Bug 1604615 - Use optimized shader source in webrender. r=jrmuizel

Add a gecko pref "gfx.webrender.use-optimized-shaders". If enabled,
then when attempting to compile a webrender shader first look for the
optimized source. If the optimized source is not present, emit a
warning and fall back to the unoptimized source.

Use the optimized source by default in wrench, and add the flag
"--use-unoptimized-shaders" to override this.

Differential Revision: https://phabricator.services.mozilla.com/D70033

gfx/config/gfxVars.h

@@ -45,6 +45,7 @@ class gfxVarReceiver;
   _(UseWebRenderTripleBufferingWin, bool, false)                   \
   _(UseWebRenderCompositor, bool, false)                           \
   _(UseWebRenderProgramBinaryDisk, bool, false)                    \
+  _(UseWebRenderOptimizedShaders, bool, false)                     \
   _(UseWebRenderMultithreading, bool, false)                       \
   _(WebRenderMaxPartialPresentRects, int32_t, 0)                   \
   _(WebRenderDebugFlags, int32_t, 0)                               \

gfx/layers/wr/WebRenderBridgeParent.cpp

@@ -125,6 +125,10 @@ const char* gfx_wr_resource_path_override() {
   return resourcePath;
 }
 
+bool gfx_wr_use_optimized_shaders() {
+  return mozilla::gfx::gfxVars::UseWebRenderOptimizedShaders();
+}
+
 void gfx_critical_note(const char* msg) { gfxCriticalNote << msg; }
 
 void gfx_critical_error(const char* msg) { gfxCriticalError() << msg; }

gfx/thebes/gfxPlatform.cpp

@@ -3032,6 +3032,10 @@ void gfxPlatform::InitWebRenderConfig() {
         gfxConfig::IsEnabled(Feature::WEBRENDER));
   }
 
+  if (StaticPrefs::gfx_webrender_use_optimized_shaders_AtStartup()) {
+    gfxVars::SetUseWebRenderOptimizedShaders(gfxConfig::IsEnabled(Feature::WEBRENDER));
+  }
+
   if (Preferences::GetBool("gfx.webrender.software", false)) {
     gfxVars::SetUseSoftwareWebRender(gfxConfig::IsEnabled(Feature::WEBRENDER));
   }

gfx/webrender_bindings/src/bindings.rs

@@ -510,6 +510,7 @@ extern "C" {
     // by commenting out the path that adds an external image ID
     fn gfx_use_wrench() -> bool;
     fn gfx_wr_resource_path_override() -> *const c_char;
+    fn gfx_wr_use_optimized_shaders() -> bool;
     // TODO: make gfx_critical_error() work.
     // We still have problem to pass the error message from render/render_backend
     // thread to main thread now.
@@ -1142,6 +1143,8 @@ fn wr_device_new(gl_context: *mut c_void, pc: Option<&mut WrProgramCache>) -> De
         }
     };
 
+    let use_optimized_shaders = unsafe { gfx_wr_use_optimized_shaders() };
+
     let cached_programs = match pc {
         Some(cached_programs) => Some(Rc::clone(cached_programs.rc_get())),
         None => None,
@@ -1150,6 +1153,7 @@ fn wr_device_new(gl_context: *mut c_void, pc: Option<&mut WrProgramCache>) -> De
     Device::new(
         gl,
         resource_override_path,
+        use_optimized_shaders,
         upload_method,
         cached_programs,
         false,
@@ -1427,6 +1431,7 @@ pub extern "C" fn wr_window_new(
                 }
             }
         },
+        use_optimized_shaders: unsafe { gfx_wr_use_optimized_shaders() },
         renderer_id: Some(window_id.0),
         upload_method,
         scene_builder_hooks: Some(Box::new(APZCallbacks::new(window_id))),

gfx/webrender_bindings/webrender_ffi.h

@@ -23,6 +23,7 @@ bool is_glcontext_gles(void* glcontext_ptr);
 bool is_glcontext_angle(void* glcontext_ptr);
 bool gfx_use_wrench();
 const char* gfx_wr_resource_path_override();
+bool gfx_wr_use_optimized_shaders();
 void gfx_critical_note(const char* msg);
 void gfx_critical_error(const char* msg);
 void gecko_printf_stderr_output(const char* msg);

gfx/wr/webrender/src/device/gl.rs

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use super::super::shader_source::UNOPTIMIZED_SHADERS;
+use super::super::shader_source::{OPTIMIZED_SHADERS, UNOPTIMIZED_SHADERS};
 use api::{ColorF, ImageDescriptor, ImageFormat, MemoryReport};
 use api::{MixBlendMode, TextureTarget, VoidPtrToSizeFn};
 use api::units::*;
@@ -662,10 +662,17 @@ pub struct VBOId(gl::GLuint);
 #[derive(PartialEq, Eq, Hash, Debug, Copy, Clone)]
 struct IBOId(gl::GLuint);
 
