Uniform (Read-Only) Load Memory

Load a value from memory that is known to be identical across all threads/lanes in the group, via the scalar/uniform data path.

Vendor-Neutral Definition

d = *addr, issued once per wavefront/warp on the scalar path rather than once per lane on the vector path, since the loaded value is guaranteed uniform.
⚠️ Cross-vendor mappings describe semantic relationships and are not guaranteed one-to-one compiler translations.
equivalent with restrictions Both load a value known to be uniform across the thread group through a dedicated scalar/read-only data path rather than the general per-lane path.
Property NVIDIA PTX AMDGPU
Instruction ldu s_load_dword
ISA Layer Virtual Native
Data Types - -
Version / Target Introduced PTX ISA 2.0 gfx942/gfx1100

Important Differences

  • PTX's ldu is a per-thread instruction carrying an explicit compiler promise that the loaded value happens to be uniform; AMDGPU's s_load_dword is inherently scalar (issued once per wavefront, result placed in an SGPR shared by all lanes) - the uniformity is architectural on AMDGPU rather than an optional hint on an otherwise-per-lane instruction.

Source Evidence

Verification method: documentation