gfx-rs/wgpu · error

not implemented

Error message

not implemented

What it means

Panic in naga's SPIR-V subgroup-operation writer: after requiring GroupNonUniform capability, the result type turned out to be something other than a scalar or the expected vector shape, hitting an unimplemented match arm. The faulty input is the subgroup expression's result type.

Source

Thrown at naga/src/back/spv/subgroup.rs:67

                )?;
            }
            _ => {
                self.writer.require_any(
                    "GroupNonUniformArithmetic",
                    &[spirv::Capability::GroupNonUniformArithmetic],
                )?;
            }
        }

        let id = self.gen_id();
        let result_ty = &self.fun_info[result].ty;
        let result_type_id = self.get_expression_type_id(result_ty);
        let result_ty_inner = result_ty.inner_with(&self.ir_module.types);

        let (is_scalar, scalar) = match *result_ty_inner {
            TypeInner::Scalar(kind) => (true, kind),
            TypeInner::Vector { scalar: kind, .. } => (false, kind),
            _ => unimplemented!(),
        };

        use crate::ScalarKind as sk;
        let spirv_op = match (scalar.kind, *op) {
            (sk::Bool, sg::All) if is_scalar => spirv::Op::GroupNonUniformAll,
            (sk::Bool, sg::Any) if is_scalar => spirv::Op::GroupNonUniformAny,
            (_, sg::All | sg::Any) => unimplemented!(),

            (sk::Sint | sk::Uint, sg::Add) => spirv::Op::GroupNonUniformIAdd,
            (sk::Float, sg::Add) => spirv::Op::GroupNonUniformFAdd,
            (sk::Sint | sk::Uint, sg::Mul) => spirv::Op::GroupNonUniformIMul,
            (sk::Float, sg::Mul) => spirv::Op::GroupNonUniformFMul,
            (sk::Sint, sg::Max) => spirv::Op::GroupNonUniformSMax,
            (sk::Uint, sg::Max) => spirv::Op::GroupNonUniformUMax,
            (sk::Float, sg::Max) => spirv::Op::GroupNonUniformFMax,
            (sk::Sint, sg::Min) => spirv::Op::GroupNonUniformSMin,
            (sk::Uint, sg::Min) => spirv::Op::GroupNonUniformUMin,
            (sk::Float, sg::Min) => spirv::Op::GroupNonUniformFMin,

View on GitHub (pinned to 3e11ff59bf)

Solutions

1. Use subgroup built-ins with scalar or vecN<u32/i32/f32> result types
2. Extend the writer match to cover the needed type if this is a legitimate naga gap

When it happens

Trigger: Thrown at naga/src/back/spv/subgroup.rs:67 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of gfx-rs/wgpu@3e11ff59bf (2026-09-03). Data as JSON: /api/errors/2e371eee1d23d18b. Report an issue: GitHub.