[PATCH] Fix up slpeel_tree_peel_loop_to_edge (PR tree-optimization/52255)

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

On this testcase we ICE, because slpeel_tree_peel_loop_to_edge is first
called with a loop that has a virtual PHI and no virtual PHI in the loop
exit bb and this function doesn't update the vop properly after inserting
second loop and adding all the conditional guards, then vect_loop_versioning
calls loop_version which deep inside of it performs
verify_loop_closed_ssa (true)
which ICEs on the invalid SSA.  If that check is commented out, we proceed
with optionally doing another slpeel_tree_peel_loop_to_edge and finally
when all loops are vectorized, mark the vop for renaming and update ssa,
which fixes it up.

Here is an attempt to ensure the vop is updated properly, because calling
update_ssa in each slpeel_tree_peel_loop_to_edge would be IMHO too
expensive.  The slpeel_tree_peel_loop_to_edge and its helpers already
DTRT for all other PHIs, the problem with virtual PHIs is that the loop
closed SSA form for other PHIs requires a dummy PHI on the exit bb if
it is used after the loop, but for virtual PHIs it doesn't have this
requirement.  The simplest patch below just adds an extra PHI even
for the vop if there isn't any and the loop has it, then the routines in
multiple places just DTRT.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2012-02-16  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/52255
	* tree-vect-loop-manip.c (slpeel_tree_peel_loop_to_edge): If
	loop->header has virtual PHI, but exit_e->dest doesn't, add
	virtual PHI to exit_e->dest and adjust all uses after the loop.

	* gcc.c-torture/compile/pr52255.c: New test.

--- gcc/tree-vect-loop-manip.c.jj	2012-01-03 16:22:48.000000000 +0100
+++ gcc/tree-vect-loop-manip.c	2012-02-15 20:15:27.816120830 +0100
@@ -1171,6 +1171,7 @@ slpeel_tree_peel_loop_to_edge (struct lo
   basic_block bb_before_first_loop;
   basic_block bb_between_loops;
   basic_block new_exit_bb;
+  gimple_stmt_iterator gsi;
   edge exit_e = single_exit (loop);
   LOC loop_loc;
   tree cost_pre_condition = NULL_TREE;
@@ -1184,6 +1185,43 @@ slpeel_tree_peel_loop_to_edge (struct lo
    the function tree_duplicate_bb is called.  */
   gimple_register_cfg_hooks ();
 
+  /* If the loop has a virtual PHI, but exit bb doesn't, create a virtual PHI
+     in the exit bb and rename all the uses after the loop.  This simplifies
+     the *guard[12] routines, which assume loop closed SSA form for all PHIs
+     (but normally loop closed SSA form doesn't require virtual PHIs to be
+     in the same form).  Doing this early simplifies the checking what
+     uses should be renamed.  */
+  for (gsi = gsi_start_phis (loop->header); !gsi_end_p (gsi); gsi_next (&gsi))
+    if (!is_gimple_reg (gimple_phi_result (gsi_stmt (gsi))))
+      {
+	gimple phi = gsi_stmt (gsi);
+	for (gsi = gsi_start_phis (exit_e->dest);
+	     !gsi_end_p (gsi); gsi_next (&gsi))
+	  if (!is_gimple_reg (gimple_phi_result (gsi_stmt (gsi))))
+	    break;
+	if (gsi_end_p (gsi))
+	  {
+	    gimple new_phi = create_phi_node (SSA_NAME_VAR (PHI_RESULT (phi)),
+					      exit_e->dest);
+	    tree vop = PHI_ARG_DEF_FROM_EDGE (phi, EDGE_SUCC (loop->latch, 0));
+	    source_location loc
+	      = gimple_phi_arg_location_from_edge (phi, EDGE_SUCC (loop->latch,
+								   0));
+	    imm_use_iterator imm_iter;
+	    gimple stmt;
+	    tree new_vop = make_ssa_name (SSA_NAME_VAR (PHI_RESULT (phi)),
+					  new_phi);
+	    use_operand_p use_p;
+
+	    add_phi_arg (new_phi, vop, exit_e, loc);
+	    gimple_phi_set_result (new_phi, new_vop);
+	    FOR_EACH_IMM_USE_STMT (stmt, imm_iter, vop)
+	      if (stmt != new_phi && gimple_bb (stmt) != loop->header)
+		FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
+		  SET_USE (use_p, new_vop);
+	  }
+	break;
+      }
 
   /* 1. Generate a copy of LOOP and put it on E (E is the entry/exit of LOOP).
         Resulting CFG would be:
--- gcc/testsuite/gcc.c-torture/compile/pr52255.c.jj	2012-02-15 20:16:23.060799290 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr52255.c	2012-02-15 20:16:05.000000000 +0100
@@ -0,0 +1,12 @@
+/* PR tree-optimization/52255 */
+
+int a, b, c[10], d[10] = { 0, 0 };
+
+void
+foo (void)
+{
+  for (a = 1; a <= 4; a += 1)
+    d[a] = d[1];
+  for (; b; ++b)
+    c[0] |= 1;
+}

	Jakub