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RVDS profiler for arm and exceptions, broken?

Note: This was originally posted on 24th March 2011 at http://forums.arm.com

Hello all,
I was advised by a co-worker to try arm's RVDS for profiling my code. I followed tutorial to load profiler sample project for xvid that comes with RVDS. Then, I created my own project that uses my code and I compile it and run to be able to see which functions needs optimization on ARM cpu.
However, I have impression that this entire thing is very buggy and doesn't work properly. The moment I try to enable optimiations (-O3 -Otime) it doesn't work at all. This code works properly on real device, so I know it works, but in RVDS emulator it does not work.
In short, when I compile with -O3 for example, then when I run profiler it works properly:
here's the output I get:
Attaching the profiler trace to component RTSM_EB_Cortex_A8.coretile.core.
Simulation is started
Loading symbols from amr-wb-fixed-test.axf...
Finished loading symbols.
Transferring target image
Enabled streaming trace.
ARM Profiler WARNING: Call chain max depth (511) exceeded. Call chain will be incorrect.
200 frames processed, time: 4.930
...

It runs fine, but at some point the green instruction graph drops and the exception graph goes up and the progress bar starts to increase fast with orange color.
and this is the pic when the instruction graph drops and the exception graph goes up [removed].

That same build runs without any issues with the debugger, but from profiler it has this problem.
Overall, it looks quite broken: I use limited amount of std libc: malloc, free, string.h functions and mem* functions. All of them resulted in exactly the same problem with exception coutner, so eventually I had to rewrite (provide my own implementations) of memcmp, memcpy etc, otherwise I wasn't able to use profiler at all! I have handcoded neon code and I wanted to profile the code to see what kind of improvement it gives me, but simply by including that asm file into the build makes the same problem with exception graph and it take TOO much time to run anything and profiler shows nonexistent functions at the end. The asm file uses gas for compilation, I changed it to arm's syntax, but it didn't help: the problem happens even if I do not call that asm optimized function, simply by including the object file into linker's list generated broken build.

Anybody can explain me what I do wrong, or the armcc is so broken and unusable. That's the impression I got.

PS> I downloaded latest compiler update, in release notes it mentions that there is a problem fixed that -O3 -Otime could result in invalid code... I was enthusiastic, thinking that I finally will be able to run my code, but it didn't help all. This code works on real devices, I build it with GCC and with MS's compiler for WinCE.
Here's the options that I pass to the compiler: CFG = --arm --cpu=6K -Otime -g, i tried also amt7-a, cortex-a8 etc, all have the same problem.

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Scott Douglass over 12 years ago

Note: This was originally posted on 25th March 2011 at http://forums.arm.com

This code works properly on real device, so I know it works, but in RVDS emulator it does not work.

It's quite possible for invalid code to work on one target or with one compiler or at one optimization level and not work on another target or another compiler or another optimization level. It's also quite possible that code is fine and you've encountered problems with the tools.

I think the "ARM Profiler WARNING" can be ignored for the time being; it's just telling you that the call chain information will be incomplete. I don't think it's having any effect on the execution You may be able to avoid the warning by disabliing data compression at link-time (I vaguely remember data decompression bogusly causing this warning).

That same build runs without any issues with the debugger, but from profiler it has this problem.

Do you mean that you can run (without profiling) the same image on the RTSM with no problem but when you try to profile it on the RTSM (without rebuilding) it has the exceptions problem?

Unfortunately I don't think it's possible to debug during the profile run to find out what is causing the exception. It might be worthwhile trying to include exception handlers that emit a message to find out which exception is happening and what the registers are (especially R14) when it happens.

I had to rewrite (provide my own implementations) of memcmp, memcpy etc, otherwise I wasn't able to use profiler at all

What happened when you used the versions of memcmp, etc. that are supplied with the tools?

This code works on real devices, I build it with GCC ...

Do you mean you can build it with gcc on run it sucessfully on a real ARM target?
Have you tried running and/or profiling the gcc-built version on the RTSM?
Are you using your version of memcmp, etc. with the gcc-built version?

I have handcoded neon code and I wanted to profile the code to see what kind of improvement it gives me,

The profiler may be able to help (after the exceptions problem is resolved) but the RTSM does not accurately model the timing of NEON instructions and memory access (and it is only approximate for others). It is accurate about the number of times a function/instruction was executed.

CFG = --arm --cpu=6K -Otime -g

I don't see the -O3 -- is it somewhere else?

Have you contacted ARM support (sw-support@arm.com) about this problem?
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Scott Douglass over 12 years ago

Note: This was originally posted on 25th March 2011 at http://forums.arm.com

This code works properly on real device, so I know it works, but in RVDS emulator it does not work.

It's quite possible for invalid code to work on one target or with one compiler or at one optimization level and not work on another target or another compiler or another optimization level. It's also quite possible that code is fine and you've encountered problems with the tools.

I think the "ARM Profiler WARNING" can be ignored for the time being; it's just telling you that the call chain information will be incomplete. I don't think it's having any effect on the execution You may be able to avoid the warning by disabliing data compression at link-time (I vaguely remember data decompression bogusly causing this warning).

That same build runs without any issues with the debugger, but from profiler it has this problem.

Do you mean that you can run (without profiling) the same image on the RTSM with no problem but when you try to profile it on the RTSM (without rebuilding) it has the exceptions problem?

Unfortunately I don't think it's possible to debug during the profile run to find out what is causing the exception. It might be worthwhile trying to include exception handlers that emit a message to find out which exception is happening and what the registers are (especially R14) when it happens.

I had to rewrite (provide my own implementations) of memcmp, memcpy etc, otherwise I wasn't able to use profiler at all

What happened when you used the versions of memcmp, etc. that are supplied with the tools?

This code works on real devices, I build it with GCC ...

Do you mean you can build it with gcc on run it sucessfully on a real ARM target?
Have you tried running and/or profiling the gcc-built version on the RTSM?
Are you using your version of memcmp, etc. with the gcc-built version?

I have handcoded neon code and I wanted to profile the code to see what kind of improvement it gives me,

The profiler may be able to help (after the exceptions problem is resolved) but the RTSM does not accurately model the timing of NEON instructions and memory access (and it is only approximate for others). It is accurate about the number of times a function/instruction was executed.

CFG = --arm --cpu=6K -Otime -g

I don't see the -O3 -- is it somewhere else?

Have you contacted ARM support (sw-support@arm.com) about this problem?
Cancel
Vote up 0 Vote down

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