bugpoint should run tests in parallel

[llvmbot]

Bugzilla Link	539
Version	trunk
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@Bigcheese

Extended Description

I will send a box of salty dead fish to anyone who can multithread bugpoint (or
rather, get bugpoint to spawn parallel gcc/llc processes in some effective manner)

[lattner]

That would be cool, but I wouldn't hold your breath over it. Bugpoint gets
hacked on when people get annoyed at it enough to do something. :)

[llvmbot]

Mine.

[llvmbot]

Reid, cool! A few thoughts/requests:

1. Instead of just forking at each branch in the (binary) tree of tests bugpoint
   does (when trying to nail a function being miscompiled), can you turn it into an
   n-ary tree? i.e. at the first stage, compile say 4 threads x (1/4 the program
   with llc, 3/4 with native) - this will increase the amount of "wasted"
   computation but should greatly speed up bugpointing real-world programs on
   people's shiny new multicore systems...

2. when bugpoint is down to testing single instructions, can you make a "work
   list" out of these and have however many threads the user says are available
   chipping away at it?

3. (for extra fish) - get 1) and 2) working when trying to find JIT bugs!

4. email me your address (I'm not joking about the fish ;)

[llvmbot]

Turning loop extraction into a work-list kinda thing would be cool, too.

(sorry for being greedy :( )

[arsenm]

Obsoleted by llvm-reduce which does support parallel reduction