[Fuchsia] Fix SwiftShader ICD discovery

ANGLE needs to set VK_ICD_FILENAMES for the Vulkan loader to discover
SwiftShader's ICD. Enable this logic on Fuchsia.

Also updated ConcatenatePath() to handle absolute paths correctly.

Bug: chromium:1225002
Change-Id: Ib69be0d7dcaef09f1da9d411023e90a3b7b4fca2
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3292347
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>

src/common/system_utils.cpp

@@ -122,7 +122,7 @@ std::string ConcatenatePath(std::string first, std::string second)
     }
     if (IsFullPath(second))
     {
-        return first;
+        return second;
     }
     bool firstRedundantPathSeparator = first.find_last_of(GetPathSeparator()) == first.length() - 1;
     bool secondRedundantPathSeparator = second.find(GetPathSeparator()) == 0;

src/common/system_utils_unittest.cpp

@@ -121,7 +121,7 @@ TEST(SystemUtils, ConcatenatePath2FullPath)
 {
     std::string path1    = "/this/is/path1";
     std::string path2    = "/this/is/path2";
-    std::string expected = "/this/is/path1";
+    std::string expected = "/this/is/path2";
     EXPECT_EQ(ConcatenatePath(path1, path2), expected);
 }
 
@@ -169,7 +169,7 @@ TEST(SystemUtils, ConcatenatePath2FullPath)
 {
     std::string path1    = "C:\\this\\is\\path1";
     std::string path2    = "C:\\this\\is\\path2";
-    std::string expected = "C:\\this\\is\\path1";
+    std::string expected = "C:\\this\\is\\path2";
     EXPECT_EQ(ConcatenatePath(path1, path2), expected);
 }
 

src/common/vulkan/BUILD.gn

@@ -50,10 +50,13 @@ if (angle_enable_vulkan || angle_build_vulkan_system_info) {
       "vulkan_icd.h",
     ]
 
-    defines = [
-      "ANGLE_VK_LAYERS_DIR=\"$angle_data_dir\"",
-      "ANGLE_VK_MOCK_ICD_JSON=\"$angle_data_dir/VkICD_mock_icd.json\"",
-    ]
+    defines =
+        [ "ANGLE_VK_MOCK_ICD_JSON=\"$angle_data_dir/VkICD_mock_icd.json\"" ]
+
+    # On Fuchsia use validation layer provided by the SDK.
+    if (!is_fuchsia) {
+      defines += [ "ANGLE_VK_LAYERS_DIR=\"$angle_data_dir\"" ]
+    }
 
     data_deps = []
 
@@ -62,6 +65,8 @@ if (angle_enable_vulkan || angle_build_vulkan_system_info) {
       _sws_icd = "./$swiftshader_icd_file_name"
       if (is_win) {
         _sws_icd = ".\\\\$swiftshader_icd_file_name"
+      } else if (is_fuchsia) {
+        _sws_icd = "/pkg/$swiftshader_icd_file_name"
       }
 
       defines += [ "ANGLE_VK_SWIFTSHADER_ICD_JSON=\"${_sws_icd}\"" ]
@@ -126,7 +131,7 @@ if (angle_enable_vulkan) {
     group("vulkan_validation_layers") {
       data_deps = []
       if (is_fuchsia) {
-        data_deps += [ "//third_party/fuchsia-sdk:vulkan_validation" ]
+        data_deps += [ "//third_party/fuchsia-sdk/sdk/pkg/vulkan_layers:VkLayer_khronos_validation" ]
       } else {
         data_deps +=
             [ "$angle_vulkan_validation_layers_dir:vulkan_validation_layers" ]

src/common/vulkan/vulkan_icd.cpp

@@ -47,19 +47,15 @@ namespace vk
 namespace
 {
 
-// This function is unused on Android/Fuschia/GGP
-#if !defined(ANGLE_PLATFORM_ANDROID) && !defined(ANGLE_PLATFORM_FUCHSIA) && \
-    !defined(ANGLE_PLATFORM_GGP)
-const std::string WrapICDEnvironment(const char *icdEnvironment)
+ANGLE_MAYBE_UNUSED const std::string WrapICDEnvironment(const char *icdEnvironment)
 {
     // The libraries are bundled into the module directory
     std::string ret = ConcatenatePath(angle::GetModuleDirectory(), icdEnvironment);
     return ret;
 }
 
-constexpr char kLoaderLayersPathEnv[] = "VK_LAYER_PATH";
-constexpr char kLayerEnablesEnv[]     = "VK_LAYER_ENABLES";
-#endif
+ANGLE_MAYBE_UNUSED constexpr char kLoaderLayersPathEnv[] = "VK_LAYER_PATH";
+ANGLE_MAYBE_UNUSED constexpr char kLayerEnablesEnv[]     = "VK_LAYER_ENABLES";
 
 constexpr char kLoaderICDFilenamesEnv[]              = "VK_ICD_FILENAMES";
 constexpr char kANGLEPreferredDeviceEnv[]            = "ANGLE_PREFERRED_DEVICE";
@@ -115,8 +111,7 @@ ScopedVkLoaderEnvironment::ScopedVkLoaderEnvironment(bool enableValidationLayers
 // Changing CWD and setting environment variables makes no sense on Android,
 // since this code is a part of Java application there.
 // Android Vulkan loader doesn't need this either.
-#if !defined(ANGLE_PLATFORM_ANDROID) && !defined(ANGLE_PLATFORM_FUCHSIA) && \
-    !defined(ANGLE_PLATFORM_GGP)
+#if !defined(ANGLE_PLATFORM_ANDROID) && !defined(ANGLE_PLATFORM_GGP)
     if (icd == vk::ICD::Mock)
     {
         if (!setICDEnvironment(WrapICDEnvironment(ANGLE_VK_MOCK_ICD_JSON).c_str()))
@@ -133,6 +128,7 @@ ScopedVkLoaderEnvironment::ScopedVkLoaderEnvironment(bool enableValidationLayers
         }
     }
 #    endif  // defined(ANGLE_VK_SWIFTSHADER_ICD_JSON)
+
     if (mEnableValidationLayers || icd != vk::ICD::Default)
     {
         const auto &cwd = angle::GetCWD();
@@ -159,11 +155,14 @@ ScopedVkLoaderEnvironment::ScopedVkLoaderEnvironment(bool enableValidationLayers
     // Override environment variable to use the ANGLE layers.
     if (mEnableValidationLayers)
     {
+#    if defined(ANGLE_VK_LAYERS_DIR)
         if (!angle::PrependPathToEnvironmentVar(kLoaderLayersPathEnv, ANGLE_VK_LAYERS_DIR))
         {
             ERR() << "Error setting environment for Vulkan layers init.";
             mEnableValidationLayers = false;
         }
+#    endif  // defined(ANGLE_VK_LAYERS_DIR)
+
         if (!angle::PrependPathToEnvironmentVar(
                 kLayerEnablesEnv, "VK_VALIDATION_FEATURE_ENABLE_SYNCHRONIZATION_VALIDATION"))
         {