Remove OpenGL support (part 1)

Fixes #5475

This removes the OpenGL backend (but *not* the OpenGLCompute backend) from public use:

- Remove Target::OpenGL
- remove DeviceAPI::GLSL
- remove Func::glsl() and Func::shader()
- remove all OpenGL-specific apps and tests
- remove HalideRuntimeOpenGL.h
- remove some internal code that is OpenGL-only

Note that there is still internal code that needs trimming; since the OpenGLCompute backend uses some of the same code, and some of the same build deps, and some of the same runtime shared-library loading, I tried to err on the side of leaving code/buildrules/etc in place for now, with the plan to clean that up in subsequent PRs.

Note also that feature Target::EGL is still present, as I believe it is still useful in conjunction with OpenGLCompute.

.github/workflows/presubmit.yml

@@ -49,6 +49,5 @@ jobs:
           (cd test/error               && comm -23 <(ls *.{c,cpp} | sort) <(grep -P '^\s*#?\s*[A-Za-z0-9_.]+$' CMakeLists.txt | tr -d '# ' | sort) | tee missing_files && [ ! -s missing_files ])
           (cd test/generator           && comm -23 <(ls *.{c,cpp} | sort) <(grep -P '^\s*#?\s*[A-Za-z0-9_.]+$' CMakeLists.txt | tr -d '# ' | sort) | tee missing_files && [ ! -s missing_files ])
           (cd test/failing_with_issue  && comm -23 <(ls *.{c,cpp} | sort) <(grep -P '^\s*#?\s*[A-Za-z0-9_.]+$' CMakeLists.txt | tr -d '# ' | sort) | tee missing_files && [ ! -s missing_files ])
-          (cd test/opengl              && comm -23 <(ls *.{c,cpp} | sort) <(grep -P '^\s*#?\s*[A-Za-z0-9_.]+$' CMakeLists.txt | tr -d '# ' | sort) | tee missing_files && [ ! -s missing_files ])
           (cd test/performance         && comm -23 <(ls *.{c,cpp} | sort) <(grep -P '^\s*#?\s*[A-Za-z0-9_.]+$' CMakeLists.txt | tr -d '# ' | sort) | tee missing_files && [ ! -s missing_files ])
           (cd test/warning             && comm -23 <(ls *.{c,cpp} | sort) <(grep -P '^\s*#?\s*[A-Za-z0-9_.]+$' CMakeLists.txt | tr -d '# ' | sort) | tee missing_files && [ ! -s missing_files ])

.github/workflows/test.yml

@@ -148,12 +148,6 @@ jobs:
           libpng-dev \
           ninja-build
 
-        # TODO(srj): OpenGL is only needed to build the opengl tests (which we don't even run)...
-        sudo apt-get install \
-          freeglut3-dev \
-          libglu1-mesa-dev \
-          mesa-common-dev
-
     - name: Configure MacOS Host
       if: startsWith(matrix.host_os, 'macos')
       shell: bash
@@ -193,12 +187,6 @@ jobs:
           libjpeg-dev:i386 \
           libpng-dev:i386 \
 
-        # TODO(srj): OpenGL is only needed to build the opengl tests (which we don't even run)...
-        sudo apt-get install \
-          freeglut3-dev:i386 \
-          libglu1-mesa-dev:i386 \
-          mesa-common-dev:i386
-
     - name: Configure Arm32 Crosscompilation
       if: matrix.target_os == 'linux' && matrix.target_arch == 'arm' && matrix.target_bits == 32
       shell: bash
@@ -449,9 +437,8 @@ jobs:
         TEST_GROUPS_SERIAL="tutorial"
 
         # performance is never going to be reliable on VMs.
-        # opengl won't work on the buildbots.
         # auto_schedule is just flaky.
-        TEST_GROUPS_BROKEN="performance opengl auto_schedule"
+        TEST_GROUPS_BROKEN="performance auto_schedule"
 
         if [[ ${{matrix.target_bits}} == 32 ]]; then
           # TODO: Skip testing apps on 32-bit systems for now;
@@ -487,9 +474,8 @@ jobs:
         TEST_GROUPS_SERIAL="tutorial"
 
