Turn off runtime assertions, turn on runtime optimizations

[brson]

The runtime has several performance-sensitive code paths that are compromising between going fast and making important assertions.

Right now the runtime knows about RUST_DEBUG and RUST_NDEBUG macros. When RUST_DEBUG is defined we do assertions about lock ownership and not much else. RUST_NDEBUG is defined by default, not RUST_DEBUG.

Let's make greater use of this by disabling expensive assertions and enabling optimizations. Because this involves disabling a lot of very checks we'll have RUST_DEBUG on by default.

Without RUST_DEBUG we can

• Run the box annihilator on normal task exit without worrying about obscuring cycle collector errors
• Turn off valgrind hints on stack allocation and switching paths that have real overhead
• Turn off check_stack_canary
• Turn off other expensive asserts

By default (with RUST_DEBUG) you get

• More locking assertions
• More calls to check_stack_canary
• More expensive asserts on the stack switching fast paths

Most likely this will involve changing the configure script too. Instead of --enable-debug we would have --disable-debug. Since this should end up with a noticeable performance difference between the two, configure and/or make all and make check might want to mention it, perhaps even in a handsome ascii-art box.

Notes

• Make sure to measure each to make sure it's worth doing
• Some of these performance issues are also addressed by Inline get_sp_limit, set_sp_limit, get_sp runtime functions #2521
• The box annihilator needs additional performance work

[huonw]

Triage 2013-08-05: I have a feeling that this is a WONTFIX, since the oldrt is disappearing (very?) soon. Is this correct @brson?

(Although this issue probably also applies to the newrt, e.g. for building with/without --cfg debug.)

[brson]

Obsolete.