[llvm-dev] Dataflow analysis regression in 3.7

Johan Engelen via llvm-dev llvm-dev at lists.llvm.org
Wed Jul 5 15:59:45 PDT 2017

Hi all,
  I just found an optimization regression regarding simple
dataflow/constprop analysis:

This code
int dataflow(int b) {
  int a;

  if (b==4)
    a = 3*b; // fully optimized when changed to a = 3;
    a = 5;

  if (a == 4)
    return 0;
    return 1;
is no longer optimized to just a "return 1". The regression happened in
LLVM 3.6 --> 3.7.

Is this a known regression? I couldn't find it in the bug tracker (but
don't really know which keywords to look for...)

Kind regards,
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