[PATCH] new tree-ssa pass (documented too)

[Andrew Pinski]

I think I did not explain my self fully maybe but Steven asked
me to explain this more fully.

Two return statements are merged into one by creating a new basic
block and changing those two basic blocks containing the return
statements to go directly to the new basic block.

So
if (a)
   return b;
else
   return c;

is transformed into:

if (a)
   {
     Temp1 = b;
     goto newbasicblock;
   }
else
   {
     Temp1 = b;
     goto newbasicblock;
   }
newbasicblock:
   return Temp1;



Oh, and I had forgot a testcase also, I will send a patch to fix the 
xfails later in this test:
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-return1 -fdump-tree-tailc-details 
-fdump-tree-phiopt1-details" } */
/* PR optimization/14135 */

int f(int i)
{
   int result;
   result = t(i);
   if (result)
     return result;
   return 0;
}

/* We should merge the return in two basic blocks into one return 
statement.  */
/* { dg-final { scan-tree-dump-times "return" 1 "return1" } } */
/* We should convert one COND_EXPRs into straightline code.  */
/* { dg-final { scan-tree-dump-times "straightline" 1 "phiopt1" {xfail 
*-*-* } } */
/* Also we should have found that the call to t is tail called.   */
/* { dg-final { scan-tree-dump-times "Found tail call" 1 "tailc" {xfail 
*-*-*} } } */