[PATCH] Fix PR71866

[PATCH] Fix PR71866

[Richard Biener]

The following fixes PR71866 and also includes some cleanup starting to
address the issue at a different level (we want to insert a & -1
as we didn't manage to simplify that during phi-translation - but
during insertion we _do_ simplify it and end up inserting nothing
but still report "progress", so we repeat that again and again).

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

2016-07-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/71866
	* tree-ssa-pre.c (get_constant_for_value_id): Remove.
	(do_hoist_insertion): Avoid endless recursion when we
	didn't insert anything because we managed to simplify
	things down to a constant or SSA name.
	(fully_constant_expression): Re-write in terms of ...
	* tree-ssa-sccvn.h (vn_nary_simplify): ... this.  Declare.
	* tree-ssa-sccvn.c (vn_nary_simplify): New wrapper around
	vn_nary_build_or_lookup_1.
	(vn_nary_build_or_lookup_1): Added flag and renamed from ...
	(vn_nary_build_or_lookup): ... this which now wraps it.

	* gcc.dg/torture/pr71866.c: New testcase.

Index: gcc/tree-ssa-pre.c
===================================================================
--- gcc/tree-ssa-pre.c	(revision 238287)
+++ gcc/tree-ssa-pre.c	(working copy)
@@ -1164,29 +1164,6 @@ get_or_alloc_expr_for_constant (tree con
   return newexpr;
 }
 
-/* Given a value id V, find the actual tree representing the constant
-   value if there is one, and return it. Return NULL if we can't find
-   a constant.  */
-
-static tree
-get_constant_for_value_id (unsigned int v)
-{
-  if (value_id_constant_p (v))
-    {
-      unsigned int i;
-      bitmap_iterator bi;
-      bitmap exprset = value_expressions[v];
-
-      EXECUTE_IF_SET_IN_BITMAP (exprset, 0, i, bi)
-	{
-	  pre_expr expr = expression_for_id (i);
-	  if (expr->kind == CONSTANT)
-	    return PRE_EXPR_CONSTANT (expr);
-	}
-    }
-  return NULL;
-}
-
 /* Get or allocate a pre_expr for a piece of GIMPLE, and return it.
    Currently only supports constants and SSA_NAMES.  */
 static pre_expr
@@ -1236,76 +1213,16 @@ fully_constant_expression (pre_expr e)
     case NARY:
       {
 	vn_nary_op_t nary = PRE_EXPR_NARY (e);
-	switch (TREE_CODE_CLASS (nary->opcode))
-	  {
-	  case tcc_binary:
-	  case tcc_comparison:
-	    {
-	      /* We have to go from trees to pre exprs to value ids to
-		 constants.  */
-	      tree naryop0 = nary->op[0];
-	      tree naryop1 = nary->op[1];
-	      tree result;
-	      if (!is_gimple_min_invariant (naryop0))
-		{
-		  pre_expr rep0 = get_or_alloc_expr_for (naryop0);
-		  unsigned int vrep0 = get_expr_value_id (rep0);
-		  tree const0 = get_constant_for_value_id (vrep0);
-		  if (const0)
-		    naryop0 = fold_convert (TREE_TYPE (naryop0), const0);
-		}
-	      if (!is_gimple_min_invariant (naryop1))
-		{
-		  pre_expr rep1 = get_or_alloc_expr_for (naryop1);
-		  unsigned int vrep1 = get_expr_value_id (rep1);
-		  tree const1 = get_constant_for_value_id (vrep1);
-		  if (const1)
-		    naryop1 = fold_convert (TREE_TYPE (naryop1), const1);
-		}
-	      result = fold_binary (nary->opcode, nary->type,
-				    naryop0, naryop1);
-	      if (result && is_gimple_min_invariant (result))
-		return get_or_alloc_expr_for_constant (result);
-	      /* We might have simplified the expression to a
-		 SSA_NAME for example from x_1 * 1.  But we cannot
-		 insert a PHI for x_1 unconditionally as x_1 might
-		 not be available readily.  */
-	      return e;
-	    }
-	  case tcc_reference:
-	    if (nary->opcode != REALPART_EXPR
-		&& nary->opcode != IMAGPART_EXPR
-		&& nary->opcode != VIEW_CONVERT_EXPR)
-	      return e;
-	    /* Fallthrough.  */
-	  case tcc_unary:
-	    {
-	      /* We have to go from trees to pre exprs to value ids to
-		 constants.  */
-	      tree naryop0 = nary->op[0];
-	      tree const0, result;
-	      if (is_gimple_min_invariant (naryop0))
-		const0 = naryop0;
-	      else
-		{
-		  pre_expr rep0 = get_or_alloc_expr_for (naryop0);
-		  unsigned int vrep0 = get_expr_value_id (rep0);
-		  const0 = get_constant_for_value_id (vrep0);
-		}
-	      result = NULL;
-	      if (const0)
-		{
-		  tree type1 = TREE_TYPE (nary->op[0]);
-		  const0 = fold_convert (type1, const0);
-		  result = fold_unary (nary->opcode, nary->type, const0);
-		}
-	      if (result && is_gimple_min_invariant (result))
-		return get_or_alloc_expr_for_constant (result);
-	      return e;
-	    }
-	  default:
-	    return e;
-	  }
+	tree res = vn_nary_simplify (nary);
+	if (!res)
+	  return e;
+	if (is_gimple_min_invariant (res))
+	  return get_or_alloc_expr_for_constant (res);
+	/* We might have simplified the expression to a
+	   SSA_NAME for example from x_1 * 1.  But we cannot
+	   insert a PHI for x_1 unconditionally as x_1 might
+	   not be available readily.  */
+	return e;
       }
     case REFERENCE:
       {
@@ -3618,10 +3552,18 @@ do_hoist_insertion (basic_block block)
       gimple_seq stmts = NULL;
       tree res = create_expression_by_pieces (block, expr, &stmts,
 					      get_expr_type (expr));
-      if (gsi_end_p (last) || is_ctrl_stmt (gsi_stmt (last)))
-	gsi_insert_seq_before (&last, stmts, GSI_SAME_STMT);
+
+      /* Do not return true if expression creation ultimately
+         did not insert any statements.  */
+      if (gimple_seq_empty_p (stmts))
+	res = NULL_TREE;
       else
-	gsi_insert_seq_after (&last, stmts, GSI_NEW_STMT);
+	{
+	  if (gsi_end_p (last) || is_ctrl_stmt (gsi_stmt (last)))
+	    gsi_insert_seq_before (&last, stmts, GSI_SAME_STMT);
+	  else
+	    gsi_insert_seq_after (&last, stmts, GSI_NEW_STMT);
+	}
 
