Naturally, and sadly, turning off sanity checks in the runtime is
a noticable performance win. The particular test I'm running goes from
~1.5 s to ~1.3s.
Sanity checks are turned *on* when not optimizing, or when cfg
includes `rtdebug` or `rtassert`.
Monomorphize's normalization results in a 2% decrease in non-optimized
code size for libstd, so there's a negligible cost to removing it. This
also fixes several visit glue bugs because normalize wasn't considering
the differences in visit glue between types.
Closes#8720
This resolves issue #908.
Notable changes:
- On Windows, LLVM integrated assembler emits bad stack unwind tables when segmented stacks are enabled. However, unwind info directives in the assembly output are correct, so we generate assembly first and then run it through an external assembler, just like it is already done for Android builds.
- Linker is invoked via "g++" command instead of "gcc": g++ passes the appropriate magic parameters to the linker, which ensure correct registration of stack unwind tables in dynamic libraries.
- change all uses of Path in fn args to &P
- FileStream.read assumptions were wrong (libuv file io is non-positional)
- the above will mean that we "own" Seek impl info .. should probably
push it in UvFileDescriptor..
- needs more tests
Implement CharIterator as a separate struct, so that it can be .clone()'d. Fix `.char_range_at_reverse` so that it performs better, closer to the forwards version. This makes the reverse iterators and users like `.rfind()` perform better.
Before
test str::bench::char_iterator ... bench: 146 ns/iter (+/- 0)
test str::bench::char_iterator_ascii ... bench: 397 ns/iter (+/- 49)
test str::bench::char_iterator_rev ... bench: 576 ns/iter (+/- 8)
test str::bench::char_offset_iterator ... bench: 128 ns/iter (+/- 2)
test str::bench::char_offset_iterator_rev ... bench: 425 ns/iter (+/- 59)
After
test str::bench::char_iterator ... bench: 130 ns/iter (+/- 1)
test str::bench::char_iterator_ascii ... bench: 307 ns/iter (+/- 5)
test str::bench::char_iterator_rev ... bench: 185 ns/iter (+/- 8)
test str::bench::char_offset_iterator ... bench: 131 ns/iter (+/- 13)
test str::bench::char_offset_iterator_rev ... bench: 183 ns/iter (+/- 2)
To be able to use a string slice to represent the CharIterator, a function `slice_unchecked` is added, that does the same as `slice_bytes` but without any boundary checks.
It would be possible to implement CharIterator with pointer arithmetic to make it *much more efficient*, but since vec iterator is still improving, it's too early to attempt to re-implement it in other places. Hopefully CharIterator can be implemented on top of vec iterator without any unsafe code later.
Additional changes fix the documentation about null termination.
