Remove IterType::gatherscatter

[naoyam]

Just cleaning up an obsolete IterType. Nothing should depend on IterType::GatherScatter anymore.

[naoyam]

!test --diff

[github-actions]

Description

• Removed unnecessary IterType::GatherScatter usage

• Simplified IterDomainBuilder in gather function

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Changes walkthrough 📝

	Relevant files
Enhancement	indexing.cpp Simplify IterDomainBuilder usage                                                  csrc/ops/indexing.cpp Removed IterType::GatherScatter assignment in IterDomainBuilder Simplified out_domain construction in gather function +1/-7

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PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🧪 No relevant tests

⚡ Recommended focus areas for review Performance Impact The change removes the specific IterType::GatherScatter setting for IterDomain. This might affect the performance of gather operations, especially if GatherScatter was used for optimization purposes. out_domain.push_back(IterDomainBuilder(idx_domain_ptr).build());

[naoyam]

!test --diff

[naoyam]

!test --diff

[greptile-apps]

Greptile Summary

This PR removes IterType::GatherScatter from the codebase, a special iter-type previously assigned to the output domains of gather and scatter operations. Gather/scatter outputs now use the regular IterType::Iteration, the contiguity logic that was guarded by the GatherScatter special-case is removed, and all related assertions and helper methods (isGatherScatter()) are cleaned up. The diff also bundles several unrelated hygiene improvements: std::ranges algorithms, std::uint8_t underlying types on several enums, named aggregate-initializer syntax, and minor data_type_to_aten consolidations.

Confidence Score: 5/5

Safe to merge — all GatherScatter references are consistently removed and no functional regressions are apparent.

The removal is complete and internally consistent: the enum value, helper predicate, contiguity guards, merge logic, validation checks, and the corresponding test are all updated in lock-step. The data_type_to_aten fallback simplification is functionally identical (8-bit types without explicit switch cases still reach the else-Byte branch). No P0 or P1 issues found.

No files require special attention.

Important Files Changed

Filename	Overview
csrc/type.h	Removes IterType::GatherScatter from the enum and adds std::uint8_t underlying type to IterType and many other enums.
csrc/type.cpp	Removes iter_type2string case for GatherScatter; consolidates data_type_to_aten 8-bit fallback into the else branch (functionally identical); minor named-initializer and max_digits10 cleanups.
csrc/ir/internal_base_nodes.h	Removes the isGatherScatter() convenience predicate from IterDomain.
csrc/ir/internal_base_nodes.cpp	Removes special merge logic for GatherScatter+Broadcast and the GatherScatter branch in parallelize() for ParallelType::Group.
csrc/ops/indexing.cpp	gather() and scatter() output domains now use cloneWithoutRFactor() (Iteration type) instead of explicitly setting GatherScatter; no logic change beyond iter-type assignment.
csrc/ops/utils.cpp	Removes GatherScatter handling from promoteIterType and newOutputIterDomain; comment updated to match.
csrc/contiguity.cpp	Removes !GatherScatter guard in ContigIDs::build; also adopts std::ranges algorithms.
csrc/id_model/contiguity.cpp	Removes !GatherScatter guard in ContigIDGroups; also adopts std::ranges algorithms.
csrc/device_lower/validation.cpp	Narrows ParallelType::Group check to IterType::Iteration only; comment updated correctly.
csrc/fusion_segmenter.cpp	Removes the assertion that disjoint loop/logical is only allowed for scatter outputs with GatherScatter iter type, since that invariant no longer holds.
csrc/runtime/fusion_executor_cache.h	Adds cstdint include and fixes PrimDataType forward declaration to include std::uint8_t underlying type.
csrc/runtime/fusion_kernel_runtime.h	Same as fusion_executor_cache.h: adds cstdint and fixes PrimDataType forward declaration.
tests/cpp/test_scatter.cpp	Removes the GatherScatterIterType test that verified the (now-deleted) GatherScatter iter type was assigned to scatter output domains.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["gather() / scatter() call"] --> B["Build output IterDomains"]
    
    B --> C_old["OLD: if IterType::Iteration\n→ set IterType::GatherScatter\nelse keep original"]
    B --> C_new["NEW: cloneWithoutRFactor()\n(keeps original IterType)"]
    
    C_old --> D_old["Output domain has\nIterType::GatherScatter"]
    C_new --> D_new["Output domain has\nIterType::Iteration"]
    
    D_old --> E_old["Contiguity check:\nskip GatherScatter domains\n(never contig)"]
    D_new --> E_new["Contiguity check:\nnormal rules apply\n(can be contig)"]
    
    D_old --> F_old["fusion_segmenter:\ndisjoint loop/logical\nrequires GatherScatter"]
    D_new --> F_new["fusion_segmenter:\ndisjoint loop/logical\nallowed (no type check)"]
    
    D_old --> G_old["ParallelType::Group:\nallowed on Iteration or GatherScatter"]
    D_new --> G_new["ParallelType::Group:\nallowed on Iteration only"]

    style C_old fill:#ffcccc
    style D_old fill:#ffcccc
    style E_old fill:#ffcccc
    style F_old fill:#ffcccc
    style G_old fill:#ffcccc
    style C_new fill:#ccffcc
    style D_new fill:#ccffcc
    style E_new fill:#ccffcc
    style F_new fill:#ccffcc
    style G_new fill:#ccffcc

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_{Reviews (3): Last reviewed commit: "fix" | Re-trigger Greptile}

[naoyam]

!test --diff

[naoyam]

!test --diff

[jjsjann123]

blind stamp with full trust.