Repository: rust
Issue: AArch64 benchmarking assertion failure
Labels: O-Arm,T-libs-api,A-libtest,C-bug,O-AArch64

Repro:
```
#![cfg_attr(test, feature(test))]
#[cfg(test)] extern crate test;

#[cfg(test)]
mod tests {
    use test::{Bencher, black_box};

    #[bench]
    fn bench_map_scalar(b: &mut Bencher) {
        b.iter(|| {
            black_box(1)
        });
    }
}
```
.cargo/config
```
[target.aarch64-unknown-linux-gnu]
linker = "aarch64-linux-gnu-gcc"
ar = "aarch64-linux-gnu-ar"
runner = "qemu-aarch64 -L /usr/aarch64-linux-gnu"
```
Outputs:
```
$ RUST_BACKTRACE=1 cargo bench
   Compiling aarch64-libtest-busted v0.1.0 (file:///home/adam/aarch64-libtest-busted)
    Finished release [optimized] target(s) in 0.94 secs
     Running target/release/deps/aarch64_libtest_busted-1c6093a510eef424

running 1 test
test tests::bench_map_scalar ... bench:           0 ns/iter (+/- 0)

test result: ok. 0 passed; 0 failed; 0 ignored; 1 measured; 0 filtered out
```
```
$ RUST_BACKTRACE=1 cargo bench --target=aarch64-unknown-linux-gnu
    Finished release [optimized] target(s) in 0.0 secs
     Running target/aarch64-unknown-linux-gnu/release/deps/aarch64_libtest_busted-51d12e210b730146

running 1 test
test tests::bench_map_scalar ... thread 'main' panicked at 'assertion failed: pct <= hundred', /checkout/src/libtest/stats.rs:293:4
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at /checkout/src/libstd/sys_common/backtrace.rs:68
             at /checkout/src/libstd/sys_common/backtrace.rs:57
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:397
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:577
   5: std::panicking::begin_panic
             at /checkout/src/libstd/panicking.rs:538
   6: test::stats::percentile_of_sorted
             at /checkout/src/libtest/stats.rs:293
   7: test::stats::winsorize
             at /checkout/src/libtest/stats.rs:318
   8: aarch64_libtest_busted::tests::bench_map_scalar
   9: test::run_test
             at /checkout/src/libtest/lib.rs:1486
             at /checkout/src/libtest/lib.rs:1617
  10: test::run_tests_console
             at /checkout/src/libtest/lib.rs:1188
             at /checkout/src/libtest/lib.rs:975
  11: test::test_main
             at /checkout/src/libtest/lib.rs:291
  12: test::test_main_static
             at /checkout/src/libtest/lib.rs:327
  13: __rust_maybe_catch_panic
             at /checkout/src/libpanic_unwind/lib.rs:101
  14: std::rt::lang_start
             at /checkout/src/libstd/panicking.rs:459
             at /checkout/src/libstd/rt.rs:58
  15: main
  16: __libc_start_main
error: bench failed
```
```
$ rustc --version
rustc 1.24.0-nightly (dc39c3169 2017-12-17)
$ cargo --version
cargo 0.25.0-nightly (930f9d949 2017-12-05)
```
Offending assertion is [here](https://github.com/rust-lang/rust/blob/master/src/libtest/stats.rs#L293)