Support compilation of Dawn on iOS.

BUG=dawn:225

Change-Id: I618552c55c8472adc25625733b59d972d7297f57
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/11040
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

src/common/Platform.h

@@ -17,15 +17,27 @@
 
 #if defined(_WIN32) || defined(_WIN64)
 #    define DAWN_PLATFORM_WINDOWS 1
+
 #elif defined(__linux__)
 #    define DAWN_PLATFORM_LINUX 1
 #    define DAWN_PLATFORM_POSIX 1
+
 #elif defined(__APPLE__)
 #    define DAWN_PLATFORM_APPLE 1
 #    define DAWN_PLATFORM_POSIX 1
+#    include <TargetConditionals.h>
+#    if TARGET_OS_IPHONE
+#        define DAWN_PLATFORM_IOS
+#    elif TARGET_OS_MAC
+#        define DAWN_PLATFORM_MACOS
+#    else
+#        error "Unsupported Apple platform."
+#    endif
+
 #elif defined(__Fuchsia__)
 #    define DAWN_PLATFORM_FUCHSIA 1
 #    define DAWN_PLATFORM_POSIX 1
+
 #else
 #    error "Unsupported platform."
 #endif

src/dawn_native/metal/BackendMTL.mm

@@ -15,15 +15,20 @@
 #include "dawn_native/metal/BackendMTL.h"
 
 #include "common/Constants.h"
+#include "common/Platform.h"
 #include "dawn_native/Instance.h"
 #include "dawn_native/MetalBackend.h"
 #include "dawn_native/metal/DeviceMTL.h"
 
-#import <IOKit/IOKitLib.h>
+#if defined(DAWN_PLATFORM_MACOS)
+#    import <IOKit/IOKitLib.h>
+#endif
 
 namespace dawn_native { namespace metal {
 
     namespace {
+
+#if defined(DAWN_PLATFORM_MACOS)
         struct PCIIDs {
             uint32_t vendorId;
             uint32_t deviceId;
@@ -150,6 +155,18 @@ namespace dawn_native { namespace metal {
             NSOperatingSystemVersion macOS10_11 = {10, 11, 0};
             return [NSProcessInfo.processInfo isOperatingSystemAtLeastVersion:macOS10_11];
         }
+#elif defined(DAWN_PLATFORM_IOS)
+        MaybeError GetDevicePCIInfo(id<MTLDevice> device, PCIIDs* ids) {
+            DAWN_UNUSED(device);
+            *ids = PCIIDs(0, 0);
+        }
+
+        bool IsMetalSupported() {
+            return true;
+        }
+#else
+#    error "Unsupported Apple platform."
+#endif
     }  // anonymous namespace
 
     // The Metal backend's Adapter.
@@ -201,14 +218,23 @@ namespace dawn_native { namespace metal {
     }
 
     std::vector<std::unique_ptr<AdapterBase>> Backend::DiscoverDefaultAdapters() {
-        NSArray<id<MTLDevice>>* devices = MTLCopyAllDevices();
-
         std::vector<std::unique_ptr<AdapterBase>> adapters;
-        for (id<MTLDevice> device in devices) {
-            adapters.push_back(std::make_unique<Adapter>(GetInstance(), device));
-        }
 
-        [devices release];
+        if (@available(macOS 10.12, *)) {
+            NSArray<id<MTLDevice>>* devices = MTLCopyAllDevices();
+
+            for (id<MTLDevice> device in devices) {
+                adapters.push_back(std::make_unique<Adapter>(GetInstance(), device));
+            }
+
+            [devices release];
+        } else if (@available(iOS 8.0, *)) {
+            // iOS only has a single device so MTLCopyAllDevices doesn't exist there.
+            adapters.push_back(
+                std::make_unique<Adapter>(GetInstance(), MTLCreateSystemDefaultDevice()));
+        } else {
+            UNREACHABLE();
+        }
         return adapters;
     }
 

src/dawn_native/metal/DeviceMTL.h

@@ -21,8 +21,9 @@
 #include "dawn_native/Device.h"
 #include "dawn_native/metal/Forward.h"
 
+#import <IOSurface/IOSurfaceRef.h>
 #import <Metal/Metal.h>
-#import <QuartzCore/CAMetalLayer.h>
+#import <QuartzCore/QuartzCore.h>
 
 #include <atomic>
 #include <memory>

src/dawn_native/metal/DeviceMTL.mm

@@ -76,10 +76,13 @@ namespace dawn_native { namespace metal {
     }
 
     void Device::InitTogglesFromDriver() {
+        if (@available(macOS 10.12, *)) {
+            bool emulateStoreAndMSAAResolve =
+                ![mMtlDevice supportsFeatureSet:MTLFeatureSet_macOS_GPUFamily1_v2];
+            SetToggle(Toggle::EmulateStoreAndMSAAResolve, emulateStoreAndMSAAResolve);
+        }
+
         // TODO(jiawei.shao@intel.com): check iOS feature sets
-        bool emulateStoreAndMSAAResolve =
-            ![mMtlDevice supportsFeatureSet:MTLFeatureSet_macOS_GPUFamily1_v2];
-        SetToggle(Toggle::EmulateStoreAndMSAAResolve, emulateStoreAndMSAAResolve);
 
         // TODO(jiawei.shao@intel.com): tighten this workaround when the driver bug is fixed.
         SetToggle(Toggle::AlwaysResolveIntoZeroLevelAndLayer, true);

src/dawn_native/metal/TextureMTL.h

@@ -17,6 +17,7 @@
 
 #include "dawn_native/Texture.h"
 
+#include <IOSurface/IOSurfaceRef.h>
 #import <Metal/Metal.h>
 
 namespace dawn_native { namespace metal {

src/dawn_native/metal/TextureMTL.mm

@@ -14,10 +14,9 @@
 
 #include "dawn_native/metal/TextureMTL.h"
 
+#include "common/Platform.h"
 #include "dawn_native/metal/DeviceMTL.h"
 
-#include <IOSurface/IOSurface.h>
-
 namespace dawn_native { namespace metal {
 
     namespace {
@@ -121,6 +120,14 @@ namespace dawn_native { namespace metal {
                     return DAWN_VALIDATION_ERROR("Unsupported IOSurface format");
             }
         }
+
+#if defined(DAWN_PLATFORM_MACOS)
+        MTLStorageMode kIOSurfaceStorageMode = MTLStorageModeManaged;
+#elif defined(DAWN_PLATFORM_IOS)
+        MTLStorageMode kIOSurfaceStorageMode = MTLStorageModePrivate;
+#else
+#    error "Unsupported Apple platform."
+#endif
     }
 
     MTLPixelFormat MetalPixelFormat(dawn::TextureFormat format) {
@@ -322,7 +329,7 @@ namespace dawn_native { namespace metal {
                      uint32_t plane)
         : TextureBase(device, descriptor, TextureState::OwnedInternal) {
         MTLTextureDescriptor* mtlDesc = CreateMetalTextureDescriptor(descriptor);
-        mtlDesc.storageMode = MTLStorageModeManaged;
+        mtlDesc.storageMode = kIOSurfaceStorageMode;
         mMtlTexture = [device->GetMTLDevice() newTextureWithDescriptor:mtlDesc
                                                              iosurface:ioSurface
                                                                  plane:plane];