[LLVMdev] A few inline assembly questions

Zack Rusin
Sun, 18 Mar 2007 16:04:14 -0000

Hey,

I'm contemplating adding llvm-gcc as a core platform to Qt, meaning we'd
release Qt unless we would make sure it compiles and works with llvm-gcc but
I have some problems with making it work cleanly so I just wanted to ask a
few simple questions.
The problems refer to llvm and llvm-gcc from respectively cvs/svn which, I'm
assuming, means upcoming 2.0 release.

1) we added a little inline assembly to do runtime detection of a few cpu
features. llvm-g++ crashes on the attached testcase (test.cpp).

2) i have code utilizing whatever vector insructions i can get my hands on to
speed up some very common rendering operations. llvm-gcc doesn't seem to
support mmx intrinsics which makes Qt compiled with llvm-gcc quite a bit
slower when it comes to graphics. test2.cpp shows in essence what we're
doing
in Qt. we basically have a very simple class that defines simple static
methods like negate/add/byte_mul/interpolate_pixel. now the question is if
there is any way of getting code like this to utilize vector instructions
with llvm-gcc. i wouldn't mind having llvm specific path there as long as it
works.

Zack
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