[Impeller] make labeling APIs exclusively use std::string_view. (#55918)

Many of our labeling APIs accepted a std::string. When provided with a string literal (const char*), this would force the allocation of a new std::string object and a copy of the original char*. std::string_view is a view of either a std::string, or a const char* (or other), which allows an API that doesn not need to store the string to accept both without a copy. Of course, we can't store a std::string_view, as that doesn't provide memory ownership - so many of the GLES implementations will still copy the string_view into a string locally.

Also updates several of the debug labelling functions to no-op in release mode and removes some expensive interpolations that aren't super necessary.

Author: Jonah Williams

impeller/core/device_buffer.h

@@ -23,9 +23,9 @@ class DeviceBuffer {
                                     Range source_range,
                                     size_t offset = 0u);
 
-  virtual bool SetLabel(const std::string& label) = 0;
+  virtual bool SetLabel(std::string_view label) = 0;
 
-  virtual bool SetLabel(const std::string& label, Range range) = 0;
+  virtual bool SetLabel(std::string_view label, Range range) = 0;
 
   /// @brief Create a buffer view of this entire buffer.
   static BufferView AsBufferView(std::shared_ptr<DeviceBuffer> buffer);

impeller/core/host_buffer.cc

@@ -37,10 +37,6 @@ HostBuffer::HostBuffer(const std::shared_ptr<Allocator>& allocator)
 
 HostBuffer::~HostBuffer() = default;
 
-void HostBuffer::SetLabel(std::string label) {
-  label_ = std::move(label);
-}
-
 BufferView HostBuffer::Emplace(const void* buffer,
                                size_t length,
                                size_t align) {

impeller/core/host_buffer.h

@@ -30,10 +30,7 @@ class HostBuffer {
   static std::shared_ptr<HostBuffer> Create(
       const std::shared_ptr<Allocator>& allocator);
 
-  // |Buffer|
-  virtual ~HostBuffer();
-
-  void SetLabel(std::string label);
+  ~HostBuffer();
 
   //----------------------------------------------------------------------------
   /// @brief      Emplace uniform data onto the host buffer. Ensure that backend
@@ -169,7 +166,6 @@ class HostBuffer {
   size_t current_buffer_ = 0u;
   size_t offset_ = 0u;
   size_t frame_index_ = 0u;
-  std::string label_;
 };
 
 }  // namespace impeller

impeller/display_list/aiks_dl_basic_unittests.cc

@@ -94,7 +94,7 @@ TEST_P(AiksTest, CanRenderColorFilterWithInvertColorsDrawPaint) {
 namespace {
 bool GenerateMipmap(const std::shared_ptr<Context>& context,
                     std::shared_ptr<Texture> texture,
-                    std::string label) {
+                    std::string_view label) {
   auto buffer = context->CreateCommandBuffer();
   if (!buffer) {
     return false;
@@ -103,7 +103,7 @@ bool GenerateMipmap(const std::shared_ptr<Context>& context,
   if (!pass) {
     return false;
   }
-  pass->GenerateMipmap(std::move(texture), std::move(label));
+  pass->GenerateMipmap(std::move(texture), label);
 
   pass->EncodeCommands(context->GetResourceAllocator());
   return context->GetCommandQueue()->Submit({buffer}).ok();

impeller/entity/contents/atlas_contents.cc

@@ -94,8 +94,7 @@ bool AtlasContents::Render(const ContentContext& renderer,
     using FS = PorterDuffBlendPipeline::FragmentShader;
 
 #ifdef IMPELLER_DEBUG
-    pass.SetCommandLabel(
-        SPrintF("DrawAtlas Blend (%s)", BlendModeToString(blend_mode)));
+    pass.SetCommandLabel("DrawAtlas Blend");
 #endif  // IMPELLER_DEBUG
     pass.SetVertexBuffer(geometry_->CreateBlendVertexBuffer(host_buffer));
     pass.SetPipeline(
@@ -138,8 +137,7 @@ bool AtlasContents::Render(const ContentContext& renderer,
   using FS = VerticesUberShader::FragmentShader;
 
