Fix loop split incorrect count and probability

In tree-ssa-loop-split.c, split_loop and split_loop_on_cond does two
kind of split. split_loop only works for single loop and insert edge at
exit when split, while split_loop_on_cond is not limited to single loop
and insert edge at latch when split.  Both split behavior should consider
loop count and probability update.  For split_loop, loop split condition
is moved in front of loop1 and loop2; But split_loop_on_cond moves the
condition between loop1 and loop2, this patch does:
 1) profile count proportion for both original loop and copied loop
without dropping down the true branch's count;
 2) probability update in the two loops and between the two loops.

Regression tested pass.

Changes diff for split_loop and split_loop_on_cond cases:

1) diff base/loop-split.c.151t.lsplit patched/loop-split.c.152t.lsplit
...
   <bb 2> [local count: 118111600]:
   if (beg_5(D) < end_8(D))
     goto <bb 14>; [89.00%]
   else
     goto <bb 6>; [11.00%]

   <bb 14> [local count: 105119324]:
   if (beg2_6(D) < c_9(D))
-    goto <bb 15>; [100.00%]
+    goto <bb 15>; [33.00%]
   else
-    goto <bb 16>; [100.00%]
+    goto <bb 16>; [67.00%]

-  <bb 15> [local count: 105119324]:
+  <bb 15> [local count: 34689377]:
   _25 = beg_5(D) + 1;
   _26 = end_8(D) - beg_5(D);
   _27 = beg2_6(D) + _26;
   _28 = MIN_EXPR <c_9(D), _27>;

-  <bb 3> [local count: 955630225]:
+  <bb 3> [local count: 315357973]:
   # i_16 = PHI <i_11(8), beg_5(D)(15)>
   # j_17 = PHI <j_12(8), beg2_6(D)(15)>
   printf ("a: %d %d\n", i_16, j_17);
   i_11 = i_16 + 1;
   j_12 = j_17 + 1;
   if (j_12 < _28)
-    goto <bb 8>; [89.00%]
+    goto <bb 8>; [29.37%]
   else
-    goto <bb 17>; [11.00%]
+    goto <bb 17>; [70.63%]

-  <bb 8> [local count: 850510901]:
+  <bb 8> [local count: 280668596]:
   goto <bb 3>; [100.00%]

-  <bb 16> [local count: 105119324]:
+  <bb 16> [local count: 70429947]:
   # i_22 = PHI <beg_5(D)(14), i_29(17)>
   # j_23 = PHI <beg2_6(D)(14), j_30(17)>

   <bb 10> [local count: 955630225]:
   # i_2 = PHI <i_22(16), i_20(13)>
   # j_1 = PHI <j_23(16), j_21(13)>
   i_20 = i_2 + 1;
   j_21 = j_1 + 1;
   if (end_8(D) > i_20)
-    goto <bb 13>; [89.00%]
+    goto <bb 13>; [59.63%]
   else
-    goto <bb 9>; [11.00%]
+    goto <bb 9>; [40.37%]

-  <bb 13> [local count: 850510901]:
+  <bb 13> [local count: 569842305]:
   goto <bb 10>; [100.00%]

   <bb 17> [local count: 105119324]:
   # i_29 = PHI <i_11(3)>
   # j_30 = PHI <j_12(3)>
   if (end_8(D) > i_29)
     goto <bb 16>; [80.00%]
   else
     goto <bb 9>; [20.00%]

   <bb 9> [local count: 105119324]:

   <bb 6> [local count: 118111600]:
   return 0;

 }
   <bb 2> [local count: 118111600]:
-  if (beg_5(D) < end_8(D))
+  _1 = end_6(D) - beg_7(D);
+  j_9 = _1 + beg2_8(D);
+  if (end_6(D) > beg_7(D))
     goto <bb 14>; [89.00%]
   else
     goto <bb 6>; [11.00%]

   <bb 14> [local count: 105119324]:
-  if (beg2_6(D) < c_9(D))
-    goto <bb 15>; [100.00%]
+  if (j_9 >= c_11(D))
+    goto <bb 15>; [33.00%]
   else
-    goto <bb 16>; [100.00%]
+    goto <bb 16>; [67.00%]

-  <bb 15> [local count: 105119324]:
-  _25 = beg_5(D) + 1;
-  _26 = end_8(D) - beg_5(D);
-  _27 = beg2_6(D) + _26;
-  _28 = MIN_EXPR <c_9(D), _27>;
-
-  <bb 3> [local count: 955630225]:
-  # i_16 = PHI <i_11(8), beg_5(D)(15)>
-  # j_17 = PHI <j_12(8), beg2_6(D)(15)>
-  printf ("a: %d %d\n", i_16, j_17);
-  i_11 = i_16 + 1;
-  j_12 = j_17 + 1;
-  if (j_12 < _28)
-    goto <bb 8>; [89.00%]
+  <bb 15> [local count: 34689377]:
+  _27 = end_6(D) + -1;
+  _28 = beg_7(D) - end_6(D);
+  _29 = j_9 + _28;
+  _30 = _29 + 1;
+  _31 = MAX_EXPR <c_11(D), _30>;
+
+  <bb 3> [local count: 315357973]:
+  # i_18 = PHI <i_13(8), end_6(D)(15)>
+  # j_19 = PHI <j_14(8), j_9(15)>
+  printf ("a: %d %d\n", i_18, j_19);
+  i_13 = i_18 + -1;
+  j_14 = j_19 + -1;
+  if (j_14 >= _31)
+    goto <bb 8>; [29.37%]
   else
-    goto <bb 17>; [11.00%]
+    goto <bb 17>; [70.63%]

