offset), fieldDesc->number, value);
+
   // proto2: any value counts as having been set; proto3, it
   // has to be a non zero value.
   BOOL hasValue =
@@ -553,7 +553,8 @@ void GPBSetInt32IvarWithFieldInternal(GPBMessage *self,
                                       GPBFileSyntax syntax) {
   GPBOneofDescriptor *oneof = field->containingOneof_;
   if (oneof) {
-    GPBMaybeClearOneof(self, oneof, GPBFieldNumber(field));
+    GPBMessageFieldDescription *fieldDesc = field->description_;
+    GPBMaybeClearOneof(self, oneof, fieldDesc->hasIndex, fieldDesc->number);
   }
   NSCAssert(self->messageStorage_ != NULL,
             @"%@: All messages should have storage (from init)",
@@ -601,7 +602,8 @@ void GPBSetUInt32IvarWithFieldInternal(GPBMessage *self,
                                        GPBFileSyntax syntax) {
   GPBOneofDescriptor *oneof = field->containingOneof_;
   if (oneof) {
-    GPBMaybeClearOneof(self, oneof, GPBFieldNumber(field));
+    GPBMessageFieldDescription *fieldDesc = field->description_;
+    GPBMaybeClearOneof(self, oneof, fieldDesc->hasIndex, fieldDesc->number);
   }
   NSCAssert(self->messageStorage_ != NULL,
             @"%@: All messages should have storage (from init)",
@@ -649,7 +651,8 @@ void GPBSetInt64IvarWithFieldInternal(GPBMessage *self,
                                       GPBFileSyntax syntax) {
   GPBOneofDescriptor *oneof = field->containingOneof_;
   if (oneof) {
-    GPBMaybeClearOneof(self, oneof, GPBFieldNumber(field));
+    GPBMessageFieldDescription *fieldDesc = field->description_;
+    GPBMaybeClearOneof(self, oneof, fieldDesc->hasIndex, fieldDesc->number);
   }
   NSCAssert(self->messageStorage_ != NULL,
             @"%@: All messages should have storage (from init)",
@@ -697,7 +700,8 @@ void GPBSetUInt64IvarWithFieldInternal(GPBMessage *self,
                                        GPBFileSyntax syntax) {
   GPBOneofDescriptor *oneof = field->containingOneof_;
   if (oneof) {
-    GPBMaybeClearOneof(self, oneof, GPBFieldNumber(field));
+    GPBMessageFieldDescription *fieldDesc = field->description_;
+    GPBMaybeClearOneof(self, oneof, fieldDesc->hasIndex, fieldDesc->number);
   }
   NSCAssert(self->messageStorage_ != NULL,
             @"%@: All messages should have storage (from init)",
@@ -745,7 +749,8 @@ void GPBSetFloatIvarWithFieldInternal(GPBMessage *self,
                                       GPBFileSyntax syntax) {
   GPBOneofDescriptor *oneof = field->containingOneof_;
   if (oneof) {
-    GPBMaybeClearOneof(self, oneof, GPBFieldNumber(field));
+    GPBMessageFieldDescription *fieldDesc = field->description_;
+    GPBMaybeClearOneof(self, oneof, fieldDesc->hasIndex, fieldDesc->number);
   }
   NSCAssert(self->messageStorage_ != NULL,
             @"%@: All messages should have storage (from init)",
@@ -793,7 +798,8 @@ void GPBSetDoubleIvarWithFieldInternal(GPBMessage *self,
                                        GPBFileSyntax syntax) {
   GPBOneofDescriptor *oneof = field->containingOneof_;
   if (oneof) {
-    GPBMaybeClearOneof(self, oneof, GPBFieldNumber(field));
+    GPBMessageFieldDescription *fieldDesc = field->description_;
+    GPBMaybeClearOneof(self, oneof, fieldDesc->hasIndex, fieldDesc->number);
   }
   NSCAssert(self->messageStorage_ != NULL,
             @"%@: All messages should have storage (from init)",
@@ -812,7 +818,7 @@ void GPBSetDoubleIvarWithFieldInternal(GPBMessage *self,
   GPBBecomeVisibleToAutocreator(self);
 }
 
-//%PDDM-EXPAND-END (7 expansions)
+//%PDDM-EXPAND-END (6 expansions)
 
 // Aliases are function calls that are virtually the same.