[all-commits] [llvm/llvm-project] 8d5c1b: [mlir][CRunnerUtils] Fix iterators accessing MemRe...

[Felix Schneider via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8d5c1b4562f880a61c9d9a2bddad73f584cdf311
      https://github.com/llvm/llvm-project/commit/8d5c1b4562f880a61c9d9a2bddad73f584cdf311
  Author: Felix Schneider <fx.schn at gmail.com>
  Date:   2023-09-14 (Thu, 14 Sep 2023)

  Changed paths:
    M mlir/include/mlir/ExecutionEngine/CRunnerUtils.h
    M mlir/unittests/ExecutionEngine/CMakeLists.txt
    M mlir/unittests/ExecutionEngine/DynamicMemRef.cpp
    A mlir/unittests/ExecutionEngine/StridedMemRef.cpp

  Log Message:
  -----------
  [mlir][CRunnerUtils] Fix iterators accessing MemRefs with non-zero offset

MemRef descriptors contain - among others - a field called `alignedPtr` or `data` and a field called `offset`. The actual buffer of the MemRef starts at `offset` elements after `alignedPtr`. In the CRunnerUtils, there exist helper classes to iterate over MemRefs' elements but the `offset` is not handled consistently so that accessing a MemRef with an `offset` != 0 via an iterator will lead to incorrect results.

The problem is that "offset" can be understood in two ways, firstly as the offset of the beginning of the MemRef with respect to the `alignedPtr`, ie what the `offset` field means in the MemRef descriptor, and secondly as the offset of some element within the MemRef relative to the first element of the MemRef, which could more accurately be called something like `linearIndex`.

The `offset` field within `StridedMemRefIterator` and `DynamicMemRefIterator` are interpreted the first way, therefore the offsets passed to the constructors of these classes need to account for the already existing offset in the descriptor on top of any potential "shift" within the MemRef.
This patch takes care of that and adds some basic tests that catch problems with indexing MemRefs with an `offset`.

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D157008