Simplify all-zero or all-one constants in bitand/bitor

[tautschnig]

all-zeros in bitand yields zero, all-ones in bitor yield all-ones.

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[Copilot]

Pull request overview

Adds simplification rules for bitwise operations involving all-zero/all-one constants, plus new regression tests around expression simplification.

Changes:

• Simplify bitand to zero when any operand is an all-zero bitvector constant.
• Simplify bitor to all-ones when any operand is an all-ones constant.
• Add unit tests for bitand/all-zero and a few other simplify rules.

Reviewed changes

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

File	Description
src/util/simplify_expr_int.cpp	Implements early-return simplifications for bitand with all-zeros and bitor with all-ones.
unit/util/simplify_expr.cpp	Adds new simplification regression tests, including all-zero in bitand.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.47%. Comparing base (803f904) to head (64f338e).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8944   +/-   ##
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  Coverage    80.47%   80.47%           
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  Files         1704     1704           
  Lines       188694   188741   +47     
  Branches        73       73           
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+ Hits        151843   151887   +44     
- Misses       36851    36854    +3     

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[kroening]

We've got all_zeros_expr() and all_ones_expr(). In particular, from_integer will fail on bv_typet, which has no numerical interpretation.

[tautschnig]

We've got all_zeros_expr() and all_ones_expr(). In particular, from_integer will fail on bv_typet, which has no numerical interpretation.

Done and included an additional test for the possibly-failing case.