Fix SLTIU instruction in MIPS assembler, disassembler, and simulator.

Fix SLTIU instruction in MIPS assembler, disassembler, and simulator.
Add regression assembler test.

R=zra@google.com

Committed: https://code.google.com/p/dart/source/detail?r=42362

[regis, 2014-12-13 01:28:26]

regis@google.com changed reviewers:
+ zra@google.com

[regis, 2014-12-13 01:28:26]

Good that we do not use this instruction too much so far :-)
My new code is using it a lot more and I was wondering why it was not working.

-- Regis

[regis, 2014-12-13 01:33:17]

Mmm, STLIU -> SLTIU

That was not the bug

[zra, 2014-12-13 03:12:59]

lgtm

https://codereview.chromium.org/802023002/diff/1/runtime/vm/assembler_mips.h
File runtime/vm/assembler_mips.h (right):

https://codereview.chromium.org/802023002/diff/1/runtime/vm/assembler_mips.h#...
runtime/vm/assembler_mips.h:714: void sltiu(Register rt, Register rs, const
Immediate& imm) {
This is a weird instruction.

[regis, 2014-12-15 16:45:15]

Not intuitive, for sure. But it allows to express values near the minimum and
near the maximum of the 32-bit unsigned range.

Thanks!

[regis, 2014-12-15 16:46:09]

Committed patchset #1 (id:1) manually as r42362.