C front-end: evaluate __builtin_clz over constants #5735
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## develop #5735 +/- ##
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- Coverage 69.54% 32.22% -37.33%
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Files 1243 985 -258
Lines 100700 83689 -17011
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- Hits 70036 26970 -43066
- Misses 30664 56719 +26055
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tautschnig
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We seem to have a variety of ways to assert that something can be simplified, and perhaps we should consolidate. This test, I believe, introduces a new way. |
tautschnig
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You're of course right, this is a much better approach. Done. |
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| !int_constant.has_value() || *int_constant == 0 || | ||
| argument.type().id() != ID_unsignedbv) | ||
| { | ||
| return nil_exprt{}; |
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That just means it will be treated as a regular function call, not a "special function." So we fall back to using the library implementation.
| ^warning: ignoring | ||
| -- | ||
| For this example, __builtin_clz is fully evaluated in the front-end. This test | ||
| ensures that the function call no longer shows up. |
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Does it actually check that the function call is gone?
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Thank you for pointing out this outdated comment! This is now fixed.
This avoids warnings about missing declarations.
The Linux kernel uses __builtin_clz{,l,ll} in expressions that are expected
to be compile-time constants. To support this, evaluate such expressions
during type checking.
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The Linux kernel uses __builtin_clz(ll) in expressions that are expected
to be compile-time constants. To support this, evaluate such expressions
during type checking.