[LLVMdev] Porting LLVM backend is no fun yet

Greg McGary greg at mcgary.org
Mon Apr 13 13:15:39 PDT 2009

Evan Cheng wrote:
> Surely these are two separate issues. TableGen being less than capable 
> then CGEN doesn't have anything to do with the overall quality of rest 
> of LLVM. Yes it's true it could be harder to port LLVM to certain 
> architectures. But it's probably not the case for every target. Can 
> you do a good port of x86 using CGEN? :-)

Hi Evan,

Forgive me for focusing so much on complaints and omitting praise.  I 
enthusiastically applaud LLVM in every other respect!  LLVM is the 
coolest, grooviest swiss-army-knife of compiler technology I have had 
the pleasure of working with.  I'm certain that my own deficient C++ 
skills contributes to my frustrations, and is hardly the fault of LLVM.  
The thrust of my message is that I want to learn better what TableGen 
can already do, and contribute to making it a more flexible and complete 
target description tool.  One reason I had an easier time with the 
CGEN+GCC port was because there were already several good quality ports 
to targets that were very similar (m32r was one).  LLVM just isn't as 
old and broadly ported as CGEN+GCC, so I'm not benefiting as much from 
others' work.  Now I get to be something of a pioneer and will 
doubtlessly acquire some arrows in my back to prove it. 8^)


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