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Data Type Support by Backend

Tracks verified support for all data types across all 7 backends. Updated: 2026-04-13

Legend:

  • PASS - verified with unit tests (real data, real kernels, real verification)
  • FAIL - tests exist, currently failing
  • [!] KNOWN LIMITATION - architectural constraint, not a bug
  • [-] NOT TESTED - no tests yet, status unknown
  • [N/A] - not applicable to this backend

Buffer Read (Load from ArrayView)

Type C# Type Size WebGPU WebGPU NoSub Wasm WebGL CUDA OpenCL CPU
Int8 sbyte 1B [x] [x] [x] [x] [x] [x] [x]
UInt8 byte 1B [x] [x] [x] [x] [x] [x] [x]
Int16 short 2B [x] [x] [x] [x] [x] [x] [x]
UInt16 ushort 2B [x] [x] [x] [x] [x] [x] [x]
Int32 int 4B [x] [x] [x] [x] [x] [x] [x]
UInt32 uint 4B [x] [x] [x] [x] [x] [x] [x]
Int64 long 8B [x] [x] [x] [x] [x] [x] [x]
UInt64 ulong 8B [x] [x] [x] [x] [x] [x] [x]
Float16 Half 2B [x] [x] [x] [x] [x] [x] [x]
Float32 float 4B [x] [x] [x] [x] [x] [x] [x]
Float64 double 8B [x] [x] [x] [x] [x] [x] [x]

Buffer Write (Store to ArrayView)

Type C# Type Size WebGPU WebGPU NoSub Wasm WebGL CUDA OpenCL CPU
Int8 sbyte 1B [x] [x] [x] [x] [x] [x] [x]
UInt8 byte 1B [x] [x] [x] [x] [x] [x] [x]
Int16 short 2B [x] [x] [x] [x] [x] [x] [x]
UInt16 ushort 2B [x] [x] [x] [x] [x] [x] [x]
Int32 int 4B [x] [x] [x] [x] [x] [x] [x]
UInt32 uint 4B [x] [x] [x] [x] [x] [x] [x]
Int64 long 8B [x] [x] [x] [x] [x] [x] [x]
UInt64 ulong 8B [x] [x] [x] [x] [x] [x] [x]
Float16 Half 2B [x] [x] [x] [x] [x] [x] [x]
Float32 float 4B [x] [x] [x] [x] [x] [x] [x]
Float64 double 8B [x] [x] [x] [x] [x] [x] [x]

End-to-End (Read + Kernel Process + Write)

Type C# Type Size WebGPU WebGPU NoSub Wasm WebGL CUDA OpenCL CPU
Int8 sbyte 1B [x] [x] [x] [x] [x] [x] [x]
UInt8 byte 1B [x] [x] [x] [x] [x] [x] [x]
Int16 short 2B [x] [x] [x] [x] [x] [x] [x]
UInt16 ushort 2B [x] [x] [x] [x] [x] [x] [x]
Int32 int 4B [x] [x] [x] [x] [x] [x] [x]
UInt32 uint 4B [x] [x] [x] [x] [x] [x] [x]
Int64 long 8B [x] [x] [x] [x] [x] [x] [x]
UInt64 ulong 8B [x] [x] [x] [x] [x] [x] [x]
Float16 Half 2B [x] [x] [x] [x] [x] [x] [x]
Float32 float 4B [x] [x] [x] [x] [x] [x] [x]
Float64 double 8B [x] [x] [x] [x] [x] [x] [x]

Buffer RoundTrip (CopyFromCPU -> CopyToHostAsync, no kernel)

Type C# Type Size WebGPU WebGPU NoSub Wasm WebGL CUDA OpenCL CPU
Int8 sbyte 1B [x] [x] [x] [x] [x] [x] [x]
UInt8 byte 1B [x] [x] [x] [x] [x] [x] [x]
Int16 short 2B [x] [x] [x] [x] [x] [x] [x]
UInt16 ushort 2B [x] [x] [x] [x] [x] [x] [x]
Float16 Half 2B [-] [-] [-] [-] [-] [-] [-]

Half Math Intrinsics

Function WebGPU WebGPU NoSub Wasm WebGL CUDA OpenCL CPU
Abs [x] [x] [x] [x] [x] [x] [x]
Min/Max [x] [x] [x] [x] [x] [x] [x]
Clamp [-] [-] [-] [-] [-] [-] [-]

CopyFromJS (Browser-only: JS TypedArray/ArrayBuffer -> GPU)

Type C# Type Size WebGPU Wasm WebGL
Int32 int 4B [x] [x] [x]
Float32 float 4B [x] [x] [x]

Atomic Operations

See Docs/atomic-operations.md for the complete per-operation support matrix.

