# MLIR gains static memory planner to eliminate heap allocations

> **Key takeaway:** A Google Summer of Code 2026 project merged into LLVM's MLIR replaces multiple heap allocations with a single compile-time-sized arena, targeting embedded CPUs, DSPs, and custom accelerators where dynamic allocation is prohibited or expensive.

**Published:** 2026-10-19T00:00:00+00:00 
**Source:** LLVM Compiler Infrastructure 
**Category:** kernel-os 
**Canonical URL:** https://fosswire.org/news/mlir-gains-static-memory-planner-to-eliminate-heap-allocatio.html 

## Summary
Krish Gupta's GSoC 2026 work under the LLVM Foundation introduced a static-memory-planner pass for MLIR that coalesces memref.alloc operations into a single memref<Nxi8> arena with memref.view slices. The pass uses BufferViewFlowAnalysis to track buffer lifetimes through control flow including arith.select, scf.if, scf.for, and cf branches. Two allocation algorithms are available: trivial sequential packing and a best-fit planner that reuses arena space for non-overlapping lifetimes. The feature landed across three upstream PRs (#205125, #209106, #213634) between June and August 2026.

## How the planner transforms MLIR bufferization
- **Six-step pipeline**: collect candidates via alias analysis, build (size, alignment, timeStart, timeEnd) descriptors in O(n+m), run planner algorithm, assign byte offsets, create single arena allocation, rewrite allocs to views and erase deallocs
- **Two arena modes**: `allocate` creates the arena inside the function; `arg` receives it as a function parameter for external memory management
- **Two planner algorithms**: `trivialMemoryPlanner` for sequential packing; `bestFitMemoryPlanner` for lifetime-aware slot reuse
- **BufferViewFlowAnalysis integration**: unified alias analysis replacing hand-rolled DFS, handling arith.select, scf.if/scf.for results, cf branches, and view ops through BufferViewFlowOpInterface, RegionBranchOpInterface, BranchOpInterface, and ViewLikeOpInterface
- **Reverse-alias safety guard**: prevents dealloc erasure when a dealloc may free both arena-managed and non-arena-managed allocations, using resolveReverse() to trace all possible source allocs
- **Lifetime anchoring**: deallocs nested in scf.if bodies use findAncestorOpInBlock to conservatively extend timeEnd to the enclosing op's block index

## Why it matters
The pass directly benefits downstream MLIR-based compiler pipelines targeting edge and accelerator deployments where heap allocation is unavailable or performance-prohibitive, including TensorFlow Lite, IREE, and custom DSP toolchains.