[Bug tree-optimization/64031] New: Vectorization of max/min is not robust enough

[Bug tree-optimization/64031] New: Vectorization of max/min is not robust enough

[jacques-henri.jourdan at inria dot Fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64031

            Bug ID: 64031
           Summary: Vectorization of max/min is not robust enough
           Product: gcc
           Version: 4.9.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jacques-henri.jourdan at inria dot Fr

The following code is sucessfully vectorized (using the minps instruction):

const int SIZE = 1<<15;

void test9(float * b)
{
  unsigned i;

  float *y =__builtin_assume_aligned(b, 16);

  for (i = 0; i < SIZE; i++)
  {
    float f = y[i];
    float f2 = f < f*f ? f : f*f;
    y[i] = f2;
  }
}

But not the following slightly modified version:

void test9(float * b)
{
  unsigned i;

  float *y =__builtin_assume_aligned(b, 16);

  for (i = 0; i < SIZE; i++)
  {
    float f = y[i];
    float f2 = f < f*f ? f : f*f;
    y[i] = f2*f2;
  }
}

Actually, it seems like vectorization of max/min operations fails as soon as
some computation is done with the result of this min/max operation.

[Bug tree-optimization/64031] Vectorization of max/min is not robust enough

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64031

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
-ffast-math lets it vectorize (using min directly). Otherwise, for the first
test, ifcvt gives (a<b)?a:b which is vectorized as such, but for the second
test, it doesn't unless we pass -fno-trapping-math. That seems a bit
inconsistent.

[Bug tree-optimization/64031] (un-)conditional execution state is not preserved by PRE/sink

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64031

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.0
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
This is now fixed in GCC 14.