[LLVMdev] not to break 'for' statement into basic blocks
Seung Jae Lee
lee225 at uiuc.edu
Sat Jul 14 16:48:02 CDT 2007
Dear LLVM guys,
Hi. I first became to be interested in the compiler work, especially LLVM, since last October, still I'm a novice on here. (My major is not CS, either. :-\)
Please forgive my ignorance.
LLVM optimization and other tools are really fantastic.
However I don't want LLVM breaks my 'for' statement in C code into basic blocks during compiling.
I'm sure this sounds really strange but there is a reason for me.
I almost made the backend for a target machine with LLVM.
But a peculiar thing is the assembly uses 'for' statement directly, not branching among basic blocks.
Furthermore, this assembly does not have the notion of 'br'instruction, phi-node and so on. Therefore, I have no choice without making 'for' in the assembly.
(Of course, equilvant 'br' instruction is used for 'if' statement. But it should be nested in 'demux' and 'mux' so I can't use this to represent 'for')
1) First, I tried to re-unite basic blocks which llvm-gcc spits out to make 'for' again.
But this is quite tricky. Generalizing it for the optimzed llvm bytecode is not easy.
2) So.. I wonder if it is possible to modify the llvm-gcc not to break 'for' but not sure about this.
I've heard 'clang' is newly released so I'm also wondering whether this can be modified for my goal.
3) A person recommended me to use GNU lightning, but still not sure about that.
4) A person also recommended me to make this assembly to "purely functional". This assembly, fortunately, supports 'call' instruction. So this can be a good choice for me, but unfortunately I don't have enough time to implementing it on the code after studying.
Could you, any body, tell me any advice, if you have?
My head is steaming.
Seung J. Lee
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