diff --git a/mlir/include/mlir/Dialect/LLVMIR/NVVMOps.td b/mlir/include/mlir/Dialect/LLVMIR/NVVMOps.td index 1cc5b74a3cb67..d25e51e96ed8e 100644 --- a/mlir/include/mlir/Dialect/LLVMIR/NVVMOps.td +++ b/mlir/include/mlir/Dialect/LLVMIR/NVVMOps.td @@ -79,6 +79,40 @@ def NVVM_Dialect : Dialect { sequence must be expressed directly, NVVM provides an `nvvm.inline_ptx` op to embed PTX inline as a last-resort escape hatch, with explicit operands and results. + + + **Memory Spaces:** The NVVM dialect introduces the following memory spaces, + each with distinct scopes and lifetimes: +``` + | Memory Space | Address Space | Scope | Lifetime | + |-------------------|---------------|----------------------|-------------------| + | `generic` | 0 | All threads | Context-dependent | + | `global` | 1 | All threads (device) | Application | + | `shared` | 3 | Thread block (CTA) | Kernel execution | + | `constant` | 4 | All threads (RO) | Application | + | `local` | 5 | Single thread | Kernel execution | + | `tensor` | 6 | Thread block (CTA) | Kernel execution | + | `shared_cluster` | 7 | Thread block cluster | Kernel execution | +``` + **Memory Space Details:** + - **generic**: Can point to any memory space; requires runtime resolution of + actual address space. Use when pointer origin is unknown at compile time. + Performance varies based on the underlying memory space. + - **global**: Accessible by all threads across all blocks; persists across + kernel launches. Highest latency but largest capacity (device memory). Best + for large data and inter-kernel communication. + - **shared**: Shared within a thread block (CTA); very fast on-chip memory for + cooperation between threads in the same block. Limited capacity. Ideal for + block-level collaboration, caching, and reducing global memory traffic. + - **constant**: Read-only memory cached per SM. Size typically limited to + 64KB. Best for read-only data and uniform values accessed by all threads. + - **local**: Private to each thread. Use for per-thread private data and + automatic variables that don't fit in registers. + - **tensor**: Special memory space for tensor core operations. Used by + `tcgen05` instructions on SM 100+ for tensor input/output operations. + - **shared_cluster**: Distributed shared memory across thread blocks within + a cluster (SM 90+). Enables collaboration beyond single-block scope with + fast access across cluster threads. }]; let name = "nvvm";