Track local frames incrementally during execution
https://github.com/rust-lang/miri/pull/2646 currently introduces a performance regression. This change removes that regression, and provides a minor perf improvement.
The existing lazy strategy for tracking the span we want to display is as efficient as it is only because we often create a `CurrentSpan` then never call `.get()`. Most of the calls to the `before_memory_read` and `before_memory_write` hooks do not create any event that we store in `AllocHistory`. But data races are totally different, any memory read or write may race, so every call to those hooks needs to access to the current local span.
So this changes to a strategy where we update some state in a `Thread` and `FrameExtra` incrementally, upon entering and existing each function call.
Before:
```
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/backtraces/Cargo.toml
Time (mean ± σ): 5.532 s ± 0.022 s [User: 5.444 s, System: 0.073 s]
Range (min … max): 5.516 s … 5.569 s 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/mse/Cargo.toml
Time (mean ± σ): 831.4 ms ± 3.0 ms [User: 783.8 ms, System: 46.7 ms]
Range (min … max): 828.7 ms … 836.1 ms 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/serde1/Cargo.toml
Time (mean ± σ): 1.975 s ± 0.021 s [User: 1.914 s, System: 0.059 s]
Range (min … max): 1.939 s … 1.990 s 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/serde2/Cargo.toml
Time (mean ± σ): 4.060 s ± 0.051 s [User: 3.983 s, System: 0.071 s]
Range (min … max): 3.972 s … 4.100 s 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/slice-get-unchecked/Cargo.toml
Time (mean ± σ): 784.9 ms ± 8.2 ms [User: 746.5 ms, System: 37.7 ms]
Range (min … max): 772.9 ms … 793.3 ms 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/unicode/Cargo.toml
Time (mean ± σ): 1.679 s ± 0.006 s [User: 1.623 s, System: 0.055 s]
Range (min … max): 1.673 s … 1.687 s 5 runs
```
After:
```
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/backtraces/Cargo.toml
Time (mean ± σ): 5.330 s ± 0.037 s [User: 5.232 s, System: 0.084 s]
Range (min … max): 5.280 s … 5.383 s 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/mse/Cargo.toml
Time (mean ± σ): 818.9 ms ± 3.7 ms [User: 776.8 ms, System: 41.3 ms]
Range (min … max): 813.5 ms … 822.5 ms 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/serde1/Cargo.toml
Time (mean ± σ): 1.927 s ± 0.011 s [User: 1.864 s, System: 0.061 s]
Range (min … max): 1.917 s … 1.945 s 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/serde2/Cargo.toml
Time (mean ± σ): 3.974 s ± 0.020 s [User: 3.893 s, System: 0.076 s]
Range (min … max): 3.956 s … 4.004 s 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/slice-get-unchecked/Cargo.toml
Time (mean ± σ): 780.0 ms ± 5.3 ms [User: 740.3 ms, System: 39.0 ms]
Range (min … max): 771.2 ms … 784.5 ms 5 runs
Benchmark 1: cargo +miri miri run --manifest-path /home/ben/miri/bench-cargo-miri/unicode/Cargo.toml
Time (mean ± σ): 1.643 s ± 0.007 s [User: 1.584 s, System: 0.058 s]
Range (min … max): 1.635 s … 1.654 s 5 runs
```
(This change is marginal, but the point is that it avoids a much more significant regression)
make miri-seed a regular integer, and also set layout-seed in many-seeds
This makes the seed format consistent between `-Zlayout-seed` and `-Zmiri-seed`.
try_normalize_after_erasing_regions: promote an assertion to always run
In https://github.com/rust-lang/miri/issues/2433 this assertion has been seen to trigger, so it might be worth actually checking this? Regressing debug assertions are very easy to miss until much later, and then they become quite hard to debug.
Don't duplicate last cdb debuginfo test command
cdb scripts interpret a blank line to mean "repeat the last command", similar to what happens when running the debugger from a console. The code for compiletest that constructs the debugger script was inserting a blank line between the last command and the "quit" command. This caused the last command to be executed twice. This can cause some confusion since the `-check` lines are expecting the output in a certain order. But printing the last command twice causes that order-assumption to fail, and that can cause confusion.
This fixes it by removing the blank line.
AFAICT, gdb and lldb scripts don't have the same behavior with blank lines (and the gdb code doesn't add any blank lines anyways).
* Fix doc examples for Platforms with underaligned integer primitives.
* Mutable pointer doc examples use mutable pointers.
* Fill out tracking issue.
* Minor formatting changes.
