[LLVMdev] Question about simple constant propagation pass

yunming zhang zhangyunming1990 at gmail.com
Wed Mar 27 19:15:48 PDT 2013


Hi,

I just started working with llvm, I am trying to test and improve the
constant propagation pass (-constprop),

I have two main questions,

1. I wrote my own test file, which has something like
   int a = 1
   int b = a + 2;
   int c = b + 3;
   print c

    However, non of the instruction was killed according to -stat. I think
it might due to the fact the llvm instructions generated was a bit
convoluted, but overall, I am not sure why this simple test case has no
instruction killed? Shouldn't c be just 6 and show at least two
instructions killed?

2. The description states that this pass is very simple. Can anyone point
me to a few directions that might be interesting to improve it? I am not
sure about why is it labeled "simple" ?

Thanks

Yunming
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