Fix overflow in number of bytes for long DMA BD lengths

[andrej]

closes #3033

[Copilot]

Pull request overview

Fixes an integer overflow when computing DMA buffer-descriptor lengths (elements → bytes / 32-bit words) so large transfers are validated and reported correctly, addressing #3033.

Changes:

• Widen BD length/offset calculations to 64-bit to prevent overflow during element-size multiplication.
• Update verifier alignment arithmetic to use 64-bit byte offsets.
• Add regression tests covering both “no false error” and “correct 64-bit diagnostic text” for very large lengths.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/bd-chains-and-dma-tasks/dma-tasks-to-npu/overflow-len-good.mlir	Adds a regression test for a large transfer that would overflow 32-bit when converted to bytes.
test/bd-chains-and-dma-tasks/dma-tasks-to-npu/overflow-len-bad.mlir	Adds a regression test ensuring diagnostics report the correct (non-truncated) byte counts.
lib/Targets/AIETargetXAIEV2.cpp	Widens internal tracking of BD length/offset for XAIEV2 codegen.
lib/Dialect/AIE/IR/AIEDialect.cpp	Uses a 64-bit accumulator for base+offset byte alignment checks in DMABDOp::verify().
include/aie/Dialect/AIE/IR/AIEOps.td	Changes DMABDOp::getLenInBytes() to 64-bit and makes offset-in-bytes 64-bit to avoid overflow.

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[andrej]

@copilot apply changes based on the comments in this thread

[hunhoffe]

Looks good! I had a few questions, but nothing blocking.