1 /* 2 * Copyright 2015 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkOpts_DEFINED 9 #define SkOpts_DEFINED 10 11 #include "include/private/base/SkSpan_impl.h" 12 #include "src/core/SkRasterPipelineOpList.h" 13 14 #include <cstddef> 15 #include <cstdint> 16 17 struct SkRasterPipeline_MemoryCtxPatch; 18 19 /** 20 * SkOpts (short for SkOptimizations) is a mechanism where we can ship with multiple implementations 21 * of a set of functions and dynamically choose the best one at runtime (e.g. the call to 22 * SkGraphics::Init(), which calls SkOpts::Init()) depending on the detected CPU features. This is 23 * also referred to as having "specializations" of a given function. 24 * 25 * For example, Skia might be compiled to support CPUs that only have the sse2 instruction set 26 * (https://en.wikipedia.org/wiki/X86_instruction_listings#SSE2_instructions) 27 * but may be run on a more modern CPU that supports AVX2 instructions. 28 * (https://en.wikipedia.org/wiki/Advanced_Vector_Extensions) 29 * SkOpts allow Skia to have two versions of a row-blitting function, one that uses normal C++ 30 * code (e.g. loops, scalar integer math) and one that makes use of the AVX2 vector types and 31 * intrinsic functions. This function is declared here in the SkOpts namespace, and then the 32 * implementation (see SkOpts.cpp) is deferred to a function of the same name in the sse2:: 33 * namespace (the minimum Skia is compiled with) using DEFINE_DEFAULT. 34 * 35 * All implementations of this blit function are done in a header file file in //src/opts 36 * (e.g. //src/opts/SkBlitRow_opts.h). ifdefs guard each of the implementations, such that only 37 * one implementation is possible for a given SK_CPU_SSE_LEVEL. This header will be compiled 38 * *multiple* times with a different SK_CPU_SSE_LEVEL each compilation. 39 * 40 * Each CPU instruction set that we want specializations for has a .cpp file in //src/opts which 41 * defines an Init() function that replaces the function pointers in the SkOpts namespace with the 42 * ones from the specialized namespace (e.g. hsw::). These .cpp files don't implement the 43 * specializations, they just refer to the specialization created in the header files (e.g. 44 * SkBlitRow_opts.h). 45 * 46 * At compile time: 47 * - SkOpts.cpp is compiled with the minimum CPU level (e.g. SSE2). Because this 48 * file includes all the headers in //src/opts/, those headers add "the default implementation" 49 * of all their functions to the SK_OPTS_NS namespace (e.g. sse2::blit_row_color32). 50 * - Each of the specialized .cpp files in //src/opts/ are compiled with their respective 51 * compiler flags. Because the specialized .cpp file includes the headers that implement the 52 * functions using intrinsics or other CPU-specific code, those specialized functions end up 53 * in the specialized namespace, e.g. (hsw::blit_row_color32). 54 * 55 * At link time, the default implementations and all specializations of all SkOpts functions are 56 * included in the resulting library/binary file. 57 * 58 * At runtime, SkOpts::Init() will run the appropriate Init functions that the current CPU level 59 * supports specializations for (e.g. Init_hsw, Init_ssse3). Note multiple Init functions can 60 * be called as CPU instruction sets are typically super sets of older instruction sets 61 */ 62 63 struct SkRasterPipelineStage; 64 65 namespace SkOpts { 66 // Call to replace pointers to portable functions with pointers to CPU-specific functions. 67 // Thread-safe and idempotent. 68 // Called by SkGraphics::Init(). 69 void Init(); 70 71 // We can't necessarily express the type of SkRasterPipeline stage functions here, 72 // so we just use this void(*)(void) as a stand-in. 73 using StageFn = void(*)(void); 74 extern StageFn ops_highp[kNumRasterPipelineHighpOps], just_return_highp; 75 extern StageFn ops_lowp [kNumRasterPipelineLowpOps ], just_return_lowp; 76 77 extern void (*start_pipeline_highp)(size_t,size_t,size_t,size_t, SkRasterPipelineStage*, 78 SkSpan<SkRasterPipeline_MemoryCtxPatch>, 79 uint8_t*); 80 extern void (*start_pipeline_lowp )(size_t,size_t,size_t,size_t, SkRasterPipelineStage*, 81 SkSpan<SkRasterPipeline_MemoryCtxPatch>, 82 uint8_t*); 83 84 extern size_t raster_pipeline_lowp_stride; 85 extern size_t raster_pipeline_highp_stride; 86 } // namespace SkOpts 87 88 #endif // SkOpts_DEFINED 89