Re: [PATCH] Fix PR79740

[Richard Biener <rguenther at suse dot de>]

On Tue, 28 Feb 2017, Richard Biener wrote:

> 
> Bootstrap / regtest running on x86_64-unknown-linux-gnu.
> 
> Richard.

The following is what I committed.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

Richard.

2017-02-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/79740
	* tree-ssa-sccvn.c (vn_nary_op_insert_into): Allow redundant
	inserts.
	(visit_nary_op): Insert the nary into the hashtable if we
	pattern-matched sth.
	* tree-ssa-pre.c (eliminate_insert): Robustify.

	* gcc.dg/torture/pr79740.c: New testcase.

Index: gcc/tree-ssa-sccvn.c
===================================================================
*** gcc/tree-ssa-sccvn.c	(revision 245772)
--- gcc/tree-ssa-sccvn.c	(working copy)
*************** vn_nary_op_insert_into (vn_nary_op_t vno
*** 2820,2825 ****
--- 2820,2834 ----
      vno->hashcode = vn_nary_op_compute_hash (vno);
  
    slot = table->find_slot_with_hash (vno, vno->hashcode, INSERT);
+   /* While we do not want to insert things twice it's awkward to
+      avoid it in the case where visit_nary_op pattern-matches stuff
+      and ends up simplifying the replacement to itself.  We then
+      get two inserts, one from visit_nary_op and one from
+      vn_nary_build_or_lookup.
+      So allow inserts with the same value number.  */
+   if (*slot && (*slot)->result == vno->result)
+     return *slot;
+ 
    gcc_assert (!*slot);
  
    *slot = vno;
*************** visit_nary_op (tree lhs, gassign *stmt)
*** 3544,3550 ****
  			  result = vn_nary_build_or_lookup (NOP_EXPR,
  							    type, ops);
  			  if (result)
! 			    return set_ssa_val_to (lhs, result);
  			}
  		      else
  			{
--- 3553,3563 ----
  			  result = vn_nary_build_or_lookup (NOP_EXPR,
  							    type, ops);
  			  if (result)
! 			    {
! 			      bool changed = set_ssa_val_to (lhs, result);
! 			      vn_nary_op_insert_stmt (stmt, result);
! 			      return changed;
! 			    }
  			}
  		      else
  			{
*************** visit_nary_op (tree lhs, gassign *stmt)
*** 3555,3561 ****
  							    TREE_TYPE (lhs),
  							    ops);
  			  if (result)
! 			    return set_ssa_val_to (lhs, result);
  			}
  		    }
  		}
--- 3568,3578 ----
  							    TREE_TYPE (lhs),
  							    ops);
  			  if (result)
! 			    {
! 			      bool changed = set_ssa_val_to (lhs, result);
! 			      vn_nary_op_insert_stmt (stmt, result);
! 			      return changed;
! 			    }
  			}
  		    }
  		}
Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c	(revision 245772)
--- gcc/tree-ssa-pre.c	(working copy)
*************** eliminate_push_avail (tree op)
*** 4099,4106 ****
  static tree
  eliminate_insert (gimple_stmt_iterator *gsi, tree val)
  {
!   gimple *stmt = gimple_seq_first_stmt (VN_INFO (val)->expr);
!   if (!is_gimple_assign (stmt)
        || (!CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt))
  	  && gimple_assign_rhs_code (stmt) != VIEW_CONVERT_EXPR
  	  && gimple_assign_rhs_code (stmt) != BIT_FIELD_REF
--- 4099,4110 ----
  static tree
  eliminate_insert (gimple_stmt_iterator *gsi, tree val)
  {
!   /* We can insert a sequence with a single assignment only.  */
!   gimple_seq stmts = VN_INFO (val)->expr;
!   if (!gimple_seq_singleton_p (stmts))
!     return NULL_TREE;
!   gassign *stmt = dyn_cast <gassign *> (gimple_seq_first_stmt (stmts));
!   if (!stmt
        || (!CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt))
  	  && gimple_assign_rhs_code (stmt) != VIEW_CONVERT_EXPR
  	  && gimple_assign_rhs_code (stmt) != BIT_FIELD_REF
*************** eliminate_insert (gimple_stmt_iterator *
*** 4116,4123 ****
    if (!leader)
      return NULL_TREE;
  
-   gimple_seq stmts = NULL;
    tree res;
    if (gimple_assign_rhs_code (stmt) == BIT_FIELD_REF)
      res = gimple_build (&stmts, BIT_FIELD_REF,
  			TREE_TYPE (val), leader,
--- 4120,4127 ----
    if (!leader)
      return NULL_TREE;
  
    tree res;
+   stmts = NULL;
    if (gimple_assign_rhs_code (stmt) == BIT_FIELD_REF)
      res = gimple_build (&stmts, BIT_FIELD_REF,
  			TREE_TYPE (val), leader,
Index: gcc/testsuite/gcc.dg/torture/pr79740.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr79740.c	(nonexistent)
--- gcc/testsuite/gcc.dg/torture/pr79740.c	(working copy)
***************
*** 0 ****
--- 1,19 ----
+ /* { dg-do compile } */
+ 
+ int a;
+ short b;
+ short fn1(unsigned short p1) { return p1 << a; }
+ 
+ int main()
+ {
+   short c;
+   int d = 4;
+   for (; b;)
+     {
+       c = d + 1;
+       fn1(c);
+       d = 0;
+     }
+   d++;
+   return 0;
+ }