         # performance is never going to be reliable on VMs.
-        # opengl won't work on the buildbots.
         # auto_schedule is just flaky.
-        TEST_GROUPS_BROKEN="performance|opengl|auto_schedule"
+        TEST_GROUPS_BROKEN="performance|auto_schedule"
 
         export TEST_TMPDIR="${HALIDE_TEMP_DIR}"
         cd ${HALIDE_BUILD_DIR}

Makefile

@@ -466,7 +466,6 @@ SOURCE_FILES = \
   ImageParam.cpp \
   InferArguments.cpp \
   InjectHostDevBufferCopies.cpp \
-  InjectOpenGLIntrinsics.cpp \
   Inline.cpp \
   InlineReductions.cpp \
   IntegerDivisionTable.cpp \
@@ -560,7 +559,6 @@ SOURCE_FILES = \
   UnsafePromises.cpp \
   Util.cpp \
   Var.cpp \
-  VaryingAttributes.cpp \
   VectorizeLoops.cpp \
   WasmExecutor.cpp \
   WrapCalls.cpp
@@ -645,7 +643,6 @@ HEADER_FILES = \
   ImageParam.h \
   InferArguments.h \
   InjectHostDevBufferCopies.h \
-  InjectOpenGLIntrinsics.h \
   Inline.h \
   InlineReductions.h \
   IntegerDivisionTable.h \
@@ -728,7 +725,6 @@ HEADER_FILES = \
   UnsafePromises.h \
   Util.h \
   Var.h \
-  VaryingAttributes.h \
   VectorizeLoops.h \
   WrapCalls.h
 
@@ -779,7 +775,6 @@ RUNTIME_CPP_COMPONENTS = \
   msan \
   msan_stubs \
   opencl \
-  opengl \
   openglcompute \
   opengl_egl_context \
   opengl_glx_context \
@@ -851,7 +846,6 @@ RUNTIME_EXPORTED_INCLUDES = $(INCLUDE_DIR)/HalideRuntime.h \
                             $(INCLUDE_DIR)/HalideRuntimeHexagonDma.h \
                             $(INCLUDE_DIR)/HalideRuntimeHexagonHost.h \
                             $(INCLUDE_DIR)/HalideRuntimeOpenCL.h \
-                            $(INCLUDE_DIR)/HalideRuntimeOpenGL.h \
                             $(INCLUDE_DIR)/HalideRuntimeOpenGLCompute.h \
                             $(INCLUDE_DIR)/HalideRuntimeMetal.h	\
                             $(INCLUDE_DIR)/HalideRuntimeQurt.h \
@@ -1110,22 +1104,18 @@ CORRECTNESS_TESTS = $(shell ls $(ROOT_DIR)/test/correctness/*.cpp) $(shell ls $(
 PERFORMANCE_TESTS = $(shell ls $(ROOT_DIR)/test/performance/*.cpp)
 ERROR_TESTS = $(shell ls $(ROOT_DIR)/test/error/*.cpp)
 WARNING_TESTS = $(shell ls $(ROOT_DIR)/test/warning/*.cpp)
-OPENGL_TESTS := $(shell ls $(ROOT_DIR)/test/opengl/*.cpp)
 GENERATOR_EXTERNAL_TESTS := $(shell ls $(ROOT_DIR)/test/generator/*test.cpp)
 GENERATOR_EXTERNAL_TEST_GENERATOR := $(shell ls $(ROOT_DIR)/test/generator/*_generator.cpp)
 TUTORIALS = $(filter-out %_generate.cpp, $(shell ls $(ROOT_DIR)/tutorial/*.cpp))
 AUTO_SCHEDULE_TESTS = $(shell ls $(ROOT_DIR)/test/auto_schedule/*.cpp)
 