-#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+#[derive(Clone, Debug)]
+enum ProgramSourceType {
+    Unoptimized,
+    Optimized(ShaderVersion),
+}
+
+#[derive(Clone, Debug)]
 pub struct ProgramSourceInfo {
     base_filename: &'static str,
     features: Vec<&'static str>,
+    source_type: ProgramSourceType,
     digest: ProgramSourceDigest,
 }
 
@@ -677,32 +684,63 @@ impl ProgramSourceInfo {
     ) -> Self {
 
         // Compute the digest. Assuming the device has a `ProgramCache`, this
-        // will always be needed, whereas the source is rarely needed. As such,
-        // we compute the hash by walking the static strings in the same order
-        // as we would when concatenating the source, to avoid heap-allocating
-        // in the common case.
-        //
-        // Note that we cheat a bit to make the hashing more efficient. First,
-        // the only difference between the vertex and fragment shader is a
-        // single deterministic define, so we don't need to hash both. Second,
-        // we precompute the digest of the expanded source file at build time,
-        // and then just hash that digest here.
+        // will always be needed, whereas the source is rarely needed.
 
         use std::collections::hash_map::DefaultHasher;
         use std::hash::Hasher;
 
         // Setup.
         let mut hasher = DefaultHasher::new();
-        let version = get_shader_version(&*device.gl());
-        let override_path = device.resource_override_path.as_ref();
-        let source_and_digest = UNOPTIMIZED_SHADERS.get(&name).expect("Shader not found");
+        let gl_version = get_shader_version(&*device.gl());
 
         // Hash the renderer name.
         hasher.write(device.capabilities.renderer_name.as_bytes());
 
+        let full_name = &Self::full_name(name, features);
+
+        let optimized_source = if device.use_optimized_shaders {
+            OPTIMIZED_SHADERS.get(&(gl_version, full_name)).or_else(|| {
+                warn!("Missing optimized shader source for {}", full_name);
+                None
+            })
+        } else {
+            None
+        };
+
+        let source_type = match optimized_source {
+            Some(source_and_digest) => {
+                // Optimized shader sources are used as-is, without any run-time processing.
+                // The vertex and fragment shaders are different, so must both be hashed.
+                // We use the hashes that were computed at build time, and verify it in debug builds.
+                if cfg!(debug_assertions) {
+                    let mut h = DefaultHasher::new();
+                    h.write(source_and_digest.vert_source.as_bytes());
+                    h.write(source_and_digest.frag_source.as_bytes());
+                    let d: ProgramSourceDigest = h.into();
+                    let digest = d.to_string();
+                    debug_assert_eq!(digest, source_and_digest.digest);
+                    hasher.write(digest.as_bytes());
+                } else {
+                    hasher.write(source_and_digest.digest.as_bytes());
+                }
+
+                ProgramSourceType::Optimized(gl_version)
+            }
+            None => {
+                // For non-optimized sources we compute the hash by walking the static strings
+                // in the same order as we would when concatenating the source, to avoid
+                // heap-allocating in the common case.
+                //
+                // Note that we cheat a bit to make the hashing more efficient. First, the only
+                // difference between the vertex and fragment shader is a single deterministic
+                // define, so we don't need to hash both. Second, we precompute the digest of the
+                // expanded source file at build time, and then just hash that digest here.
+                let override_path = device.resource_override_path.as_ref();
+                let source_and_digest = UNOPTIMIZED_SHADERS.get(&name).expect("Shader not found");
+
                 // Hash the prefix string.
                 build_shader_prefix_string(
-            version,
+                    gl_version,
                     &features,
                     ShaderKind::Vertex,
                     &name,
@@ -724,17 +762,35 @@ impl ProgramSourceInfo {
                     hasher.write(digest.as_bytes());
                 } else {
                     hasher.write(source_and_digest.digest.as_bytes());
+                }
+
+                ProgramSourceType::Unoptimized
+            }
         };
 
         // Finish.
         ProgramSourceInfo {
             base_filename: name,
             features: features.to_vec(),
+            source_type,
             digest: hasher.into(),
         }
     }
 
     fn compute_source(&self, device: &Device, kind: ShaderKind) -> String {
+        let full_name = Self::full_name(self.base_filename, &self.features);
+        match self.source_type {
+            ProgramSourceType::Optimized(gl_version) => {
+                let shader = OPTIMIZED_SHADERS
+                    .get(&(gl_version, &full_name))
+                    .unwrap_or_else(|| panic!("Missing optimized shader source for {}", full_name));
+
+                match kind {
+                    ShaderKind::Vertex => shader.vert_source.to_string(),
+                    ShaderKind::Fragment => shader.frag_source.to_string(),
+                }
+            },
+            ProgramSourceType::Unoptimized => {
                 let mut src = String::new();
                 device.build_shader_string(
                     &self.features,
@@ -744,6 +800,16 @@ impl ProgramSourceInfo {
                 );
                 src
             }
+        }
+    }
+
+    fn full_name(base_filename: &'static str, features: &[&'static str]) -> String {
+        if features.is_empty() {
+            base_filename.to_string()
+        } else {
+            format!("{}_{}", base_filename, features.join("_"))
+        }
+    }
 }
 
