Remove separate NCNN_WEBGPU option, enable automatically with emscripten + vulkan

Co-authored-by: nihui <171016+nihui@users.noreply.github.com>

CMakeLists.txt

@@ -77,7 +77,6 @@ option(NCNN_PIXEL_AFFINE "warp affine image pixel" ON)
 option(NCNN_PIXEL_DRAWING "draw basic figure and text" ON)
 option(NCNN_CMAKE_VERBOSE "print verbose cmake messages" OFF)
 option(NCNN_VULKAN "vulkan compute support" OFF)
-option(NCNN_WEBGPU "webgpu compute support" OFF)
 option(NCNN_SIMPLEVK "minimal in-house vulkan loader" ON)
 option(NCNN_SYSTEM_GLSLANG "use system glslang library" OFF)
 option(NCNN_RUNTIME_CPU "runtime dispatch cpu routines" ON)
@@ -832,16 +831,9 @@ if(NCNN_VULKAN)
     endif()
 endif()
 
-if(NCNN_WEBGPU)
-    # WebGPU native support reuses Vulkan shader compilation infrastructure
-    # but requires different runtime and uniform handling
-    message(STATUS "WebGPU native support enabled")
-    
-    # Enable Vulkan infrastructure for shader compilation if not already enabled
-    if(NOT NCNN_VULKAN)
-        message(STATUS "Enabling Vulkan infrastructure for WebGPU shader compilation")
-        set(NCNN_VULKAN ON)
-    endif()
+# Automatically enable WebGPU when compiling to wasm target with emscripten if Vulkan is enabled
+if(CMAKE_SYSTEM_NAME STREQUAL "Emscripten" AND NCNN_VULKAN)
+    message(STATUS "WebGPU native support enabled (emscripten + vulkan)")
     
     # WebGPU specific configuration flags
     add_definitions(-DNCNN_WEBGPU=1)

cmake/ncnn_add_shader.cmake

@@ -3,7 +3,7 @@ macro(ncnn_add_shader NCNN_SHADER_SRC)
     get_filename_component(NCNN_SHADER_SRC_NAME_WE ${NCNN_SHADER_SRC} NAME_WE)
     set(NCNN_SHADER_COMP_HEADER ${CMAKE_CURRENT_BINARY_DIR}/layer/vulkan/shader/${NCNN_SHADER_SRC_NAME_WE}.comp.hex.h)
 
-    if(NCNN_WEBGPU)
+    if(CMAKE_SYSTEM_NAME STREQUAL "Emscripten" AND NCNN_VULKAN)
         # Use WebGPU shader transformation for push constant -> uniform binding conversion
         add_custom_command(
             OUTPUT ${NCNN_SHADER_COMP_HEADER}

docs/webgpu-implementation-summary.md

@@ -21,14 +21,14 @@ The original issue identified two critical problems when trying to compile Vulka
 ### 1. Build System Changes
 
 **CMakeLists.txt**:
-- Added `NCNN_WEBGPU` option
-- Automatically enables Vulkan infrastructure when WebGPU is enabled
+- Automatic WebGPU detection when targeting emscripten with Vulkan enabled  
+- Uses `CMAKE_SYSTEM_NAME STREQUAL "Emscripten" AND NCNN_VULKAN` condition
 - Sets `NCNN_WEBGPU=1` preprocessor define
 
 ### 2. Shader Preprocessing Pipeline
 
 **cmake/ncnn_add_shader.cmake**:
-- Added conditional logic to use WebGPU shader transformation when `NCNN_WEBGPU=ON`
+- Added conditional logic to use WebGPU shader transformation when targeting emscripten + vulkan
 - Uses `ncnn_generate_webgpu_shader_header.cmake` for transformation
 
 **cmake/ncnn_generate_webgpu_shader_header.cmake**:
@@ -72,9 +72,9 @@ if (gx >= psc(w)) return;  // psc(w) = (float(w)==0?p.w:w)
 ## Usage
 
 ```bash
-# Enable WebGPU native support
-cmake .. -DNCNN_WEBGPU=ON
-make -j$(nproc)
+# Enable WebGPU native support with emscripten
+emcmake cmake .. -DNCNN_VULKAN=ON
+emmake make -j$(nproc)
 ```
 
 This implementation provides a solid foundation for WebGPU native support while maintaining compatibility with existing Vulkan infrastructure.

docs/webgpu-native-support.md

@@ -10,15 +10,16 @@ This implementation adds WebGPU native support to NCNN, allowing the reuse of ex
 
 ## Usage
 
-Enable WebGPU support by adding `-DNCNN_WEBGPU=ON` to your CMake configuration:
+WebGPU support is automatically enabled when compiling to WebAssembly (wasm) target with emscripten and Vulkan support is enabled:
 
 ```bash
-cmake .. -DNCNN_WEBGPU=ON
+# Use emscripten toolchain with Vulkan enabled
+emcmake cmake .. -DNCNN_VULKAN=ON
 ```
 
 This will automatically:
-- Enable Vulkan infrastructure for shader compilation
-- Transform all ~300+ compute shaders for WebGPU compatibility
+- Enable WebGPU when targeting emscripten + vulkan
+- Transform all ~300+ compute shaders for WebGPU compatibility  
 - Apply the correct psc macro definition
 
 ## Shader Transformation Example
@@ -57,7 +58,7 @@ The implementation addresses the SPIR-V compilation issues mentioned in the GitH
 
 ## Files Modified
 
-- `CMakeLists.txt`: Added NCNN_WEBGPU option
+- `CMakeLists.txt`: Automatic WebGPU detection for emscripten + vulkan
 - `src/gpu.cpp`: Updated psc macro for WebGPU compatibility
 - `cmake/ncnn_add_shader.cmake`: Added WebGPU shader preprocessing path
 - `cmake/ncnn_generate_webgpu_shader_header.cmake`: New shader transformation logic
@@ -65,10 +66,10 @@ The implementation addresses the SPIR-V compilation issues mentioned in the GitH
 ## Building
 
 ```bash
-# Standard build with WebGPU support
+# Standard build with WebGPU support using emscripten
 mkdir build && cd build
-cmake .. -DNCNN_WEBGPU=ON -DNCNN_BUILD_TESTS=ON
-make -j$(nproc)
+emcmake cmake .. -DNCNN_VULKAN=ON -DNCNN_BUILD_TESTS=ON
+emmake make -j$(nproc)
 ```
 
-All 300+ compute shaders will be automatically transformed during the build process.
+All 300+ compute shaders will be automatically transformed during the build process when targeting emscripten with vulkan enabled.