diff options
| -rw-r--r-- | src/libextra/lib.rs | 2 | ||||
| -rw-r--r-- | src/libextra/test.rs | 16 |
2 files changed, 15 insertions, 3 deletions
diff --git a/src/libextra/lib.rs b/src/libextra/lib.rs index 519192fd177..109bf2e489b 100644 --- a/src/libextra/lib.rs +++ b/src/libextra/lib.rs @@ -29,7 +29,7 @@ Rust extras are part of the standard Rust distribution. html_favicon_url = "http://www.rust-lang.org/favicon.ico", html_root_url = "http://static.rust-lang.org/doc/master")]; -#[feature(macro_rules, globs, managed_boxes)]; +#[feature(macro_rules, globs, managed_boxes, asm)]; #[deny(non_camel_case_types)]; #[deny(missing_doc)]; diff --git a/src/libextra/test.rs b/src/libextra/test.rs index d1fffd9e515..d809d69b58e 100644 --- a/src/libextra/test.rs +++ b/src/libextra/test.rs @@ -1091,13 +1091,25 @@ impl MetricMap { // Benchmarking +/// A function that is opaque to the optimiser, to allow benchmarks to +/// pretend to use outputs to assist in avoiding dead-code +/// elimination. +/// +/// This function is a no-op, and does not even read from `dummy`. +pub fn black_box<T>(dummy: T) { + // we need to "use" the argument in some way LLVM can't + // introspect. + unsafe {asm!("" : : "r"(&dummy))} +} + + impl BenchHarness { /// Callback for benchmark functions to run in their body. - pub fn iter(&mut self, inner: ||) { + pub fn iter<T>(&mut self, inner: || -> T) { self.ns_start = precise_time_ns(); let k = self.iterations; for _ in range(0u64, k) { - inner(); + black_box(inner()); } self.ns_end = precise_time_ns(); } |