[cfe-dev] Question on LiveVariables analysis

[Guoping Long]

Hi,

   While LiveVariables analysis (tools/clang/lib/Analysis/LiveVariables.cpp)
does not generate any output? Specifically, for this simple program:
  1 int main(int argc, char *argv[])
  2 {
  3   int a,b,c,d,x;
  4
  5   a = 3;   //Basic block B1
  6   b = 5;
  7   d = 4;
  8   x = 100;
  9
 10   if(a>b){  //Basic block B2
 11     c = a+b;
 12     d = 2;
 13   }
 14
 15   c = 4;   //Basic block B3
 16   return b * d + c;
 17 }
This simple example is taken from this wiki page illustrating live variables
analysis (http://en.wikipedia.org/wiki/Live_variable_analysis).
Both B2 and B3 should have live variables, but the output (using
LiveVariables::dumpBlockLiveness(SourceManager &)) says no live variables
exist. I am trying to use this analysis as an example on how to write a good
analysis algorithm for Clang, but really did not expect this behavior for
this analysis.
Anybody who knows the answer please let me know. Many thanks!!!

--------
Guoping
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