[Bug middle-end/68232] gcc.dg/ifcvt-4.c fails on some arm configurations

[jgreenhalgh at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68232

James Greenhalgh <jgreenhalgh at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-11-06
                 CC|                            |jgreenhalgh at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from James Greenhalgh <jgreenhalgh at gcc dot gnu.org> ---
For this testcase to succeed you need a branch cost >= 1. I had thought that
this would cover all targets, but it looks like the ARM target defines branch
target to zero for some configurations.

  static int
  arm_default_branch_cost (bool speed_p, bool predictable_p ATTRIBUTE_UNUSED)
  {
    if (TARGET_32BIT)
      return (TARGET_THUMB2 && !speed_p) ? 1 : 4;
    else
      return (optimize > 0) ? 2 : 0;
  }

  static int
  arm_cortex_a5_branch_cost (bool speed_p, bool predictable_p)
  {
    return speed_p ? 0 : arm_default_branch_cost (speed_p, predictable_p);
  }

  /* Thumb-2 branches are relatively cheap on Cortex-M processors ("1 + P
cycles"
     on Cortex-M4, where P varies from 1 to 3 according to some criteria),
since
     sequences of non-executed instructions in IT blocks probably take the same
     amount of time as executed instructions (and the IT instruction itself
takes
     space in icache).  This function was experimentally determined to give
good
     results on a popular embedded benchmark.  */

  static int
  arm_cortex_m_branch_cost (bool speed_p, bool predictable_p)
  {
    return (TARGET_32BIT && speed_p) ? 1
           : arm_default_branch_cost (speed_p, predictable_p);
  }

This test should be an XFAIL wherever BRANCH_COST == 0, but I'm not sure what
the polite way to explain that to the test harness is.

Confirmed (and expected) anyway.