Refactored arraysetlengthT and arraysetlengthiT into a Single arraysetlengthT Template

[shivangshukla7020]

Changes Introduced

This PR merges arraysetlengthT and arraysetlengthiT into a single template, improving compile-time specialization and reducing redundancy. The key updates include:

• Unified arraysetlengthT and arraysetlengthiT into a single template, distinguishing them based on initialization behavior.
• Optimized memory handling for zero-initialized (arraysetlengthT) and non-zero-initialized (arraysetlengthiT) cases.
• Used emplace for non-trivial types instead of memcpy to ensure correct postblit behavior.
• Integrated gc_expandArrayUsed for in-place array expansion where applicable.
• Added D_ProfileGC support via _d_HookTraceImpl.

This refactoring improves performance by removing TypeInfo lookups and enabling better compile-time specialization.

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Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#21151"

[teodutu]

Overall this is looking good. I made some small suggestions.

[teodutu]

You can optimise this a little bit. Now a new template instance would be emitted for each array type like A[], const A[] etc, but you only need the unqualified type (UnqT). So draw inspiration from here [1] and unqualify the type in the compiler and pass isshared as an argument to reduce the number of generated type instances.

[1]

dmd/compiler/src/dmd/expressionsem.d

Lines 4852 to 4859 in 8bce4f5

	auto tiargs = new Objects();
	/*
	* Remove `inout`, `const`, `immutable` and `shared` to reduce the
	* number of generated `_d_newitemT` instances.
	*/
	auto t = ne.type.nextOf.unqualify(MODFlags.wild | MODFlags.const_ |
	MODFlags.immutable_ | MODFlags.shared_);
	tiargs.push(t);

[shivangshukla7020]

I’ll update it to follow that approach and avoid unnecessary template instantiations .

[teodutu]

You don't need this field. expressionsem.d creates a LoweredAssignExp which already contains the lowering. No need to duplicate it here.