Re: Moving statements from one BB to other BB.

[Sandeep Maram]

Hi,

Consider the 2 for loops given below.

for (i = 0; i < N ; i++)
    {
      a[i]= 1;
    }

for (i = 0; i < N ; i++)
    {
      j = j+a[i];
    }

The headers of these 2 loops are bb_3, bb_6 respectively. They are as follows.

bb_3 (preds = {bb_4 bb_2 }, succs = {bb_4 bb_5 })
  {
  <bb 3>:
    # a_27 = PHI <a_18(4), a_17(D)(2)>
    # i_24 = PHI <i_7(4), 0(2)>
    # a_18 = VDEF <a_27> { a }
    a[i_24] = 1;
    i_7 = i_24 + 1;
    if (i_7 <= 999)
      goto <bb 4>;
    else
      goto <bb 5>;

  }

bb_6 (preds = {bb_5 bb_7 }, succs = {bb_7 bb_8 })
  {
  <bb 6>:
    # j_26 = PHI <0(5), j_12(7)>
    # i_25 = PHI <0(5), i_13(7)>
    # VUSE <a_18> { a }
    D.1189_10 = a[i_25];
    D.1190_11 = (unsigned int) D.1189_10;
    j_12 = D.1190_11 + j_26;
    i_13 = i_25 + 1;
    if (i_13 <= 999)
      goto <bb 7>;
    else
      goto <bb 8>;

  }

I am transfering statements from bb_6 to bb_3 using code -

for (bsi = bsi_start (loop_a->header); !bsi_end_p (bsi);)
    {
        if ((TREE_CODE (bsi_stmt (bsi)) != LABEL_EXPR) && (TREE_CODE
(bsi_stmt (bsi)) != COND_EXPR))
           {
            bsi_move_before (&bsi, &bsi_b_last);
           }
        else
           {
            bsi_next (&bsi);
           }
     }

After this the two BBs look like -

bb_6 (preds = {bb_5 bb_7 }, succs = {bb_7 bb_8 })
  {
  <bb 6>:
    # j_26 = PHI <0(5), j_12(7)>
    # i_25 = PHI <0(5), i_13(7)>
    if (i_13 <= 999)
      goto <bb 7>;
    else
      goto <bb 8>;

  }

bb_3 (preds = {bb_4 bb_2 }, succs = {bb_4 bb_5 })
  {
  <bb 3>:
    # a_27 = PHI <a_18(4), a_17(D)(2)>
    # i_24 = PHI <i_7(4), 0(2)>
    # a_18 = VDEF <a_27> { a }
    a[i_24] = 1;
    # VUSE <a_18> { a }
    D.1189_10 = a[i_25];
    D.1190_11 = (unsigned int) D.1189_10;
    j_12 = D.1190_11 + j_26;
    i_13 = i_25 + 1;
    i_7 = i_24 + 1;
    if (i_7 <= 999)
      goto <bb 4>;
    else
      goto <bb 5>;

  }

The iterator variables for the 2 loops are i_24, i_25 respectively. So
when the statements are transferred, there is a problem with i_25 in
bb_3 . How can I change the name of i_25 to i_24 ?

Thanks,
Sandeep.