Type C# Type WebGPU Wasm WebGL CUDA OpenCL CPU
Int32 int [x] [x] [!] Add only (vote TF) [x] [x] [x]
UInt32 uint [x] [x] [!] Add only (vote TF) [x] [x] [x]
Int64 long [x] Add/bitwise, [!] Min/Max/Exch/CAS [x] [!] [x] [x] [x]
UInt64 ulong [x] Add/bitwise, [!] Min/Max/Exch/CAS [x] [!] [x] [x] [x]
Float32 float [x] CAS loop [x] CAS loop [!] [x] [x] [x]
Float64 double [!] [x] CAS loop [!] [x] [x] [x]

[!] = Throws NotSupportedException at kernel compilation time. See atomic-operations.md for details.

Implementation Summary

Sub-word buffer access (Int8, UInt8, Int16, UInt16, Float16)

All sub-word types now have complete Read/Write/EndToEnd support on ALL 7 backends.

Backend Mechanism Signed/Unsigned Detection
WebGPU array<atomic<u32>> + atomicAnd/atomicOr for Store, atomicLoad for Read. IEEE 754 f16<->f32 inline conversion for Float16. EntryPoint.Parameters[N].GetGenericArguments()[0] CLR type check
Wasm Native i32.load8_s/u, i32.load16_s/u, i32.store8, i32.store16 opcodes. Float16 via EmitF16ToF32/EmitF32ToF16. CLR type trace via _generatorArgs.EntryPoint.Parameters
WebGL texelFetch from R32I texture, shift+mask extraction. TF output with sub-word packing in glWorker.js. Float16 via GLSL f16<->f32 bit manipulation. EntryPoint.Parameters[N] CLR type check
OpenCL Native types for Int8/UInt8/Int16/UInt16. Float16 via vload_half/vstore_half with tracked LEA base pointer. Native type support
CPU/CUDA Native sub-word support, no special handling needed. Native

Sub-Word Usage Notes

These apply to any kernel using ArrayView<byte>, ArrayView<sbyte>, ArrayView<short>, ArrayView<ushort>, or ArrayView<Half>:

  • Use ILGPU.Half, NOT System.Half, in kernel signatures. Implicit conversion operators are defined for interop, so you can mix the two on the host side; inside the kernel signature the ILGPU.Half type is what the IR + codegen expect.
  • Sub-word writes on WebGPU lower to atomic RMW. Two threads writing different halves of the same u32 word would race without RMW; the codegen always synthesizes atomicAnd mask + atomicOr set so the writes are thread-safe. Setting RequiresAtomics = true in AcceleratorRequirements (or pinning to a backend with atomics) is therefore mandatory whenever a kernel writes a sub-word view — WebGL has no atomics and rejects sub-word writes at compile time. See capabilities-and-backend-selection.md.
  • Sub-word view reads can return stale data on WebGPU if you wrote to the same slot in the same kernel invocation. Byte writes lower to atomic RMW on WebGPU; reading a byte slot you just wrote may observe pre-RMW state in the same dispatch. Treat ArrayView<byte> and ArrayView<sbyte> as write-only within a kernel invocation — buffer the value in a register and route results through that register, not back through the view.
  • arrayLength() on sub-word buffers returns the u32-count, not the element-count. A 256-byte buffer reports arrayLength = 64 (256/4 u32s). Multiply by elements-per-word (4 for byte/sbyte, 2 for short/ushort/Half) when computing element bounds inside the kernel.
  • Sign extension on load is automatic. ArrayView<sbyte> and ArrayView<short> reads sign-extend the narrow value to int when used in arithmetic. The codegen emits extractBits(x, 0u, 16u) (WGSL) / int(int16_t(x)) (GLSL) / i32.load16_s (Wasm).
  • Wasm minimum buffer size is 4 bytes. Allocating an ArrayView<byte> of length 1, 2, or 3 throws Invalid typed array length: 4 on Wasm. Pad per-block scalar buffers to Math.Max(blockCount, 4L) if your kernel writes one byte per block.

Test Coverage

147 tests total across 10 sub-word test methods x 7 backends + Half intrinsics:

  • Int8: 28 tests (RoundTrip + Read + Write + EndToEnd x 7 backends)
  • UInt8: 28 tests
  • Int16: 35 tests (+ existing CopyFromJS tests)
  • UInt16: 28 tests
  • Float16: 21 tests (Read + Write + EndToEnd x 7 backends)
  • Half Abs: 7 tests
  • Half MinMax: 7 tests

Test File

SpawnDev.ILGPU.Demo.Shared/UnitTests/BackendTestBase.Tests17.BrowserBuffer.cs

How to Run

# All sub-word tests
dotnet test PlaywrightMultiTest/PlaywrightMultiTest.csproj --filter "FullyQualifiedName~Int8|FullyQualifiedName~UInt8|FullyQualifiedName~Int16|FullyQualifiedName~UInt16|FullyQualifiedName~Float16|FullyQualifiedName~Half_"