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Bug 128

Summary: The nasm blitters should be rewritten in gcc syntax
Product: SDL Reporter: marchesin
Component: videoAssignee: marchesin
Status: RESOLVED WONTFIX QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: codepro
Version: HG 1.2   
Hardware: x86   
OS: All   

Description marchesin 2006-01-31 21:35:55 UTC 
The nasm blitters currently found under SDL12/src/hermes have numerous issues :
- the code is not PIC clean, which could result in crashes (and I think this one is the culprit for the crashes when using -O3)
- that code requires nasm (so it won't work on QNX or Mac OS X86)
- that code doesn't work on x86_64
- it adds a dependency on an external tool

The last 3 issues could be solved by doing a gcc rewrite, the first one could be done along the way by carefully saving/restoring ebx.
Comment 1 Alex Volkov 2006-03-15 18:17:15 UTC 
The first Hermes issue (PIC) has been resolved a little while back. Hermes nasm code now loads MMX constants via stack and so does not have any static memory variables anymore.
Comment 2 Kamil Kami&#324;ski 2006-05-26 12:55:20 UTC 
/usr/local/lib/gcc/x86_64-unknown-linux-gnu/4.1.0/../../../../x86_64-unknown-linux-gnu/bin/ld: build/.libs/SDL_blit_A.o: relocation R_X86_64_PC32 against `BlitRGBtoRGBPixelAlphaMMX3DNOW' can not be used when making a shared object; recompile with -fPIC
/usr/local/lib/gcc/x86_64-unknown-linux-gnu/4.1.0/../../../../x86_64-unknown-linux-gnu/bin/ld: final link failed: Bad value

Is there any chance to make this working? (compiled with -fPIC)
Comment 3 marchesin 2006-05-26 18:51:25 UTC 
I think that's a gcc bug. It can probably be worked around by changing :
inline static void BlitRGBtoRGBPixelAlphaMMX3DNOW(SDL_BlitInfo *info)
into 
static void BlitRGBtoRGBPixelAlphaMMX3DNOW(SDL_BlitInfo *info)

Oh btw, this has nothing to do with that bug.
Comment 4 Sam Lantinga 2006-09-23 19:15:33 UTC 
BlitRGBtoRGBPixelAlphaMMX3DNOW() is not inline anymore in subversion.
Comment 5 Ryan C. Gordon 2007-02-03 03:27:34 UTC 
Fwiw, the latest nasm builds can generate Intel Mach-O object files for Mac OS X.

I'd be inclined to say getting nasm to target QNX would be a better effort than converting all the Hermes code to GCC format.

If the PIC issues are resolved, I'd be inclined to flag this bug as WONTFIX.

--ryan.
Comment 6 Ryan C. Gordon 2007-02-15 05:55:05 UTC 
Hearing nothing, I'm closing this bug as WONTFIX. Having converted more than my share of assembly between GCC and nasm, I can imagine that we'll spend many years debugging it for little gain.

If an x86 platform can't use nasm, it will have to use the C fallbacks. That's how it goes. This would be a massive undertaking, and something that definitely should NOT happen in the 1.2 branch if nothing else.

--ryan.