[iOS] Better RPC guide and bug fix (#357)

apps/ios_rpc/README.md

@@ -4,20 +4,29 @@ This folder contains iOS RPC app that allows us to launch an rpc server on a iOS
 and connect to it through python script and do testing on the python side as normal TVM RPC.
 You will need XCode and an iOS device to use this.
 
+
+## Building
+Before start, please run ```init_proj.py``` to update XCode developer metadata. After this step, open
+```tvmrpc.xcodeproj``` by using XCode, build the App and install the App on the phone. Usually, we
+**do not** use the iOS App directly. 
+
 ## Workflow
 Due to security restriction of iOS10. We cannot upload dynamic libraries to the App and load it from sandbox.
 Instead, we need to build a list of libraries, pack them into the app bundle, launch the RPC server and
 connect to test the bundled libraries. We use ```xcodebuild test``` to automate this process.
-See [tests/ios_rpc_test.py](tests/ios_rpc_test.py) for an example.
 
-## Environment Variables
-To use the utilities, you need to configure the following environment variables
+The test script [tests/ios_rpc_test.py](tests/ios_rpc_test.py) is a good template for the workflow. With this 
+script, we don't need to manually operate the iOS App, this script will build the app, run it and collect the results automatically. 
+
+ To run the script,  you need to configure the following environment variables
 
-- ```TVM_IOS_CODESIGN``` The signature you use to codesign the app and libraries(e.g. ```iPhone Developer: Name (XXXX)```)
+- ```TVM_IOS_CODESIGN``` The signature you use to codesign the app and libraries (e.g. ```iPhone Developer: Name (XXXX)```)
 - ```TVM_IOS_RPC_ROOT``` The root directory of the iOS rpc project
+- ```TVM_IOS_RPC_PROXY_HOST``` The RPC proxy address
+- ```TVM_IOS_RPC_DESTINATION``` The Xcode target device(e.g. ```platform=iOS,name=xxxx```)
 
-## Launch RPC from XCode IDE
-Let us first explain how it works, the project look for ```rpc_config.txt``` file in the project root folder.
+## How it works
+Let us explain how it works, the project look for ```rpc_config.txt``` file in the project root folder.
 The ```rpc_config.txt``` file should be in the following format:
 ```
 <url> <port> <key>
@@ -35,6 +44,5 @@ and connect to the specified RPC proxy, start serving loop.
 So if we want to start the RPC from XCode IDE, simply manually modify ```rpc_config.txt``` file and click test.
 Then connect to the proxy via the python script.
 
-## Use RPC via App
 We can also use the RPC App directly, by typing in the address and press connect to connect to the proxy.
 However, the restriction is we can only load the modules that are bundled to the App.

apps/ios_rpc/init_proj.py

+import argparse
+import re
+
+parser = argparse.ArgumentParser(description='Update tvmrpc.xcodeproj\
+ developer information')
+parser.add_argument('--org_unit', type=str, required=True,
+                    help='Your own Organization Unit.\n\
+                    The Organization Unit can be found by following:\n\
+                    1. Open Keychain Access.\n\
+                    2. Find out your own iPhone Developer certificate.\n\
+                    3. Right click certificate, choose ```Get Info```.\n\
+                    4. Read & copy your Organization Unit.')
+
+parser.add_argument('--bundle_identifier', type=str, required=False,
+                    default="tvmrpc",
+                    help='The new bundle identifier')
+
+args = parser.parse_args()
+org_unit = args.org_unit
+bundle_identifier = args.bundle_identifier
+
+fi = open("tvmrpc.xcodeproj/project.pbxproj")
+proj_config = fi.read()
+fi.close()
+
+proj_config = proj_config.replace("3FR42MXLK9", org_unit)
+proj_config = proj_config.replace("ml.dmlc.tvmrpc", bundle_identifier)
+fo = open("tvmrpc.xcodeproj/project.pbxproj", "w")
+fo.write(proj_config)
+fo.close()
\ No newline at end of file

src/runtime/metal/metal_device_api.mm

@@ -191,7 +191,7 @@ void MetalWorkspace::CopyDataFromTo(const void* from,
     }
   } else if (from_dev_type == kCPU && to_dev_type == kMetal) {
     id<MTLBuffer> to_buf = (__bridge id<MTLBuffer>)(to);
-    if (to_buf.storageMode == MTLStorageModeShared) {
+    if (to_buf.storageMode != MTLStorageModeShared) {
       id<MTLBuffer> temp = MetalThreadEntry::ThreadLocal()
           ->GetTempBuffer(ctx_to, size);
       memcpy([temp contents],