Add some missing ops to the SPIR-V Transpiler

BUILD.gn

@@ -104,6 +104,7 @@ group("flutter") {
     public_deps += [
       "//flutter/flow:flow_unittests",
       "//flutter/fml:fml_unittests",
+      "//flutter/lib/spirv/test/exception_shaders:spirv_compile_exception_shaders",
       "//flutter/lib/ui:ui_unittests",
       "//flutter/runtime:no_dart_plugin_registrant_unittests",
       "//flutter/runtime:runtime_unittests",

ci/analyze.sh

@@ -64,6 +64,12 @@ analyze \
   --options "$FLUTTER_DIR/analysis_options.yaml" \
   "$SRC_DIR/out/host_debug_unopt/gen/sky/bindings/dart_ui/ui.dart"
 
+echo "Analyzing spirv library..."
+analyze \
+  --packages="$FLUTTER_DIR/lib/spirv/.dart_tool/package_config.json" \
+  --options "$FLUTTER_DIR/analysis_options.yaml" \
+  "$FLUTTER_DIR/lib/spirv"
+
 echo "Analyzing flutter_frontend_server..."
 analyze \
   --packages="$FLUTTER_DIR/flutter_frontend_server/.dart_tool/package_config.json" \

lib/spirv/README.md

@@ -0,0 +1,46 @@
+# SPIR-V Transpiler
+
+Note: This library is currently considered experimental until shader compilation is verified by engine unit tests, see the Testing section below for more details.
+
+A dart library for transpiling a subset of SPIR-V to the shader languages used by Flutter internally.
+
+- [SkSL](https://skia.org/docs/user/sksl/)
+- [GLSL ES 100](https://www.khronos.org/files/opengles_shading_language.pdf)
+- [GLSL ES 300](https://www.khronos.org/registry/OpenGL/specs/es/3.0/GLSL_ES_Specification_3.00.pdf)
+
+All exported symbols are documented in `lib/spirv.dart`.
+
+The supported subset of SPIR-V is specified in `lib/src/constants.dart`.
+
+If you're using GLSL to generate SPIR-V with `glslangValidator` or `shaderc`,
+the code will need to adhere to the following rules.
+
+- There must be a single vec4 output at location 0.
+- The output can only be written to from the main function.
+- `gl_FragCoord` can only be read from the main function, and its z and w components
+  have no meaning.
+- Control flow is prohibited aside from function calls and `return`.
+  `if`, `while`, `for`, `switch`, etc.
+- No inputs from other shader stages.
+- Only float, float-vector types, and square float-matrix types.
+- Only square matrices are supported.
+- Only built-in functions present in GLSL ES 100 are used.
+- Debug symbols must be stripped, you can use the `spirv-opt` `--strip_debug` flag.
+
+These rules may become less strict in future versions. Confirmant SPIR-V should succesfully transpile from the current version onwards.  In other words, a spir-v shader you use now that meets these rules should keep working, but the output of the transpiler may change for that shader.
+
+Support for textures, control flow, and structured types is planned, but not currently included.
+
+## Testing
+
+## Exception Tests
+
+Exception tests are compiled to the `spirv_unittests` target. These tests rely on the `.spvasm` (SPIR-V Assembly)  and `.glsl` files contained under `test/exception_shaders` in this directory. They are compiled to binary SPIR-V using `spirv-asm`, from the SwiftShader dependency, and each is verified by a test described in `test/spirv_exception_test.dart`. The purpose of these tests is to exercise every explicit failure path for shader transpilation. Each `glsl` or `spvasm` file should include a comment describing the failure that it is testing. The given files should be valid apart from the single failure case they are testing.
+
+These tests can be run alone by executing `./spirv_unittests` in the build-output directory.
+
+## Pixel Tests
+
+Pixel test are not yet checked in, and should run as part of unit-testing for each implementation of `dart:ui`. These tests aim to validate the correctness of transpilation to each target language. Each shader should render the color green #00FF00 for a correct transpilation, and any other color for failure. They will be a combination of `.spvasm` files and more-readable GLSL files that are compiled to SPIR-V via `glslang`, provided by the SwiftShader dependency. Information for pixel tests will be expanded in a follow-up PR.
+
+These tests will be able to be run alone by executing `./ui_unittests` in the build-output directory.

lib/spirv/lib/spirv.dart

@@ -0,0 +1,70 @@
+// 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.
+
+/// This library defines a transpiler for converting SPIR-V into SkSL or GLSL.
+// @dart = 2.12
+library spirv;
+
+import 'dart:convert';
+import 'dart:math';
+import 'dart:typed_data';
+
+// These parts only contain private members, all public
+// members are in this file (spirv.dart)
+part 'src/constants.dart';
+part 'src/transpiler.dart';
+part 'src/types.dart';
+
+/// The language to transpile to.
+enum TargetLanguage {
+  /// SkSL, for Skia.
+  sksl,
+
+  /// GLSL ES 1.00, for WebGL 1.
+  glslES,
+
+  /// GLSL ES 3.00, for WebGL 2.
+  glslES300,
+}
+
+/// The result of a transpilation.
+class TranspileResult {
+  /// Source code string in [language].
+  final String src;
+
+  /// The shader language in [src].
+  final TargetLanguage language;
+
+  /// The number of float uniforms used in this shader.
+  final int uniformFloatCount;
+
+  TranspileResult._(this.src, this.uniformFloatCount, this.language);
+}
+
+/// Thrown during transpilation due to malformed or unsupported SPIR-V.
+class TranspileException implements Exception {
+  /// The SPIR-V operator last read, or zero if there was none.
+  final int op;
+
+  /// Human readable message explaining the exception.
+  final String message;
+
+  @override
+  String toString() => '$op: $message';
+
+  TranspileException._(this.op, this.message);
+}
+
+/// Transpile the provided SPIR-V buffer into a string of the [target] lang.
+/// Throws an instance of [TranspileException] for malformed or unsupported
+/// SPIR-V.
+TranspileResult transpile(ByteBuffer spirv, TargetLanguage target) {
+  final _Transpiler t = _Transpiler(spirv.asUint32List(), target);
+  t.transpile();
+  return TranspileResult._(
+    t.src.toString(),
+    t.uniformFloatCount,
+    target,
+  );
+}

