Bug 1730014 - Avoid ASCII intermediate for WGSL shader code r=jgilbert,webidl,emilio

we were doing UTF16 -> ASCII null term -> UTF8, and we were losing information on the way.
Now we go UTF16 -> UTF8 -> UTF8 null term
Also, we no longer accept SPIR-V

Differential Revision: https://phabricator.services.mozilla.com/D125123

dom/webgpu/Buffer.cpp

@@ -11,6 +11,7 @@
 #include "mozilla/HoldDropJSObjects.h"
 #include "mozilla/ipc/Shmem.h"
 #include "ipc/WebGPUChild.h"
+#include "js/ArrayBuffer.h"
 #include "js/RootingAPI.h"
 #include "nsContentUtils.h"
 #include "nsWrapperCache.h"

dom/webgpu/ipc/WebGPUChild.cpp

@@ -603,16 +603,8 @@ RawId WebGPUChild::DeviceCreateShaderModule(
     RawId aSelfId, const dom::GPUShaderModuleDescriptor& aDesc) {
   ffi::WGPUShaderModuleDescriptor desc = {};
 
-  nsCString wgsl;
-  if (aDesc.mCode.IsUSVString()) {
-    LossyCopyUTF16toASCII(aDesc.mCode.GetAsUSVString(), wgsl);
-    desc.wgsl_chars = wgsl.get();
-  } else {
-    const auto& code = aDesc.mCode.GetAsUint32Array();
-    code.ComputeState();
-    desc.spirv_words = code.Data();
-    desc.spirv_words_length = code.Length();
-  }
+  desc.code = reinterpret_cast<const uint8_t*>(aDesc.mCode.get());
+  desc.code_length = aDesc.mCode.Length();
 
   ByteBuf bb;
   RawId id = ffi::wgpu_client_create_shader_module(mClient, aSelfId, &desc,

dom/webidl/WebGPU.webidl

@@ -612,11 +612,10 @@ interface GPUCompilationInfo {
 };
 
 // ShaderModule
-//TODO: remove the `Uint32Array` variant, it's used for SPIR-V
-typedef (Uint32Array or USVString) GPUShaderCode;
 
 dictionary GPUShaderModuleDescriptor : GPUObjectDescriptorBase {
-    required GPUShaderCode code;
+    // UTF8String is not observably different from USVString
+    required UTF8String code;
     object sourceMap;
 };
 

gfx/wgpu_bindings/src/client.rs

@@ -38,9 +38,8 @@ fn make_byte_buf<T: serde::Serialize>(data: &T) -> ByteBuf {
 #[repr(C)]
 pub struct ShaderModuleDescriptor {
     label: RawString,
-    spirv_words: *const u32,
-    spirv_words_length: usize,
-    wgsl_chars: RawString,
+    code: *const u8,
+    code_length: usize,
 }
 
 #[repr(C)]
@@ -913,12 +912,13 @@ pub unsafe extern "C" fn wgpu_client_create_shader_module(
         .shader_modules
         .alloc(backend);
 
-    let code = cow_label(&desc.wgsl_chars).unwrap_or_default();
+    let code =
+        std::str::from_utf8_unchecked(std::slice::from_raw_parts(desc.code, desc.code_length));
     let desc = wgc::pipeline::ShaderModuleDescriptor {
         label: cow_label(&desc.label),
     };
 
-    let action = DeviceAction::CreateShaderModule(id, desc, code);
+    let action = DeviceAction::CreateShaderModule(id, desc, Cow::Borrowed(code));
     *bb = make_byte_buf(&action);
     id
 }