[CP] Add remap-sampler option to impellerc (#38228)

* [Impeller] order metal samplers according to declared order and not usage order (#38115)

* [Impeller] order metal samplers according to declared order and not use order

* ++

* always enabl remapping

* Revert "always enabl remapping"

This reverts commit 2fffb05.

* ++

* add test

* ++

* ++

* only run on mac

* Fix sampler offsets (#38170)

* [impeller] dont remap floats

* ++

* Update fragment_shader_test.dart

* ++:

* ++

ci/licenses_golden/tool_signature

@@ -1,2 +1,2 @@
-Signature: f6d8146c82d268e2e2549bf5019ebf07
+Signature: 9d0f7a4c4f53b80e33da848062bef937
 

impeller/compiler/compiler.cc

@@ -35,6 +35,45 @@ static CompilerBackend CreateMSLCompiler(const spirv_cross::ParsedIR& ir,
   sl_options.msl_version =
       spirv_cross::CompilerMSL::Options::make_msl_version(1, 2);
   sl_compiler->set_msl_options(sl_options);
+
+  // Set metal resource mappings to be consistent with location based mapping
+  // used on other backends when creating fragment shaders. This doesn't seem
+  // to work with the generated bindings for compute shaders, nor for certain
+  // shaders in the flutter/engine tree.
+  if (source_options.remap_samplers) {
+    std::vector<uint32_t> sampler_offsets;
+    ir.for_each_typed_id<spirv_cross::SPIRVariable>(
+        [&](uint32_t, const spirv_cross::SPIRVariable& var) {
+          if (var.storage != spv::StorageClassUniformConstant) {
+            return;
+          }
+          const auto spir_type = sl_compiler->get_type(var.basetype);
+          auto location = sl_compiler->get_decoration(
+              var.self, spv::Decoration::DecorationLocation);
+          if (spir_type.basetype ==
+              spirv_cross::SPIRType::BaseType::SampledImage) {
+            sampler_offsets.push_back(location);
+          }
+        });
+    if (sampler_offsets.size() > 0) {
+      auto start_offset =
+          *std::min_element(sampler_offsets.begin(), sampler_offsets.end());
+      for (auto offset : sampler_offsets) {
+        sl_compiler->add_msl_resource_binding({
+            .stage = spv::ExecutionModel::ExecutionModelFragment,
+            .basetype = spirv_cross::SPIRType::BaseType::SampledImage,
+            .binding = offset,
+            .count = 1u,
+            // A sampled image is both an image and a sampler, so both
+            // offsets need to be set or depending on the partiular shader
+            // the bindings may be incorrect.
+            .msl_texture = offset - start_offset,
+            .msl_sampler = offset - start_offset,
+        });
+      }
+    }
+  }
+
   return CompilerBackend(sl_compiler);
 }
 

impeller/compiler/impellerc_main.cc

@@ -73,6 +73,7 @@ bool Main(const fml::CommandLine& command_line) {
       switches.source_file_name, options.type, options.source_language,
       switches.entry_point);
   options.json_format = switches.json_format;
+  options.remap_samplers = switches.remap_samplers;
   options.gles_language_version = switches.gles_language_version;
 
   Reflector::Options reflector_options;

impeller/compiler/source_options.h

@@ -27,6 +27,7 @@ struct SourceOptions {
   uint32_t gles_language_version = 100;
   std::vector<std::string> defines;
   bool json_format = false;
+  bool remap_samplers = false;
 
   SourceOptions();
 

impeller/compiler/switches.cc

@@ -71,6 +71,9 @@ void Switches::PrintHelp(std::ostream& stream) {
   stream << "[optional] --depfile=<depfile_path>" << std::endl;
   stream << "[optional] --gles-language-verision=<number>" << std::endl;
   stream << "[optional] --json" << std::endl;
+  stream << "[optional] --remap-samplers (force metal sampler index to match "
+            "declared order)"
+         << std::endl;
 }
 
