Comments on: Thumbs up http://hardwarebug.org/2009/03/25/thumbs-up/ Everything is broken Mon, 30 Aug 2010 09:33:38 +0000 hourly 1 http://wordpress.org/?v=3.0.1 By: mat http://hardwarebug.org/2009/03/25/thumbs-up/comment-page-1/#comment-29 mat Sun, 19 Apr 2009 08:40:24 +0000 http://hardwarebug.org/?p=125#comment-29 By any chance, have you some thumb number ? Now because of eabi force thumb interwork, I believe a clever complier could do interesting things : - use 32 bits for hot path code and 16 bits thumb for cold path code (error case, ...) By any chance, have you some thumb number ?

Now because of eabi force thumb interwork, I believe a clever complier could do interesting things :
- use 32 bits for hot path code and 16 bits thumb for cold path code (error case, …)

]]> By: Mans http://hardwarebug.org/2009/03/25/thumbs-up/comment-page-1/#comment-25 Mans Fri, 27 Mar 2009 09:22:40 +0000 http://hardwarebug.org/?p=125#comment-25 Switching to ARM state when entering the assembler functions works well. I did a quick benchmark comparing the overhead of calling a function with mode switching and without, and there wasn't much difference. Switching to ARM state when entering the assembler functions works well. I did a quick benchmark comparing the overhead of calling a function with mode switching and without, and there wasn’t much difference.

]]> By: Marcus Harnisch http://hardwarebug.org/2009/03/25/thumbs-up/comment-page-1/#comment-24 Marcus Harnisch Fri, 27 Mar 2009 08:19:57 +0000 http://hardwarebug.org/?p=125#comment-24 @Mans I don't expect the assembler code to be significantly smaller than before when compiled for Thumb-2. The benefit of simply recompiling it would be that you could actually take advantage of the speed optimizations. And Thumb-2 wouldn't be a special case any longer. -- Marcus @Mans
I don’t expect the assembler code to be significantly smaller than before when compiled for Thumb-2. The benefit of simply recompiling it would be that you could actually take advantage of the speed optimizations. And Thumb-2 wouldn’t be a special case any longer.

–
Marcus

]]> By: Laurent http://hardwarebug.org/2009/03/25/thumbs-up/comment-page-1/#comment-23 Laurent Thu, 26 Mar 2009 18:50:15 +0000 http://hardwarebug.org/?p=125#comment-23 Even if there will be mostly no size reduction by rewriting assembly routines to Thumb-2, there might be a gain from not requiring ISA switching (though I don't know how A8 behaves on that). Even if there will be mostly no size reduction by rewriting assembly routines to Thumb-2, there might be a gain from not requiring ISA switching (though I don’t know how A8 behaves on that).

]]> By: Mans http://hardwarebug.org/2009/03/25/thumbs-up/comment-page-1/#comment-22 Mans Wed, 25 Mar 2009 13:12:20 +0000 http://hardwarebug.org/?p=125#comment-22 The hand-written assembler would be almost entirely 32-bit instructions, so I doubt there would be any gains there. Also, the current GNU assembler doesn't fully support UAL. Including the assembler code as ARM in an otherwise Thumb-2 build works fine. I haven't investigated the MP3 performance yet. I have the RealView software but no JTAG hardware. I will try oprofile first. The hand-written assembler would be almost entirely 32-bit instructions, so I doubt there would be any gains there. Also, the current GNU assembler doesn’t fully support UAL. Including the assembler code as ARM in an otherwise Thumb-2 build works fine.

I haven’t investigated the MP3 performance yet. I have the RealView software but no JTAG hardware. I will try oprofile first.

]]> By: Marcus Harnisch http://hardwarebug.org/2009/03/25/thumbs-up/comment-page-1/#comment-21 Marcus Harnisch Wed, 25 Mar 2009 12:17:20 +0000 http://hardwarebug.org/?p=125#comment-21 Regarding omitting hand-written assembler: It would be interesting to see the effects of recompiling it for a Thumb-2 target. I suspect the modifications necessary are minor (if any). Thanks to UAL which most ARM tool chains support, the assembler source code differences between ARM and Thumb-2 are marginal in most cases. Regarding MP3 performance: Were you able to find out why MP3 is that much slower, unlike any of the other algorithms? Do you have access to RealView Profiler? Regards Marcus Regarding omitting hand-written assembler: It would be interesting to see the effects of recompiling it for a Thumb-2 target. I suspect the modifications necessary are minor (if any). Thanks to UAL which most ARM tool chains support, the assembler source code differences between ARM and Thumb-2 are marginal in most cases.

Regarding MP3 performance: Were you able to find out why MP3 is that much slower, unlike any of the other algorithms? Do you have access to RealView Profiler?

Regards
Marcus

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