Use a breakpoint instruction for a stop message on arm instead of

Use a breakpoint instruction for a stop message on arm instead of
a svc instruction (or hlt instruction on arm64).
The instructions svc and hlt are used in conjunction with a simulator only.
At least, gdb now stops on armv5te when hitting a stop message (no prompt).
Add support for printing stop message in disassembly on mips and arm64.
Clean up various bkpt codes on arm (now similar to arm64 and mips).

R=zra@google.com

Committed: https://code.google.com/p/dart/source/detail?r=45363

[regis, 2015-04-21 22:40:07]

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

[regis, 2015-04-21 22:40:08]

This solves the stop message issue on armv5te, but not perfectly (no prompt in
gdb, ctrl-c required). I am not sure what instruction will generate a proper
SIGTRAP and allow a continue.

At some time, I should verify the behavior in gdb on an Android device. But this
is not very important.

Thanks,
Regis

[zra, 2015-04-22 19:39:25]

lgtm with suggestion

https://codereview.chromium.org/1097413004/diff/1/runtime/vm/assembler_arm.cc
File runtime/vm/assembler_arm.cc (right):

https://codereview.chromium.org/1097413004/diff/1/runtime/vm/assembler_arm.cc...
runtime/vm/assembler_arm.cc:1473: void Assembler::svc(uint32_t imm24, Condition
cond) {
If this should only be used if we are using the simulator, you can and an ASSERT
for that here. Same for hlt on arm64.

[regis, 2015-04-22 20:28:35]

Thanks!

https://codereview.chromium.org/1097413004/diff/1/runtime/vm/assembler_arm.cc
File runtime/vm/assembler_arm.cc (right):

https://codereview.chromium.org/1097413004/diff/1/runtime/vm/assembler_arm.cc...
runtime/vm/assembler_arm.cc:1473: void Assembler::svc(uint32_t imm24, Condition
cond) {
On 2015/04/22 19:39:25, zra wrote:
> If this should only be used if we are using the simulator, you can and an
ASSERT
> for that here. Same for hlt on arm64.

Good idea. I actually removed the assembler methods svc() and hlt(), since they
are only used as constant instructions in the simulator and never emitted via
the assembler.

[regis, 2015-04-22 20:46:05]

Committed patchset #3 (id:40001) manually as r45363 (presubmit successful).