[Bug middle-end/81428] New: [7.1 regression] ICE: in build_one_cst, at tree.c:2079 with -O2. Fixed point division.

[jon at beniston dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81428

            Bug ID: 81428
           Summary: [7.1 regression] ICE: in build_one_cst, at tree.c:2079
                    with -O2. Fixed point division.
           Product: gcc
           Version: 7.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jon at beniston dot com
  Target Milestone: ---

Created attachment 41743
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41743&action=edit
Failing Testcase

The attached fixed point division test case fails for arm-eabi-gcc (and some
other targets, so not target specific) when compiled at -O2 with GCC 7.1.0. GCC
6.1.0 appears to be ok.

arm-eabi-gcc test.c -O2
test.c: In function ‘main’:
test.c:65:5: internal compiler error: in build_one_cst, at tree.c:2079
 int main()
     ^~~~

test.c:65:5: internal compiler error: Aborted
arm-eabi-gcc: internal compiler error: Aborted (program cc1)

Code is:

inline static v2si_t  vwfdivr (v2si_t x, v2si_t y) 
{
  v2si_t r;
  int i;
  for (i = 0; i < 2; i++)
    {
      long _Fract t1, t2, t3;
      t1 = lrbits(x[i]);
      t2 = lrbits(y[i]); 
      t3 = t1 / t2;
      r[i] = bitslr(t3);
    }  
  return r;
}

It appears to be related to the division, as changing that to another
arithmetic operator results in the ICE disappearing.