-  <bb 8> [local count: 850510901]:
+  <bb 8> [local count: 280668596]:
   goto <bb 3>; [100.00%]

-  <bb 16> [local count: 105119324]:
-  # i_22 = PHI <beg_5(D)(14), i_29(17)>
-  # j_23 = PHI <beg2_6(D)(14), j_30(17)>
+  <bb 16> [local count: 70429947]:
+  # i_24 = PHI <end_6(D)(14), i_32(17)>
+  # j_25 = PHI <j_9(14), j_33(17)>

   <bb 10> [local count: 955630225]:
-  # i_2 = PHI <i_22(16), i_20(13)>
-  # j_1 = PHI <j_23(16), j_21(13)>
-  i_20 = i_2 + 1;
-  j_21 = j_1 + 1;
-  if (end_8(D) > i_20)
+  # i_3 = PHI <i_24(16), i_22(13)>
+  # j_2 = PHI <j_25(16), j_23(13)>
+  i_22 = i_3 + -1;
+  j_23 = j_2 + -1;
+  if (beg_7(D) < i_22)
     goto <bb 13>; [89.00%]
   else
     goto <bb 9>; [11.00%]

-  <bb 13> [local count: 850510901]:
+  <bb 13> [local count: 569842305]:
   goto <bb 10>; [100.00%]

   <bb 17> [local count: 105119324]:
-  # i_29 = PHI <i_11(3)>
-  # j_30 = PHI <j_12(3)>
-  if (end_8(D) > i_29)
+  # i_32 = PHI <i_13(3)>
+  # j_33 = PHI <j_14(3)>
+  if (beg_7(D) < i_32)
     goto <bb 16>; [80.00%]
   else
     goto <bb 9>; [20.00%]

   <bb 9> [local count: 105119324]:

   <bb 6> [local count: 118111600]:
   return 0;

 }

2) diff base/loop-cond-split-1.c.151t.lsplit  patched/loop-cond-split-1.c.151t.lsplit:
...
   <bb 2> [local count: 118111600]:
   if (n_7(D) > 0)
     goto <bb 4>; [89.00%]
   else
     goto <bb 3>; [11.00%]

   <bb 3> [local count: 118111600]:
   return;

   <bb 4> [local count: 105119324]:
   pretmp_3 = ga;

-  <bb 5> [local count: 955630225]:
+  <bb 5> [local count: 315357973]:
   # i_13 = PHI <i_10(20), 0(4)>
   # prephitmp_12 = PHI <prephitmp_5(20), pretmp_3(4)>
   if (prephitmp_12 != 0)
     goto <bb 6>; [33.00%]
   else
     goto <bb 7>; [67.00%]

   <bb 6> [local count: 315357972]:
   _2 = do_something ();
   ga = _2;

-  <bb 7> [local count: 955630225]:
+  <bb 7> [local count: 315357973]:
   # prephitmp_5 = PHI <prephitmp_12(5), _2(6)>
   i_10 = inc (i_13);
   if (n_7(D) > i_10)
     goto <bb 21>; [89.00%]
   else
     goto <bb 11>; [11.00%]

   <bb 11> [local count: 105119324]:
   goto <bb 3>; [100.00%]

-  <bb 21> [local count: 850510901]:
+  <bb 21> [local count: 280668596]:
   if (prephitmp_12 != 0)
-    goto <bb 20>; [100.00%]
+    goto <bb 20>; [33.00%]
   else
-    goto <bb 19>; [INV]
+    goto <bb 19>; [67.00%]

-  <bb 20> [local count: 850510901]:
+  <bb 20> [local count: 280668596]:
   goto <bb 5>; [100.00%]

-  <bb 19> [count: 0]:
+  <bb 19> [local count: 70429947]:
   # i_23 = PHI <i_10(21)>
   # prephitmp_25 = PHI <prephitmp_5(21)>

-  <bb 12> [local count: 955630225]:
+  <bb 12> [local count: 640272252]:
   # i_15 = PHI <i_23(19), i_22(16)>
   # prephitmp_16 = PHI <prephitmp_25(19), prephitmp_16(16)>
   i_22 = inc (i_15);
   if (n_7(D) > i_22)
     goto <bb 16>; [89.00%]
   else
     goto <bb 11>; [11.00%]

-  <bb 16> [local count: 850510901]:
+  <bb 16> [local count: 569842305]:
   goto <bb 12>; [100.00%]

 }

gcc/ChangeLog:

2021-12-21  Xionghu Luo  <luoxhu@linux.ibm.com>

	* tree-ssa-loop-split.c (split_loop): Fix incorrect
	profile_count and probability.
	(do_split_loop_on_cond): Likewise.