[lno] [RFC] if-conversion and auto vectorizer

[Devang Patel]

OK. So far I have coded transformation to transform

bar ()
{
   int A[N+1], B[N+1], C[N+1], D[N+1];
   int i;

   for (i = 1; i<N; i++)
     {
       if (A[i] > 0)
         {
           A[i] = A[i] + C[i];
           B[i] = A[i] + 1;
         }
       else
         {
           A[i] = D[i];
           B[i] = D[i] + 1;
         }
     }
   ibar(A);
   ibar(B);
}

into :

bar ()
{
   int i;
   int D[17];
   int C[17];
   int B[17];
   int A[17];
   int T.5;
   int T.4;
   int T.3;
   int T.2;
   int T.1;
   int T.0;

   # BLOCK 0
   # PRED: ENTRY [100.0%]  (fallthru,exec)
   # SUCC: 1 [100.0%]  (fallthru,exec)

   # BLOCK 1
   # PRED: 6 [100.0%]  (fallthru) 0 [100.0%]  (fallthru,exec)
   # i_1 = PHI <1(0), i_15(6)>;
<L0>:;
   T.0_3 = if (1)
     {
       A[i_1];
     };
   if (T.0_3 > 0) goto <L1>; else goto <L2>;
   # SUCC: 3 [21.0%]  (false,exec) 2 [79.0%]  (true,exec)

   # BLOCK 2
   # PRED: 1 [79.0%]  (true,exec)
<L1>:;
   T.1_9 = if (1 && T.0_3 > 0)
     {
       C[i_1];
     };
   T.2_10 = if (1 && T.0_3 > 0)
     {
       T.0_3 + T.1_9;
     };
   A[i_1] = if (1 && T.0_3 > 0)
     {
       T.2_10
     };
   T.3_12 = if (1 && T.0_3 > 0)
     {
       T.2_10 + 1;
     };
   B[i_1] = if (1 && T.0_3 > 0)
     {
       T.3_12
     };
   goto <bb 4> (<L3>);
   # SUCC: 4 [100.0%]  (fallthru,exec)

   # BLOCK 3
   # PRED: 1 [21.0%]  (false,exec)
<L2>:;
   T.4_5 = if (1 && !(T.0_3 > 0))
     {
       D[i_1];
     };
   A[i_1] = if (1 && !(T.0_3 > 0))
     {
       T.4_5
     };
   T.5_7 = if (1 && !(T.0_3 > 0))
     {
       T.4_5 + 1;
     };
   B[i_1] = if (1 && !(T.0_3 > 0))
     {
       T.5_7
     };
   # SUCC: 4 [100.0%]  (fallthru,exec)

   # BLOCK 4
   # PRED: 3 [100.0%]  (fallthru,exec) 2 [100.0%]  (fallthru,exec)
<L3>:;
   i_15 = i_1 + 1;
   if (i_15 <= 15) goto <L8>; else goto <L5>;
   # SUCC: 5 [11.0%]  (false,exec) 6 [89.0%]  (true,exec)

   # BLOCK 6
   # PRED: 4 [89.0%]  (true,exec)
<L8>:;
   goto <bb 1> (<L0>);
   # SUCC: 1 [100.0%]  (fallthru)

   # BLOCK 5
   # PRED: 4 [11.0%]  (false,exec)
<L5>:;
   ibar (&A);
   ibar (&B);
   return;
   # SUCC: EXIT [100.0%]

}

I spent lot of time unnecessary to create super block inside loop by
merging block 2 and 3 into block 1.

If vectorizer can not vectorize this loop then it will be reverted to
original form using loop versioning. Am I on the right track ?

Thanks,
--
Devang

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