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[PATCH] Fix PR28935, infinite loop folding due to fold_stmt deficiency


We end up calling fold on 0 != 0 ? 1 : 0 from VRP through the propagator 
engine.  fold_stmt fails to recursively fold 0 != 0, so the unfolded 
expression is passed to fold which is a bug as fold expects subexpressions
that are properly folded.

Fixed by teaching fold_stmt_r how to fold the condition of a COND_EXPR.

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

Ok for mainline?

Thanks,
Richard.

:ADDPATCH middle-end:

2006-09-02  Richard Guenther  <rguenther@suse.de>

	PR middle-end/28935
	* tree-ssa-ccp.c (fold_stmt_r): Make sure to fold the condition
	of a COND_EXPR.

	* gcc.dg/pr28935.c: New testcase.

Index: tree-ssa-ccp.c
===================================================================
*** tree-ssa-ccp.c	(revision 116660)
--- tree-ssa-ccp.c	(working copy)
*************** fold_stmt_r (tree *expr_p, int *walk_sub
*** 2043,2048 ****
--- 2043,2060 ----
        t = maybe_fold_tmr (expr);
        break;
  
+     case COND_EXPR:
+       if (COMPARISON_CLASS_P (TREE_OPERAND (expr, 0)))
+         {
+ 	  tree op0 = TREE_OPERAND (expr, 0);
+           tree tem = fold_binary (TREE_CODE (op0), TREE_TYPE (op0),
+ 				  TREE_OPERAND (op0, 0), TREE_OPERAND (op0, 1));
+ 	  if (tem && is_gimple_condexpr (tem))
+ 	    TREE_OPERAND (expr, 0) = tem;
+ 	  t = expr;
+           break;
+         }
+ 
      default:
        return NULL_TREE;
      }
Index: testsuite/gcc.dg/pr28935.c
===================================================================
*** testsuite/gcc.dg/pr28935.c	(revision 0)
--- testsuite/gcc.dg/pr28935.c	(revision 0)
***************
*** 0 ****
--- 1,15 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O3 -ftree-vectorize" } */
+ 
+ int col[8];
+ int extend_options(int w, int h, int *map, int x, int y, int index)
+ {
+   int dx, dy;
+   for (dx = -1; dx <= +1; dx++)
+     {
+       int index = (dy < 0 ? 6-dx : dy > 0 ? 2+dx : 2*(1+dx));
+       if (x+dx >= 0 && x+dx < w && y+dy >= 0 && y+dy < h)
+         col[index] = map[(y+dy)*w+(x+dx)];
+       col[index] = -1;
+     }
+ }


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