clear residual op in vpto emit

[Likai-19]

问题总结

VPTO lowering pipeline 完成后，module 中残留的 tile 元数据 op 阻塞了 LLVM 导出。这些 op 分为两类：

1. 语义已完成但未清理的死 op：pto.set_valid_shape（始终无 user）、无 user 的 pto.get_valid_shape、无 user 的 pto.treshape、无 user 的 pto.alloc_tile、无 user 的 UnrealizedConversionCastOp。

2. 可被折叠的 cast 链：pto.get_valid_shape → UnrealizedConversionCastOp → LLVM i64 的 cast 链，其等价的 LLVM i64 值已存在于原始 pto.alloc_tile 的 valid row/col 属性中，但未被复用。

[gemini-code-assist]

Code Review

This pull request introduces folding for pto.get_validshape intrinsics into materialized tile handles, along with erasing unused pto.set_validshape operations and performing dead code elimination (DCE) on leftover tile-handle view and allocation operations. The review feedback suggests optimizing the iterative DCE implementation to a worklist-based approach to improve complexity from $O(N \times M)$ to $O(N + M)$, and adding a safety check to ensure UnrealizedConversionCastOp has exactly one result before accessing it.

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[gemini-code-assist]

The current iterative DCE implementation performs a full function walk (func.walk) inside a while loop for every level of dead tile operations. For a chain of $N$ dead operations, this results in $O(N \times M)$ complexity (where $M$ is the number of operations in the function).

We can optimize this to $O(N + M)$ by using a worklist-based approach. When an operation is erased, we check if its operands have become dead and add them to the worklist if they match the target types. Additionally, we should verify that UnrealizedConversionCastOp has exactly 1 result before accessing getResult(0) to prevent potential out-of-bounds assertions.

    SmallVector<Operation *, 8> worklist;
    func.walk([&](Operation *op) {
      if (!op->use_empty())
        return;
      if (isa<pto::TReshapeOp, pto::MaterializeTileOp, pto::AllocTileOp>(op)) {
        worklist.push_back(op);
      } else if (auto castOp = dyn_cast<UnrealizedConversionCastOp>(op)) {
        if (castOp.getNumOperands() == 1 && castOp.getNumResults() == 1 &&
            isa<pto::TileBufType>(castOp.getResult(0).getType()))
          worklist.push_back(op);
      }
    });

    while (!worklist.empty()) {
      Operation *op = worklist.pop_back_val();
      SmallVector<Value, 4> operands(op->getOperands());
      op->erase();
      for (Value operand : operands) {
        if (auto *defOp = operand.getDefiningOp()) {
          if (!defOp->use_empty())
            continue;
          if (isa<pto::TReshapeOp, pto::MaterializeTileOp, pto::AllocTileOp>(defOp)) {
            worklist.push_back(defOp);
          } else if (auto castOp = dyn_cast<UnrealizedConversionCastOp>(defOp)) {
            if (castOp.getNumOperands() == 1 && castOp.getNumResults() == 1 &&
                isa<pto::TileBufType>(castOp.getResult(0).getType()))
              worklist.push_back(defOp);
          }
        }
      }
    }

[reedhecre]

Codex Review

该评论由 review 机器人自动更新。

• PR: clear residual op in vpto emit #855 clear residual op in vpto emit
• Author: Likai-19
• Base/Head: main / vpto_clear_residual_op
• Head SHA: eb6e8d3849d1
• Trigger: 检测到新的 open PR
• Generated At: 2026-06-23T07:12:01Z
• Status: completed

Summary

PR 在两阶段 FoldTileBufIntrinsics 流水线里过早删除 set_validshape，会导致后续 valid-shape 读取/折叠看到错误的元数据。

Findings

1. P2 `shape-only` now drops `set_validshape` before later valid-shape readers are folded lib/PTO/Transforms/FoldTileBufIntrinsics.cpp:729

VPTO pipeline runs this pass twice: shape-only first and addr-only later (tools/ptoas.cpp:1494-1509). The new cleanup here erases every pto.set_validshape in the first pass, but the newly added pto.get_validshape folding only happens in the addr-family block above. That means any later get_validshape/treshape-derived reader in the second pass no longer sees the override and folds back to the original alloc/materialize valid dims. This breaks the dynamic-valid treshape + set_validshape patterns produced by PTOA5NormalizeTMovPass, and it also makes --fold-mode=shape-only itself non-semantics-preserving for IR that still contains get_validshape.