--include $(OPENGL_TESTS:$(ROOT_DIR)/test/opengl/%.cpp=$(BUILD_DIR)/test_opengl_%.d)
-
 test_correctness: $(CORRECTNESS_TESTS:$(ROOT_DIR)/test/correctness/%.cpp=quiet_correctness_%) $(CORRECTNESS_TESTS:$(ROOT_DIR)/test/correctness/%.c=quiet_correctness_%)
 test_performance: $(PERFORMANCE_TESTS:$(ROOT_DIR)/test/performance/%.cpp=performance_%)
 test_error: $(ERROR_TESTS:$(ROOT_DIR)/test/error/%.cpp=error_%)
 test_warning: $(WARNING_TESTS:$(ROOT_DIR)/test/warning/%.cpp=warning_%)
 test_tutorial: $(TUTORIALS:$(ROOT_DIR)/tutorial/%.cpp=tutorial_%)
 test_valgrind: $(CORRECTNESS_TESTS:$(ROOT_DIR)/test/correctness/%.cpp=valgrind_%)
 test_avx512: $(CORRECTNESS_TESTS:$(ROOT_DIR)/test/correctness/%.cpp=avx512_%)
-test_opengl: $(OPENGL_TESTS:$(ROOT_DIR)/test/opengl/%.cpp=opengl_%)
 test_auto_schedule: test_mullapudi2016 test_li2018 test_adams2019
 
 .PHONY: test_correctness_multi_gpu
@@ -1230,7 +1220,6 @@ ALL_TESTS = test_internal test_correctness test_error test_tutorial test_warning
 # For generator tests they time the compile time only. The times are recorded in CSV files.
 time_compilation_correctness: init_time_compilation_correctness $(CORRECTNESS_TESTS:$(ROOT_DIR)/test/correctness/%.cpp=time_compilation_test_%)
 time_compilation_performance: init_time_compilation_performance $(PERFORMANCE_TESTS:$(ROOT_DIR)/test/performance/%.cpp=time_compilation_performance_%)
-time_compilation_opengl: init_time_compilation_opengl $(OPENGL_TESTS:$(ROOT_DIR)/test/opengl/%.cpp=time_compilation_opengl_%)
 time_compilation_generator: init_time_compilation_generator $(GENERATOR_TESTS:$(ROOT_DIR)/test/generator/%_aottest.cpp=time_compilation_generator_%)
 
 init_time_compilation_%:
@@ -1250,14 +1239,6 @@ build_tests: $(CORRECTNESS_TESTS:$(ROOT_DIR)/test/correctness/%.cpp=$(BIN_DIR)/c
 	$(GENERATOR_EXTERNAL_TESTS:$(ROOT_DIR)/test/generator/%_jittest.cpp=$(BIN_DIR)/generator_jit_%) \
 	$(AUTO_SCHEDULE_TESTS:$(ROOT_DIR)/test/auto_schedule/%.cpp=$(BIN_DIR)/auto_schedule_%)
 
-# OpenGL doesn't build on every host platform we support (eg. ARM).
-.PHONY: build_opengl_tests
-build_opengl_tests: $(OPENGL_TESTS:$(ROOT_DIR)/test/opengl/%.cpp=$(BIN_DIR)/opengl_%)
-
-ifneq ($(WITH_OPENGL),)
-build_tests: build_opengl_tests
-endif
-
 clean_generator:
 	rm -rf $(BIN_DIR)/*.generator
 	rm -rf $(BIN_DIR)/*/runtime.a
@@ -1321,9 +1302,6 @@ $(BIN_DIR)/error_%: $(ROOT_DIR)/test/error/%.cpp $(BIN_DIR)/libHalide.$(SHARED_E
 $(BIN_DIR)/warning_%: $(ROOT_DIR)/test/warning/%.cpp $(BIN_DIR)/libHalide.$(SHARED_EXT) $(INCLUDE_DIR)/Halide.h
 	$(CXX) $(TEST_CXX_FLAGS) $(OPTIMIZE_FOR_BUILD_TIME) $< -I$(INCLUDE_DIR) $(TEST_LD_FLAGS) -o $@
 
