Skip unnecessary SLOAD for empty value-type array copy in IR

[tavian-dev]

Summary

Fixes #16307.

When copying a storage array of value types to another storage slot, the IR pipeline's copyValueArrayToStorageFunction unconditionally performs an sload on the source data area before entering the copy loop. For empty arrays (length 0), this SLOAD is wasted since the loop never executes.

This adds an early exit after resizeArray(dst, length) when length is zero, avoiding:

• The unnecessary sload on the source data area
• The keccak256 data slot computations for both source and destination
• The fullSlots division and loop overhead

Generated Yul before:

<resizeArray>(dst, length)

let srcPtr := <srcDataLocation>(src)     // keccak256
let dstSlot := <dstDataLocation>(dst)    // keccak256
let fullSlots := div(length, <itemsPerSlot>)
let srcSlotValue := sload(srcPtr)        // <-- unnecessary when length=0

Generated Yul after:

<resizeArray>(dst, length)

if iszero(length) { leave }              // skip everything for empty arrays

let srcPtr := <srcDataLocation>(src)
let dstSlot := <dstDataLocation>(dst)
let fullSlots := div(length, <itemsPerSlot>)
let srcSlotValue := sload(srcPtr)

Test plan

• Added semantic test array/copying/array_copy_empty_storage_push.sol exercising the exact pattern from the issue (array.push() = array.push())
• All 232 array semantic tests pass
• All 1637 semantic tests pass
• Full build + style check pass locally

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[nikola-matic]

Closing this as the issuein question has not been triaged, and is thus not ready for development.