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J.F.
Joined: 22 Feb 2004
Posts: 2906
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 Posted: Sun Feb 27, 2005 1:20 pm Post subject: ABI Question |
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I was looking at something and ran into a question - what ABI does the EE gcc use? Be specific as there are a dozen MIPS ABIs floating around. I don't think I've seen this mentioned anywhere in the examples and what-not.
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mrbrown
Joined: 17 Jan 2004
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| Posted: Sun Feb 27, 2005 4:04 pm Post subject: |
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Cygnus' EABI.
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J.F.
Joined: 22 Feb 2004
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mrbrown
Joined: 17 Jan 2004
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| Posted: Mon Feb 28, 2005 6:40 am Post subject: |
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The EABI used in GCC for the EE uses 64-bit longs, and 32-bit pointers. Stack alignment is 16 bytes, not 8. IIRC, structs with 8 or fewer bytes are passed as values as opposed to 4 given in the spec. Perhaps pixel knows more about that, 'cause I also seem to remember that value being 16 at some point. It would make sense if it's 16 bytes because that's the most data a EE register can hold.
Everything else looks OK.
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J.F.
Joined: 22 Feb 2004
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| Posted: Mon Feb 28, 2005 12:00 pm Post subject: |
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| That's the kind of info some programmers need. We should probably make a doc for PS2Dev that details the EABI the toolchain gcc uses. We could start with something like the message I linked to above, then make the appropriate changes where needed. |
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mrbrown
Joined: 17 Jan 2004
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| Posted: Mon Feb 28, 2005 2:14 pm Post subject: |
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Thanks for volunteering!
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pixel
Joined: 30 Jan 2004
Posts: 791
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| Posted: Mon Feb 28, 2005 7:35 pm Post subject: |
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| mrbrown wrote: | The EABI used in GCC for the EE uses 64-bit longs, and 32-bit pointers. Stack alignment is 16 bytes, not 8. IIRC, structs with 8 or fewer bytes are passed as values as opposed to 4 given in the spec. Perhaps pixel knows more about that, 'cause I also seem to remember that value being 16 at some point. It would make sense if it's 16 bytes because that's the most data a EE register can hold.
Everything else looks OK. |
Never looked at how ee-gcc handles structs-passed-as-arguments. But it would sound strange since even though 16-bytes is the biggest thing EE can handle in its registers, gcc doesn't know about how to do anything with that apart of load and store. Trying...
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With a 16-bytes structure passed on first argument of a function, a0 contains a pointer to the structure.
With a 8-bytes structure passed on first argument of a function, the structure is contained straight inside the stack.
With a 4-bytes structure passed on first argument of a function, the structure is inside a0.
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pixel: A mischievous magical spirit associated with screen displays. The computer industry has frequently borrowed from mythology. Witness the sprites in computer graphics, the demons in artificial intelligence and the trolls in the marketing department. |
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mrbrown
Joined: 17 Jan 2004
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| Posted: Mon Feb 28, 2005 10:24 pm Post subject: |
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Ah - interesting that it would put it on the stack, but I guess according to the EABI it's a parameter.
It would be cool if 16 bytes were supported, and MMI instructions were used by the compiler to "depack" the register :).
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pixel
Joined: 30 Jan 2004
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| Posted: Mon Feb 28, 2005 10:36 pm Post subject: |
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| mrbrown wrote: | | It would be cool if 16 bytes were supported, and MMI instructions were used by the compiler to "depack" the register :). |
Thanks for volunteering ^_^
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pixel: A mischievous magical spirit associated with screen displays. The computer industry has frequently borrowed from mythology. Witness the sprites in computer graphics, the demons in artificial intelligence and the trolls in the marketing department. |
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J.F.
Joined: 22 Feb 2004
Posts: 2906
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| Posted: Tue Mar 01, 2005 10:55 am Post subject: |
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I'd be glad to put together the ABI spec file. Just keep the comments on various things coming and I'll make the changes in the base spec file. I might also post a question or two when I spot something that needs clarification.
:) |
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