[llvm-bugs] [Bug 34078] New: Optimizer hangs with std::complex and -ffast-math

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=34078

            Bug ID: 34078
           Summary: Optimizer hangs with std::complex and -ffast-math
           Product: new-bugs
           Version: 4.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: lkoppel at uwaterloo.ca
                CC: llvm-bugs at lists.llvm.org

Created attachment 18911
  --> https://bugs.llvm.org/attachment.cgi?id=18911&action=edit
reduced .bc file from bugpoint

clang++ hangs indefinitely when compiling the following code with -O2
-ffast-math

#include <complex>
void f(double A) {
  double B = 1. - A - pow(A, 2) / 2.;
  std::complex<double> C = B + B;
  std::complex<double> D = 1. / C;
}

or the following code with -O1 -ffast-math

#include <complex>
void f(double A) {
  double B = 1. - A - pow(A, 2) / 2.;
  std::complex<double> C = B + B;
}

(I originally observed the bug while compiling
https://github.com/laurentkneip/opengv/blob/master/src/math/roots.cpp, and
reduced).

Bugpoint suggests it is the reassociate pass. Reduced output attached.

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