 Switches::Switches() = default;
@@ -125,6 +128,7 @@ Switches::Switches(const fml::CommandLine& command_line)
           command_line.GetOptionValueWithDefault("reflection-cc", "")),
       depfile_path(command_line.GetOptionValueWithDefault("depfile", "")),
       json_format(command_line.HasOption("json")),
+      remap_samplers(command_line.HasOption("remap-samplers")),
       gles_language_version(
           stoi(command_line.GetOptionValueWithDefault("gles-language-version",
                                                       "0"))),

impeller/compiler/switches.h

@@ -32,6 +32,7 @@ struct Switches {
   std::string depfile_path;
   std::vector<std::string> defines;
   bool json_format;
+  bool remap_samplers;
   SourceLanguage source_language = SourceLanguage::kUnknown;
   uint32_t gles_language_version;
   std::string entry_point;

impeller/fixtures/ordering/shader_with_samplers.frag

@@ -0,0 +1,15 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Declare samplers in different order than usage.
+uniform sampler2D textureA;
+uniform sampler2D textureB;
+
+out vec4 frag_color;
+
+void main() {
+  vec4 sample_1 = texture(textureB, vec2(1.0));
+  vec4 sample_2 = texture(textureA, vec2(1.0));
+  frag_color = sample_1 + sample_2;
+}

impeller/tools/impeller.gni

@@ -233,9 +233,13 @@ template("impellerc") {
     iplr = invoker.iplr
   }
   json = false
+  remap_samplers = false
   if (defined(invoker.json) && invoker.json) {
     json = invoker.json
   }
+  if (defined(invoker.remap_samplers) && invoker.remap_samplers) {
+    remap_samplers = invoker.remap_samplers
+  }
 
   # Not needed on every path.
   not_needed([
@@ -248,6 +252,8 @@ template("impellerc") {
   # Optional: invoker.intermediates_subdir specifies the subdirectory in which
   #           to put intermediates.
   # Optional: invoker.json Causes output format to be JSON instead of flatbuffer.
+  # Optional: invoker.remap_samplers Output metal samplers according to
+  #           declaration order instead of usage order.
 
   _impellerc(target_name) {
     sources = invoker.shaders
@@ -284,6 +290,9 @@ template("impellerc") {
     if (json) {
       args += [ "--json" ]
     }
+    if (remap_samplers) {
+      args += [ "--remap-samplers" ]
+    }
 
     if (sksl) {
       sl_intermediate =

lib/ui/fixtures/shaders/BUILD.gn

@@ -33,10 +33,23 @@ if (enable_unittests) {
     json = true
   }
 
+  impellerc("sampler_order_fixture") {
+    shaders = [
+      "//flutter/impeller/fixtures/ordering/shader_with_samplers.frag",
+      "//flutter/third_party/test_shaders/selman/glow_shader.frag",
+    ]
+    shader_target_flag = "--runtime-stage-metal"
+    intermediates_subdir = "iplr-remap"
+    sl_file_extension = "iplr"
+    iplr = true
+    remap_samplers = true
+  }
+
   test_fixtures("fixtures") {
     deps = [
       ":ink_sparkle",
       ":ink_sparkle_web",
+      ":sampler_order_fixture",
     ]
     fixtures = get_target_outputs(":ink_sparkle")
     dest = "$root_gen_dir/flutter/lib/ui"

testing/dart/fragment_shader_test.dart

@@ -332,6 +332,34 @@ void main() async {
     shader.dispose();
   });
 
+  // This test can't rely on actual pixels rendered since it needs to run on a
+  // metal shader on iOS. instead parse the source code.
+  test('impellerc orders samplers in metal shader according to declaration and not usage', () async {
+    if (!Platform.isMacOS) {
+      return;
+    }
+    final Directory directory = shaderDirectory('iplr-remap');
+    final String data = readAsStringLossy(File(path.join(directory.path, 'shader_with_samplers.frag.iplr')));
+
+    const String expected = 'texture2d<float> textureA [[texture(0)]],'
+      ' texture2d<float> textureB [[texture(1)]]';
+
+    expect(data, contains(expected));
+  });
+
+  test('impellerc orders samplers in metal shader according to declaration and not usage in glow', () async {
+    if (!Platform.isMacOS) {
+      return;
+    }
+    final Directory directory = shaderDirectory('iplr-remap');
+    final String data = readAsStringLossy(File(path.join(directory.path, 'glow_shader.frag.iplr')));
+
+    const String expected = 'texture2d<float> tInput [[texture(0)]], texture2d<float> tNoise [[texture(1)]], '
+      'sampler tInputSmplr [[sampler(0)]], sampler tNoiseSmplr [[sampler(1)]]';
+
+    expect(data, contains(expected));
+  });
+
   // Test all supported GLSL ops. See lib/spirv/lib/src/constants.dart
   final Map<String, FragmentProgram> iplrSupportedGLSLOpShaders = await _loadShaderAssets(
     path.join('supported_glsl_op_shaders', 'iplr'),
@@ -484,3 +512,8 @@ Image _createBlueGreenImageSync() {
     picture.dispose();
   }
 }
+
+// Ignore invalid utf8 since file is not actually text.
+String readAsStringLossy(File file) {
+  return convert.utf8.decode(file.readAsBytesSync(), allowMalformed: true);
+}