-$(BIN_DIR)/opengl_%: $(ROOT_DIR)/test/opengl/%.cpp $(BIN_DIR)/libHalide.$(SHARED_EXT) $(INCLUDE_DIR)/Halide.h $(INCLUDE_DIR)/HalideRuntime.h $(INCLUDE_DIR)/HalideRuntimeOpenGL.h
-	$(CXX) $(TEST_CXX_FLAGS) $(OPTIMIZE_FOR_BUILD_TIME) $< -I$(INCLUDE_DIR) -I$(SRC_DIR) $(TEST_LD_FLAGS) $(OPENGL_LD_FLAGS) -o $@ -MMD -MF $(BUILD_DIR)/test_opengl_$*.d
-
 # Auto schedule tests that link against libHalide
 $(BIN_DIR)/auto_schedule_%: $(ROOT_DIR)/test/auto_schedule/%.cpp $(BIN_DIR)/libHalide.$(SHARED_EXT) $(INCLUDE_DIR)/Halide.h
 	$(CXX) $(TEST_CXX_FLAGS) $(OPTIMIZE_FOR_BUILD_TIME) $< -I$(INCLUDE_DIR) $(TEST_LD_FLAGS) -o $@
@@ -1874,11 +1852,6 @@ warning_%: $(BIN_DIR)/warning_%
 	cd $(TMP_DIR) ; $(CURDIR)/$< 2>&1 | egrep --q "^Warning"
 	@-echo
 
-opengl_%: $(BIN_DIR)/opengl_%
-	@-mkdir -p $(TMP_DIR)
-	cd $(TMP_DIR) ; $(CURDIR)/$< 2>&1
-	@-echo
-
 generator_jit_%: $(BIN_DIR)/generator_jit_%
 	@-mkdir -p $(TMP_DIR)
 	cd $(TMP_DIR) ; $(CURDIR)/$<
@@ -1928,9 +1901,6 @@ time_compilation_test_%: $(BIN_DIR)/test_%
 time_compilation_performance_%: $(BIN_DIR)/performance_%
 	$(TIME_COMPILATION) compile_times_performance.csv make -f $(THIS_MAKEFILE) $(@:time_compilation_performance_%=performance_%)
 
-time_compilation_opengl_%: $(BIN_DIR)/opengl_%
-	$(TIME_COMPILATION) compile_times_opengl.csv make -f $(THIS_MAKEFILE) $(@:time_compilation_opengl_%=opengl_%)
-
 time_compilation_generator_%: $(BIN_DIR)/%.generator
 	$(TIME_COMPILATION) compile_times_generator.csv make -f $(THIS_MAKEFILE) $(@:time_compilation_generator_%=$(FILTERS_DIR)/%.a)
 

README.md

@@ -6,7 +6,7 @@ currently targets:
 
 - CPU architectures: X86, ARM, MIPS, Hexagon, PowerPC
 - Operating systems: Linux, Windows, Mac OS X, Android, iOS, Qualcomm QuRT
-- GPU Compute APIs: CUDA, OpenCL, OpenGL, OpenGL Compute Shaders, Apple Metal,
+- GPU Compute APIs: CUDA, OpenCL, OpenGL Compute Shaders, Apple Metal,
   Microsoft Direct X 12
 
 Rather than being a standalone programming language, Halide is embedded in C++.
@@ -336,140 +336,7 @@ an older XCode which does not default to libc++.
 
