[llvm-bugs] [Bug 40453] New: The compiler-rt leads to loss of floating precision when GCC use compiler-rt instead of libgcc

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=40453

            Bug ID: 40453
           Summary: The compiler-rt leads to loss of floating precision
                    when GCC use compiler-rt instead of libgcc
           Product: compiler-rt
           Version: 7.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: compiler-rt
          Assignee: unassignedbugs at nondot.org
          Reporter: messagezsl at outlook.com
                CC: llvm-bugs at lists.llvm.org

Hi all

   Now we are try to use compiler-rt instead of libgcc when we use GCC to
compile program! but we find that comliper-rt will leads to loss of floating
precision, the following is detailed information:

  The program:

  int main()
  {
    double  one  = 1.0;
    double  tmp = 1.7976931348623157E308;
    double  ret =  one / tmp;

    printf(" ret : %E   \n", ret);

  }


  1、GCC compiler program and use libgcc:

  result:  

  ret : 5.562685E-309

  2、GCC compiler program and use compiler-rt:

  result:  

  ret : 0.000000E+00

  If anyone know the reason why compiler-rt will leads to loss of floating
precision
, Please reply soon when you are convenient! I will appreciate it!

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