third_party/test_shaders/selman/LICENSE

@@ -0,0 +1,7 @@
+Copyright (c) 2022 by Selman Ay (https://codepen.io/selmanays/pen/yLVmEqY)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

third_party/test_shaders/selman/glow_shader.frag

@@ -0,0 +1,93 @@
+// Directional glow GLSL fragment shader.
+// Based on the "Let it Glow!" pen by "Selman Ay"
+// (https://codepen.io/selmanays/pen/yLVmEqY)
+precision highp float;
+
+// Float uniforms
+uniform float width;    // Width of the canvas
+uniform float height;   // Height of the canvas
+uniform float sourceX;  // X position of the light source
+uniform float
+    scrollFraction;     // Scroll fraction of the page in relation to the canvas
+uniform float density;  // Density of the "smoke" effect
+uniform float lightStrength;  // Strength of the light
+uniform float weight;         // Weight of the "smoke" effect
+
+// Sampler uniforms
+uniform sampler2D tInput;  // Input texture (the application canvas)
+uniform sampler2D tNoise;  // Some texture
+
+out vec4 fragColor;
+
+float sourceY = scrollFraction;
+vec2 resolution = vec2(width, height);
+vec2 lightSource = vec2(sourceX, sourceY);
+
+const int samples = 20;  // The number of "copies" of the canvas made to emulate
+                         // the "smoke" effect
+const float decay = 0.88;   // Decay of the light in each sample
+const float exposure = .9;  // The exposure to the light
+
+float random2d(vec2 uv) {
+  uv /= 256.;
+  vec4 tex = texture(tNoise, uv);
+  return mix(tex.r, tex.g, tex.a);
+}
+
+float random(vec3 xyz) {
+  return fract(sin(dot(xyz, vec3(12.9898, 78.233, 151.7182))) * 43758.5453);
+}
+
+vec4 sampleTexture(vec2 uv) {
+  vec4 textColor = texture(tInput, uv);
+  return textColor;
+}
+
+vec4 occlusion(vec2 uv, vec2 lightpos, vec4 objects) {
+  return (1. - smoothstep(0.0, lightStrength, length(lightpos - uv))) *
+         (objects);
+}
+
+vec4 fragment(vec2 uv, vec2 fragCoord) {
+  vec3 colour = vec3(0);
+
+  vec4 obj = sampleTexture(uv);
+  vec4 map = occlusion(uv, lightSource, obj);
+
+  float random = random(vec3(fragCoord, 1.0));
+  ;
+
+  float exposure = exposure + (sin(random) * .5 + 1.) * .05;
+
+  vec2 _uv = uv;
+  vec2 distance = (_uv - lightSource) * (1. / float(samples) * density);
+
+  float illumination_decay = 1.;
+  for (int i = 0; i < samples; i++) {
+    _uv -= distance;
+
+    float movement = random * 20. * float(i + 1);
+    float dither =
+        random2d(uv +
+                 mod(vec2(movement * sin(random * .5), -movement), 1000.)) *
+        2.;
+
+    vec4 stepped_map =
+        occlusion(uv, lightSource, sampleTexture(_uv + distance * dither));
+    stepped_map *= illumination_decay * weight;
+
+    illumination_decay *= decay;
+    map += stepped_map;
+  }
+
+  float lum = dot(map.rgb, vec3(0.2126, 0.7152, 0.0722));
+
+  colour += vec3(map.rgb * exposure);
+  return vec4(colour, lum);
+}
+
+void main() {
+  vec2 pos = gl_FragCoord.xy;
+  vec2 uv = pos / vec2(width, height);
+  fragColor = fragment(uv, pos);
+}

tools/licenses/lib/main.dart

@@ -1025,6 +1025,7 @@ class _RepositoryDirectory extends _RepositoryEntry implements LicenseSource {
            !entry.fullName.endsWith('third_party/json/docs') &&
            !entry.fullName.endsWith('third_party/ninja') &&
            !entry.fullName.endsWith('third_party/tinygltf') &&
+           !entry.fullName.endsWith('third_party/test_shaders') &&
             entry.name != '.ccls-cache' &&
             entry.name != '.cipd' &&
             entry.name != '.git' &&