The wrong optimization was: fold x < 0 into false, if x is known to be a result of an unsigned operation with overflow checks enabled.
It was done under the wrong assumption that the result of an overflow-checked unsigned operation fits into a signed integer and is positive.
This is wrong, because the result of an unsigned operation can be larger than Int.max and therefore, when used in a signed integer operation, be re-interpreted as a negative signed value.
Fixes a miscompile which resulted in a missing abort on arithmetic overflow.
rdar://73596890
Certain traps can't be supported on WASI, such as expectations for crashes, `setjmp` use, dynamic linking, multi-threading etc. These tests are marked as `UNSUPPORTED` when targeting Wasm/WASI.
Unchecked APIs must still perform checks in debug builds to ensure that invariants aren’t violated.
(I.e., these aren’t a license to perform invalid operations — they just let us get rid of the checks when we know for sure they are unnecessary.)
We can't actually check for NaN (because the notion doesn't exist for Comparable), but we can require that the endpoint is non-exceptional by checking if it equals itself.
* One-sided ranges and RangeExpression
* Remove redundant ClosedRange methods from String
* Fix up brittle tests
* Account for Substring update
* XFAIL range diagnostics on Linux
This decreases total testing time by over a minute on my old Mac Pro.
It probably has much less effect on systems with fewer cores, but shouldn't
be any worse there.
Swift SVN r22745
When the Index type of a Range is Comparable, we can reject invalid
ranges at their formation.
It might be worth injecting some checkability concept into ForwardIndex
so that even in generic contexts where Comparability is unknown, we can
do this same check in the Range constructor.
Also, remove pattern matching support for Ranges of RandomAccessIndex,
as that is covered by Interval.
Fixes <rdar://problem/16254937> (#Seed 4: Ranges with negative strides
are broken) to the extent possible (it's still possible to form an
invalid Range of indices that are not Comparable)
Fixes <rdar://problem/17164391> (Swift: Using ranges in for in for
counting down, causes the loop to go inifinely)
Fixes <rdar://problem/17580871> (Swift: Closed range with negative
endpoint excludes that endpoint)
Swift SVN r19903