lib/spirv/lib/src/constants.dart

@@ -0,0 +1,132 @@
+// 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.
+// @dart = 2.12
+
+part of spirv;
+
+// This file contains a subset of SPIR-V constants defined at
+// https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html
+
+// Header constants
+const int _magicNumber = 0x07230203;
+
+// Supported ExecutionModes
+const int _originLowerLeft = 8;
+
+// Supported memory models
+const int _addressingModelLogical = 0;
+const int _memoryModelGLSL450 = 1;
+
+// Supported capabilities
+const int _capabilityMatrix = 0;
+const int _capabilityShader = 1;
+
+// Supported storage classes
+const int _storageClassUniformConstant = 0;
+const int _storageClassInput = 1;
+const int _storageClassOutput = 3;
+const int _storageClassFunction = 7;
+
+// Explicity supported decorations, others are ignored
+const int _decorationBuiltIn = 11;
+const int _decorationLocation = 30;
+
+// Explicitly supported builtin types
+const int _builtinFragCoord = 15;
+
+// Ignored ops that have no semantic impact
+const int _opSource = 3;
+const int _opSourceExtension = 4;
+const int _opName = 5;
+const int _opMemberName = 6;
+const int _opString = 7;
+const int _opLine = 8;
+
+// Supported instructions
+const int _opExtInstImport = 11;
+const int _opExtInst = 12;
+const int _opMemoryModel = 14;
+const int _opEntryPoint = 15;
+const int _opExecutionMode = 16;
+const int _opCapability = 17;
+const int _opTypeVoid = 19;
+const int _opTypeBool = 20;
+const int _opTypeFloat = 22;
+const int _opTypeVector = 23;
+const int _opTypeMatrix = 24;
+const int _opTypePointer = 32;
+const int _opTypeFunction = 33;
+const int _opConstantTrue = 41;
+const int _opConstantFalse = 42;
+const int _opConstant = 43;
+const int _opConstantComposite = 44;
+const int _opFunction = 54;
+const int _opFunctionParameter = 55;
+const int _opFunctionEnd = 56;
+const int _opFunctionCall = 57;
+const int _opVariable = 59;
+const int _opLoad = 61;
+const int _opStore = 62;
+const int _opAccessChain = 65;
+const int _opDecorate = 71;
+const int _opVectorShuffle = 79;
+const int _opCompositeConstruct = 80;
+const int _opCompositeExtract = 81;
+const int _opFNegate = 127;
+const int _opFAdd = 129;
+const int _opFSub = 131;
+const int _opFMul = 133;
+const int _opFDiv = 136;
+const int _opFMod = 141;
+const int _opVectorTimesScalar = 142;
+const int _opMatrixTimesScalar = 143;
+const int _opVectorTimesMatrix = 144;
+const int _opMatrixTimesVector = 145;
+const int _opMatrixTimesMatrix = 146;
+const int _opDot = 148;
+const int _opLabel = 248;
+const int _opReturn = 253;
+const int _opReturnValue = 254;
+
+// GLSL extension constants defined at
+// https://www.khronos.org/registry/spir-v/specs/unified1/GLSL.std.450.html
+
+// Supported GLSL extension name
+const String _glslStd450 = 'GLSL.std.450';
+
+// Supported GLSL ops
+const int _glslStd450Trunc = 3;
+const int _glslStd450FAbs = 4;
+const int _glslStd450FSign = 6;
+const int _glslStd450Floor = 8;
+const int _glslStd450Ceil = 9;
+const int _glslStd450Fract = 10;
+const int _glslStd450Radians = 11;
+const int _glslStd450Degrees = 12;
+const int _glslStd450Sin = 13;
+const int _glslStd450Cos = 14;
+const int _glslStd450Tan = 15;
+const int _glslStd450Asin = 16;
+const int _glslStd450Acos = 17;
+const int _glslStd450Atan = 18;
+const int _glslStd450Atan2 = 25;
+const int _glslStd450Pow = 26;
+const int _glslStd450Exp = 27;
+const int _glslStd450Log = 28;
+const int _glslStd450Exp2 = 29;
+const int _glslStd450Log2 = 30;
+const int _glslStd450Sqrt = 31;
+const int _glslStd450InverseSqrt = 32;
+const int _glslStd450FMin = 37;
+const int _glslStd450FMax = 40;
+const int _glslStd450FClamp = 43;
+const int _glslStd450FMix = 46;
+const int _glslStd450Step = 48;
+const int _glslStd450SmoothStep = 49;
+const int _glslStd450Length = 66;
+const int _glslStd450Distance = 67;
+const int _glslStd450Cross = 68;
+const int _glslStd450Normalize = 69;
+const int _glslStd450FaceForward = 70;
+const int _glslStd450Reflect = 71;