 # Halide OpenGL/GLSL backend
 
-Halide's OpenGL backend offloads image processing operations to the GPU by
-generating GLSL-based fragment shaders.
-
-Compared to other GPU-based processing options such as CUDA and OpenCL, OpenGL
-has two main advantages: it is available on basically every desktop computer and
-mobile device, and it is generally well supported across different hardware
-vendors.
-
-The main disadvantage of OpenGL as an image processing framework is that the
-computational capabilities of fragment shaders are quite restricted. In general,
-the processing model provided by OpenGL is most suitable for filters where each
-output pixel can be expressed as a simple function of the input pixels. This
-covers a wide range of interesting operations like point-wise filters and
-convolutions; but a few common image processing operations such as histograms or
-recursive filters are notoriously hard to express in GLSL.
-
-#### Writing OpenGL-Based Filters
-
-To enable code generation for OpenGL, include `opengl` in the target specifier
-passed to Halide. Since OpenGL shaders are limited in their computational power,
-you must also specify a CPU target for those parts of the filter that cannot or
-should not be computed on the GPU. Examples of valid target specifiers are
-
-```
-host-opengl
-x86-opengl-debug
-```
-
-Adding `debug`, as in the second example, adds additional logging output and is
-highly recommended during development.
-
-By default, filters compiled for OpenGL targets run completely on the CPU.
-Execution on the GPU must be enabled for individual Funcs by appropriate
-scheduling calls.
-
-GLSL fragment shaders implicitly iterate over two spatial dimensions x,y and the
-color channel. Due to the way color channels handled in GLSL, only filters for
-which the color index is a compile-time constant can be scheduled. The main
-consequence is that the range of color variables must be explicitly specified
-for both input and output buffers before scheduling:
-
-```
-ImageParam input;
-Func f;
-Var x, y, c;
-f(x, y, c) = ...;
-
-input.set_bounds(2, 0, 3);   // specify color range for input
-f.bound(c, 0, 3);            // and output
-f.glsl(x, y, c);
-```
-
-#### JIT Compilation
-
-For JIT compilation Halide attempts to load the system libraries for opengl and
-creates a new context to use for each module. Windows is not yet supported.
-
-Examples for JIT execution of OpenGL-based filters can be found in test/opengl.
-
-#### AOT Compilation
-
-When AOT (ahead-of-time) compilation is used, Halide generates OpenGL-enabled
-object files that can be linked to and called from a host application. In
-general, this is fairly straightforward, but a few things must be taken care of.
-
-On Linux, OS X, and Android, Halide creates its own OpenGL context unless the
-current thread already has an active context. On other platforms you have to
-link implementations of the following two functions with your Halide code:
-
-```
-extern "C" int halide_opengl_create_context(void *) {
-    return 0;  // if successful
-}
-
-extern "C" void *halide_opengl_get_proc_addr(void *, const char *name) {
-    ...
-}
-```
-
-Halide allocates and deletes textures as necessary. Applications may manage the
-textures by hand by setting the `halide_buffer_t::device` field; this is most
-useful for reusing image data that is already stored in textures. Some
-rudimentary checks are performed to ensure that externally allocated textures
-have the correct format, but in general that's the responsibility of the
-application.
-
-It is possible to let render directly to the current framebuffer; to do this,
-set the `dev` field of the output buffer to the value returned by
-`halide_opengl_output_client_bound`. The example in apps/HelloAndroidGL
-demonstrates this technique.
-
-Some operating systems can delete the OpenGL context of suspended applications.
-If this happens, Halide needs to re-initialize itself with the new context after
-the application resumes. Call `halide_opengl_context_lost` to reset Halide's
-OpenGL state after this has happened.
-
-#### Limitations
-
-The current implementation of the OpenGL backend targets the common subset of
-OpenGL 2.0 and OpenGL ES 2.0 which is widely available on both mobile devices
-and traditional computers. As a consequence, only a subset of the Halide
-language can be scheduled to run using OpenGL. Some important limitations are:
-
-- Reductions cannot be implemented in GLSL and must be run on the CPU.
-
-- OpenGL ES 2.0 only supports uint8 buffers.
-
-  Support for floating point texture is available, but requires OpenGL (ES) 3.0
-  or the texture_float extension, which may not work on all mobile devices.
-
-- OpenGL ES 2.0 has very limited support for integer arithmetic. For maximum
-  compatibility, consider doing all computations using floating point, even when
-  using integer textures.
-
-- Only 2D images with 3 or 4 color channels can be scheduled. Images with one or
-  two channels require OpenGL (ES) 3.0 or the texture_rg extension.
-
-- Not all builtin functions provided by Halide are currently supported, for
-  example `fast_log`, `fast_exp`, `fast_pow`, `reinterpret`, bit operations,
-  `random_float`, `random_int` cannot be used in GLSL code.
-
-The maximum texture size in OpenGL is `GL_MAX_TEXTURE_SIZE`, which is often
-smaller than the image of interest; on mobile devices, for example,
-`GL_MAX_TEXTURE_SIZE` is commonly 2048. Tiling must be used to process larger
-images.
-
-Planned features:
-
-- Support for half-float textures and arithmetic
-
-- Support for integer textures and arithmetic
-
-(Note that OpenGL Compute Shaders are supported with a separate OpenGLCompute
-backend.)
+TODO: update this for OpenGLCompute, which is staying
 
