Improve find_permutation with ambiguous layouts

[pfultz2]

Motivation

When using find_permutation(std::vector<shape>), it pick the permutation that most shapes uses. However, with an ambiguous layout(such as shapes with dimensions of 1) a better choice can be found by considering what other layouts are compatible.

Technical Details

Changelog Category

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• • Added: New functionality.
• • Changed: Changes to existing functionality.
• • Removed: Functionality or support that has been removed. (Compared to a previous release)
• • Optimized: Component performance that has been optimized or improved.
• • Resolved Issues: Known issues from a previous version that have been resolved.
• • Not Applicable: This PR is not to be included in the changelog.

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[Copilot]

Pull request overview

This PR improves MIGraphX’s find_permutation(std::vector<shape>) layout selection when some shapes are layout-ambiguous due to singleton dimensions, so that “definite” layouts can win even when ambiguous shapes are present. It also introduces a small output-iterator utility to enable in-place algorithm updates of tuple/pair elements (used to update std::map values), alongside new tests covering the updated behavior.

Changes:

• Update find_permutation(std::vector<shape>) to vote based on which candidate permutations each shape can support (treating singleton dims as layout-ambiguous).
• Add function_output_iterator_adaptor and element_output_iterator<N> to support algorithmic updates of container element subfields (e.g., map values).
• Add/extend unit tests for ambiguous-layout permutation selection and a concat/layout-convolution scenario.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/permutation.cpp	Updates multi-shape permutation selection to account for singleton-dim ambiguity via “supported permutation” voting.
src/include/migraphx/output_iterator.hpp	Adds output-iterator adaptor utilities used to update map values via standard algorithms.
test/shape_test.cpp	Adds new test cases for ambiguous singleton-dimension layout selection in find_permutation(vector<shape>).
test/op_shape_test.cpp	Adds concat shape test ensuring NHWC wins when the other input is singleton-channel ambiguous.
test/layout_convolution.cpp	Adds regression test ensuring concat with singleton-channel literal doesn’t force an unwanted relayout under channels-last convolution pass.
test/output_iterator_test.cpp	Adds unit tests for the new output-iterator utilities.

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[codecov]

Codecov Report

❌ Patch coverage is 94.11765% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/permutation.cpp	91.67%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5153      +/-   ##
===========================================
+ Coverage    93.12%   93.13%   +0.01%     
===========================================
  Files          625      625              
  Lines        33162    33282     +120     
===========================================
+ Hits         30879    30995     +116     
- Misses        2283     2287       +4     

Files with missing lines	Coverage Δ
src/include/migraphx/output_iterator.hpp	100.00% <100.00%> (ø)
src/permutation.cpp	85.19% <91.67%> (+1.58%)	⬆️

... and 3 files with indirect coverage changes

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