 #ifdef IMPELLER_DEBUG
-  pass.SetCommandLabel(
-      SPrintF("DrawAtlas Advanced Blend (%s)", BlendModeToString(blend_mode)));
+  pass.SetCommandLabel("DrawAtlas Advanced Blend");
 #endif  // IMPELLER_DEBUG
   pass.SetVertexBuffer(geometry_->CreateBlendVertexBuffer(host_buffer));
 

impeller/entity/contents/content_context.cc

@@ -493,12 +493,12 @@ fml::StatusOr<RenderTarget> ContentContext::MakeSubpass(
   if (context->GetCapabilities()->SupportsOffscreenMSAA() && msaa_enabled) {
     subpass_target = GetRenderTargetCache()->CreateOffscreenMSAA(
         *context, texture_size,
-        /*mip_count=*/mip_count, SPrintF("%s Offscreen", label.data()),
+        /*mip_count=*/mip_count, label,
         RenderTarget::kDefaultColorAttachmentConfigMSAA, depth_stencil_config);
   } else {
     subpass_target = GetRenderTargetCache()->CreateOffscreen(
         *context, texture_size,
-        /*mip_count=*/mip_count, SPrintF("%s Offscreen", label.data()),
+        /*mip_count=*/mip_count, label,
         RenderTarget::kDefaultColorAttachmentConfig, depth_stencil_config);
   }
   return MakeSubpass(label, subpass_target, command_buffer, subpass_callback);
@@ -520,7 +520,7 @@ fml::StatusOr<RenderTarget> ContentContext::MakeSubpass(
   if (!sub_renderpass) {
     return fml::Status(fml::StatusCode::kUnknown, "");
   }
-  sub_renderpass->SetLabel(SPrintF("%s RenderPass", label.data()));
+  sub_renderpass->SetLabel(label);
 
   if (!subpass_callback(*this, *sub_renderpass)) {
     return fml::Status(fml::StatusCode::kUnknown, "");

impeller/entity/contents/content_context.h

@@ -992,7 +992,7 @@ class ContentContext {
                              PipelineDescriptor& desc) {
           opts.ApplyToPipelineDescriptor(desc);
           desc.SetLabel(
-              SPrintF("%s V#%zu", desc.GetLabel().c_str(), variants_count));
+              SPrintF("%s V#%zu", desc.GetLabel().data(), variants_count));
         });
     std::unique_ptr<RenderPipelineHandleT> variant =
         std::make_unique<RenderPipelineHandleT>(std::move(variant_future));

impeller/entity/contents/test/recording_render_pass.cc

@@ -92,7 +92,7 @@ fml::Status RecordingRenderPass::Draw() {
 }
 
 // |RenderPass|
-void RecordingRenderPass::OnSetLabel(std::string label) {
+void RecordingRenderPass::OnSetLabel(std::string_view label) {
   return;
 }
 

impeller/entity/contents/test/recording_render_pass.h

@@ -69,7 +69,7 @@ class RecordingRenderPass : public RenderPass {
                     const std::unique_ptr<const Sampler>& sampler) override;
 
   // |RenderPass|
-  void OnSetLabel(std::string label) override;
+  void OnSetLabel(std::string_view label) override;
 
   // |RenderPass|
   bool OnEncodeCommands(const Context& context) const override;

impeller/entity/contents/texture_contents.cc

@@ -31,8 +31,8 @@ std::shared_ptr<TextureContents> TextureContents::MakeRect(Rect destination) {
   return contents;
 }
 
-void TextureContents::SetLabel(std::string label) {
-  label_ = std::move(label);
+void TextureContents::SetLabel(std::string_view label) {
+  label_ = label;
 }
 
 void TextureContents::SetDestinationRect(Rect rect) {