 # Halide for Hexagon HVX
 

README_cmake.md

@@ -392,7 +392,6 @@ apply when `WITH_TESTS=ON`:
 | `WITH_TEST_ERROR`         | `ON`    | enable the expected-error tests   |
 | `WITH_TEST_WARNING`       | `ON`    | enable the expected-warning tests |
 | `WITH_TEST_PERFORMANCE`   | `ON`    | enable performance testing        |
-| `WITH_TEST_OPENGL`        | `OFF`   | enable the OpenGL tests           |
 | `WITH_TEST_GENERATOR`     | `ON`    | enable the AOT generator tests    |
 
 The following options enable/disable various LLVM backends (they correspond to
@@ -416,7 +415,6 @@ The following options enable/disable various Halide-specific backends:
 | Option                | Default | Description                            |
 | --------------------- | ------- | -------------------------------------- |
 | `TARGET_OPENCL`       | `ON`    | Enable the OpenCL-C backend            |
-| `TARGET_OPENGL`       | `ON`    | Enable the OpenGL/GLSL backend         |
 | `TARGET_METAL`        | `ON`    | Enable the Metal backend               |
 | `TARGET_D3D12COMPUTE` | `ON`    | Enable the Direct3D 12 Compute backend |
 
@@ -466,6 +464,8 @@ If the CMake version is lower than 3.18, the deprecated [`FindCUDA`][findcuda]
 module will be used instead. It reads the variable `CUDA_TOOLKIT_ROOT_DIR`
 instead of `CUDAToolkit_ROOT` above.
 
+TODO: update this section for OpenGLCompute, which needs some (but maybe not all) of this.
+
 When targeting OpenGL, the [`FindOpenGL`][findopengl] and [`FindX11`][findx11]
 modules will be used to link AOT generated binaries. These modules can be
 overridden by setting the following variables:

apps/CMakeLists.txt

@@ -9,7 +9,6 @@ enable_testing()
 
 # add_subdirectory(HelloAndroid)  # TODO(#5374): missing CMake build
 # add_subdirectory(HelloAndroidCamera2)  # TODO(#5374): missing CMake build
-# add_subdirectory(HelloAndroidGL)  # TODO(#5374): missing CMake build
 # add_subdirectory(HelloMatlab)  # TODO(#5374): missing CMake build
 # add_subdirectory(HelloPyTorch)  # TODO(#5374): missing CMake build
 # add_subdirectory(HelloWasm)  # TODO(#5374): missing CMake build
@@ -24,7 +23,6 @@ add_subdirectory(conv_layer)
 add_subdirectory(cuda_mat_mul)
 add_subdirectory(depthwise_separable_conv)
 add_subdirectory(fft)
-add_subdirectory(glsl)
 add_subdirectory(harris)
 # add_subdirectory(hexagon_benchmarks)  # TODO(#5374): missing CMake build
 # add_subdirectory(hexagon_dma)  # TODO(#5374): missing CMake build
@@ -39,7 +37,6 @@ add_subdirectory(max_filter)
 add_subdirectory(nl_means)
 # add_subdirectory(nn_ops)  # TODO(#5374): missing CMake build
 # add_subdirectory(onnx)  # TODO(#5374): missing CMake build
-# add_subdirectory(opengl_demo)  # TODO(#5374): missing CMake build
 # add_subdirectory(openglcompute)  # TODO(#5374): missing CMake build
 add_subdirectory(resize)
 # add_subdirectory(resnet_50)  # TODO(#5374): missing CMake build