[mlir][Sol] Support packed and unpacked string storage layouts

[PavelKopyl]

This also adds support for:

• Short strings (length < 32 bytes, packed encoding)
• Long strings (length >= 32 bytes, unpacked encoding)
• String operations: push(), push(x), pop(), length, indexing
• Conversions between memory and storage representations

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[Copilot]

Pull request overview

This PR extends the Sol dialect lowering to support Solidity bytes/string storage layouts (short in-slot encoding vs long out-of-place encoding) and introduces dedicated string push operations to model push, push(x), pop, length, indexing, and storage↔memory conversions in the Sol→Yul pipeline.

Changes:

• Add sol.push_string and sol.push_string_void ops and lower them to new EVM/Yul builder helpers.
• Implement storage-specific string helpers in evm::Builder (length decode, push/pop, indexing, copy to/from memory/storage).
• Extend GEP handling to account for storage reference types (string/struct) and wire new ops into the conversion pass.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
mlir/lib/Dialect/Sol/SolOps.cpp	Adds PushStringVoidOp builder; expands storage ref-type handling in GepOp::build.
mlir/lib/Conversion/SolToStandard/SolToYul.cpp	Adds lowering patterns for the new string push ops; updates pop/GEP/copy paths for strings.
mlir/lib/Conversion/SolToStandard/SolToStandardPass.cpp	Marks new string push ops illegal so they are lowered in stage1.
mlir/lib/Conversion/SolToStandard/EVMUtil.cpp	Adds substantial string storage/memory logic (length decode, push/pop, indexing, copy).
mlir/include/mlir/Dialect/Sol/SolOps.td	Declares sol.push_string / sol.push_string_void.
mlir/include/mlir/Conversion/SolToStandard/Util.h	Adds BuilderExt::genCeilDivision helper.
mlir/include/mlir/Conversion/SolToStandard/EVMUtil.h	Exposes new evm::Builder APIs for string operations and generic copy.

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[abinavpp]

Thanks a lot! The impl looks nice! Wish we could figure out a way to remove the ad-hoc push ops somehow.

[PavelKopyl]

Thanks a lot! The impl looks nice! Wish we could figure out a way to remove the ad-hoc push ops somehow.

Thank you!. I've removed PushStringVoidOp and extended PushOp.