 #[cfg_attr(feature = "serialize_program", derive(Deserialize, Serialize))]
@@ -1015,6 +1081,9 @@ pub struct Device {
     // resources
     resource_override_path: Option<PathBuf>,
 
+    /// Whether to use shaders that have been optimized at build time.
+    use_optimized_shaders: bool,
+
     max_texture_size: i32,
     max_texture_layers: u32,
     cached_programs: Option<Rc<ProgramCache>>,
@@ -1250,6 +1319,7 @@ impl Device {
     pub fn new(
         mut gl: Rc<dyn gl::Gl>,
         resource_override_path: Option<PathBuf>,
+        use_optimized_shaders: bool,
         upload_method: UploadMethod,
         cached_programs: Option<Rc<ProgramCache>>,
         allow_pixel_local_storage_support: bool,
@@ -1408,7 +1478,8 @@ impl Device {
             ),
         };
 
-        let (depth_format, upload_method) = if renderer_name.starts_with("Software WebRender") {
+        let is_software_webrender = renderer_name.starts_with("Software WebRender");
+        let (depth_format, upload_method) = if is_software_webrender {
             (gl::DEPTH_COMPONENT16, UploadMethod::Immediate)
         } else {
             (gl::DEPTH_COMPONENT24, upload_method)
@@ -1449,6 +1520,9 @@ impl Device {
             gl::GlType::Gles => supports_extension(&extensions,"GL_EXT_blend_func_extended"),
         };
 
+        // Software webrender relies on the unoptimized shader source.
+        let use_optimized_shaders = use_optimized_shaders && !is_software_webrender;
+
         // On the android emulator, glShaderSource can crash if the source
         // strings are not null-terminated. See bug 1591945.
         let requires_null_terminated_shader_source = is_emulator;
@@ -1479,6 +1553,7 @@ impl Device {
             gl,
             base_gl: None,
             resource_override_path,
+            use_optimized_shaders,
             upload_method,
             inside_frame: false,
 

gfx/wr/webrender/src/renderer.rs

@@ -2192,6 +2192,7 @@ impl Renderer {
         let mut device = Device::new(
             gl,
             options.resource_override_path.clone(),
+            options.use_optimized_shaders,
             options.upload_method.clone(),
             options.cached_programs.take(),
             options.allow_pixel_local_storage_support,
@@ -6713,6 +6714,8 @@ bitflags! {
 pub struct RendererOptions {
     pub device_pixel_ratio: f32,
     pub resource_override_path: Option<PathBuf>,
+    /// Whether to use shaders that have been optimized at build time.
+    pub use_optimized_shaders: bool,
     pub enable_aa: bool,
     pub enable_dithering: bool,
     pub max_recorded_profiles: usize,
@@ -6783,6 +6786,7 @@ impl Default for RendererOptions {
         RendererOptions {
             device_pixel_ratio: 1.0,
             resource_override_path: None,
+            use_optimized_shaders: false,
             enable_aa: true,
             enable_dithering: false,
             debug_flags: DebugFlags::empty(),

gfx/wr/wrench/src/args.yaml

@@ -21,6 +21,9 @@ args:
       long: shaders
       help: Override path for shaders
       takes_value: true
+  - use_unoptimized_shaders:
+      long: use-unoptimized-shaders
+      help: Use unoptimized shaders rather than the shaders optimized at build-time
   - rebuild:
       short: r
       long: rebuild

gfx/wr/wrench/src/main.rs

@@ -657,6 +657,7 @@ fn main() {
         &mut window,
         events_loop.as_mut().map(|el| el.create_proxy()),
         res_path,
+        !args.is_present("use_unoptimized_shaders"),
         dp_ratio,
         save_type,
         dim,

gfx/wr/wrench/src/wrench.rs

@@ -232,6 +232,7 @@ impl Wrench {
         window: &mut WindowWrapper,
         proxy: Option<EventsLoopProxy>,
         shader_override_path: Option<PathBuf>,
+        use_optimized_shaders: bool,
         dp_ratio: f32,
         save_type: Option<SaveType>,
         size: DeviceIntSize,
@@ -274,6 +275,7 @@ impl Wrench {
         let opts = webrender::RendererOptions {
             device_pixel_ratio: dp_ratio,
             resource_override_path: shader_override_path,
+            use_optimized_shaders,
             recorder,
             enable_subpixel_aa: !no_subpixel_aa,
             debug_flags,

modules/libpref/init/StaticPrefList.yaml

@@ -4151,6 +4151,11 @@
   value: @IS_NIGHTLY_BUILD@
   mirror: once
 
+- name: gfx.webrender.use-optimized-shaders
+  type: bool
+  value: true
+  mirror: once
+
 #ifdef NIGHTLY_BUILD
   # Keep this pref hidden on non-nightly builds to avoid people accidentally
   # turning it on.