[Qemu-devel] [Bug 1233225] Re: mips/mipsel linux user float division problem

[Stefan Weil]

Here is the related commit found by git bisect:

$ git bisect bad
68473f15d4c9948986618f63828825beafcaf1cf is the first bad commit
commit 68473f15d4c9948986618f63828825beafcaf1cf
Author: Richard Henderson <address@hidden>
Date:   Sun Feb 10 10:30:46 2013 -0800

    mips64-linux-user: Enable 64-bit address mode and fpu
    
    Signed-off-by: Richard Henderson <address@hidden>
    Signed-off-by: Aurelien Jarno <address@hidden>

:040000 040000 de3caa25e43aaeb7d992715b2efc6804a7d0d633
b007b2a9809547197952ca4d36fbd29f89aab470 M      target-mips

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https://bugs.launchpad.net/bugs/1233225

Title:
  mips/mipsel linux user float division problem

Status in QEMU:
  Confirmed

Bug description:
  Hi,

  I tested the following with the qemu git HEAD as of 2013-09-30 on
  Debian stable and testing. My host runs amd64 but I also tried this
  out inside a i386 chroot with the same result. The problem occurs for
  mips and mipsel. Given the following program:

  #include <stdio.h>
  int main(int argc, char **argv)
  {
      int a = 1;
      double d = a/2.0;
      printf("%f\n", d);
      return 0;
  }

  Instead of printing 0.5, it will print 2.0 if executed in qemu user
  mode.

  $ mipsel-linux-gnu-gcc mipstest.c
  $ ~/qemu/mipsel-linux-user/qemu-mipsel ./a.out
  2.0

  Expecting this to be a problem with my cross compiler (gcc-4.4 from
  emdebian) I ran a fully emulated debian squeeze environment inside
  qemu. There, I compiled the same program natively with gcc and as
  expected got 0.5 as the output. I also copied the cross compiled
  binary inside the emulated environment and also got 0.5 when I ran it.
  So the same mips/mipsel binary produces different output depending on
  whether it is run in a fully emulated environment or qemu user mode.

  Can anybody else reproduce this problem?

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