[EgorBo] [X64] Fold BOX+ISINST to null if possible

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Build completed in 2 hours 1 minute.
dotnet/runtime#88989

CoreLib diffs

Found 2 files with textual diffs.

Summary of Code Size diffs:
(Lower is better)

Total bytes of base: 6549642
Total bytes of diff: 6549642
Total bytes of delta: 0 (0.00 % of base)


0 total files with Code Size differences (0 improved, 0 regressed), 1 unchanged.

0 total methods with Code Size differences (0 improved, 0 regressed), 52618 unchanged.

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Frameworks diffs

Diffs

Found 263 files with textual diffs.

Summary of Code Size diffs:
(Lower is better)

Total bytes of base: 38047486
Total bytes of diff: 38047486
Total bytes of delta: 0 (0.00 % of base)


0 total files with Code Size differences (0 improved, 0 regressed), 255 unchanged.

0 total methods with Code Size differences (0 improved, 0 regressed), 233033 unchanged.

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Artifacts:

• build-artifacts-main.zip (349 MB)
• build-clr-checked-main.zip (32 MB)
• build-artifacts-pr.zip (349 MB)
• build-clr-checked-pr.zip (32 MB)
• jit-diffs-corelib.zip (47 MB)
• diff-corelib.txt (433 B)
• jit-diffs-frameworks.zip (256 MB)
• diff-frameworks.txt (440 B)
• build-logs.txt (1 MB)

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