`getExprsBetween` is not getting expressions between vals

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Description

TEST_F(IterVisitorTest, ExprsBetween) {
  Fusion fusion;
  FusionGuard fg(&fusion);

  TensorView* tv0 = makeSymbolicTensor(1);
  TensorView* tv1 = set(tv0);
  TensorView* tv2 = set(tv1);
  TensorView* tv3 = set(tv2);
  TensorView* tv4 = set(tv3);

  fusion.addInput(tv0);
  fusion.addOutput(tv4);

  auto exprs0 = StmtSort::getExprsBetween({tv2}, {tv3});
  auto exprs1 = StmtSort::getExprsBetween({tv3}, {tv2});

  std::cout << "exprs0: " << ir_utils::toString(exprs0) << std::endl;
  std::cout << "exprs1: " << ir_utils::toString(exprs1) << std::endl;

  EXPECT_EQ(exprs0, std::vector<Expr*>{tv3->definition()});
  EXPECT_EQ(exprs1, std::vector<Expr*>{});
}

exprs1:
T1_l[ iS1{i0} ]
   = Set( T0_g[ iS0{i0} ], cache_op=Streaming )
T2_l[ iS2{i0} ]
   = Set( T1_l[ iS1{i0} ], cache_op=Streaming )

Contributor guide

Research direction

Investigate the implementation of StmtSort::getExprsBetween to understand why it returns expressions when the second set of expressions is not downstream of the first set. The test expects that getExprsBetween({tv3}, {tv2}) returns an empty vector because tv3 depends on tv2, meaning expressions from tv2 to tv3 are not between tv3 and tv2 (since tv3 is after tv2 in the forward direction). Check the traversal order and ensure that only expressions that are on a path from the 'from' nodes to the 'to' nodes are returned, not the reverse.

Tech stack

cpp

Domain

backend

Issue type

Bug

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

2

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

1-3 hours

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

Active

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

Clear

Prerequisites

C++Git

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

60