[PATCH, PR tree-optimization/68327] Compute vectype for live phi nodes when copmputing VF

[Richard Biener]

On Wed, Nov 18, 2015 at 2:53 PM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
> 2015-11-18 16:44 GMT+03:00 Richard Biener <richard.guenther@gmail.com>:
>> On Wed, Nov 18, 2015 at 12:34 PM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
>>> Hi,
>>>
>>> When we compute vectypes we skip non-relevant phi nodes.  But we process non-relevant alive statements and thus may need vectype of non-relevant live phi node to compute mask vectype.  This patch enables vectype computation for live phi nodes.  Botostrapped and regtested on x86_64-unknown-linux-gnu.  OK for trunk?
>>
>> Hmm.  What breaks if you instead skip all !relevant stmts and not
>> compute vectype for life but not relevant ones?  We won't ever
>> "vectorize" !relevant ones, that is, we don't need their vector type.
>
> I tried it and got regression in SLP.  It expected non-null vectype
> for non-releveant but live statement. Regression was in
> gcc/gcc/testsuite/gfortran.fortran-torture/execute/pr43390.f90

Because somebody put a vector type check before

  if (!STMT_VINFO_RELEVANT_P (stmt_info) && !bb_vinfo)
    return false;

@@ -7590,6 +7651,9 @@ vectorizable_comparison (gimple *stmt, g
   tree mask_type;
   tree mask;

+  if (!STMT_VINFO_RELEVANT_P (stmt_info) && !bb_vinfo)
+    return false;
+
   if (!VECTOR_BOOLEAN_TYPE_P (vectype))
     return false;

@@ -7602,8 +7666,6 @@ vectorizable_comparison (gimple *stmt, g
     ncopies = LOOP_VINFO_VECT_FACTOR (loop_vinfo) / nunits;

   gcc_assert (ncopies >= 1);
-  if (!STMT_VINFO_RELEVANT_P (stmt_info) && !bb_vinfo)
-    return false;

   if (STMT_VINFO_DEF_TYPE (stmt_info) != vect_internal_def
       && !(STMT_VINFO_DEF_TYPE (stmt_info) == vect_nested_cycle

fixes this particular fallout for me.

Richard.

> Ilya
>
>>
>> Richard.
>>
>>> Thanks,
>>> Ilya