       /* Make sure to not return true if expression creation ultimately
          failed but also make sure to insert any stmts produced as they

Index: gcc/tree-ssa-sccvn.c
===================================================================
*** gcc/tree-ssa-sccvn.c	(revision 238287)
--- gcc/tree-ssa-sccvn.c	(working copy)
*************** vn_lookup_simplify_result (code_helper r
*** 1625,1634 ****
  }
  
  /* Return a value-number for RCODE OPS... either by looking up an existing
!    value-number for the simplified result or by inserting the operation.  */
  
  static tree
! vn_nary_build_or_lookup (code_helper rcode, tree type, tree *ops)
  {
    tree result = NULL_TREE;
    /* We will be creating a value number for
--- 1625,1636 ----
  }
  
  /* Return a value-number for RCODE OPS... either by looking up an existing
!    value-number for the simplified result or by inserting the operation if
!    INSERT is true.  */
  
  static tree
! vn_nary_build_or_lookup_1 (code_helper rcode, tree type, tree *ops,
! 			   bool insert)
  {
    tree result = NULL_TREE;
    /* We will be creating a value number for
*************** vn_nary_build_or_lookup (code_helper rco
*** 1658,1664 ****
    else
      {
        tree val = vn_lookup_simplify_result (rcode, type, ops);
!       if (!val)
  	{
  	  gimple_seq stmts = NULL;
  	  result = maybe_push_res_to_seq (rcode, type, ops, &stmts);
--- 1660,1666 ----
    else
      {
        tree val = vn_lookup_simplify_result (rcode, type, ops);
!       if (!val && insert)
  	{
  	  gimple_seq stmts = NULL;
  	  result = maybe_push_res_to_seq (rcode, type, ops, &stmts);
*************** vn_nary_build_or_lookup (code_helper rco
*** 1719,1724 ****
--- 1721,1749 ----
    return result;
  }
  
+ /* Return a value-number for RCODE OPS... either by looking up an existing
+    value-number for the simplified result or by inserting the operation.  */
+ 
+ static tree
+ vn_nary_build_or_lookup (code_helper rcode, tree type, tree *ops)
+ {
+   return vn_nary_build_or_lookup_1 (rcode, type, ops, true);
+ }
+ 
+ /* Try to simplify the expression RCODE OPS... of type TYPE and return
+    its value if present.  */
+ 
+ tree
+ vn_nary_simplify (vn_nary_op_t nary)
+ {
+   if (nary->length > 3)
+     return NULL_TREE;
+   tree ops[3];
+   memcpy (ops, nary->op, sizeof (tree) * nary->length);
+   return vn_nary_build_or_lookup_1 (nary->opcode, nary->type, ops, false);
+ }
+ 
+ 
  /* Callback for walk_non_aliased_vuses.  Tries to perform a lookup
     from the statement defining VUSE and if not successful tries to
     translate *REFP and VR_ through an aggregate copy at the definition
Index: gcc/tree-ssa-sccvn.h
===================================================================
*** gcc/tree-ssa-sccvn.h	(revision 238287)
--- gcc/tree-ssa-sccvn.h	(working copy)
*************** unsigned int get_constant_value_id (tree
*** 234,239 ****
--- 234,240 ----
  unsigned int get_or_alloc_constant_value_id (tree);
  bool value_id_constant_p (unsigned int);
  tree fully_constant_vn_reference_p (vn_reference_t);
+ tree vn_nary_simplify (vn_nary_op_t);
  
  /* Valueize NAME if it is an SSA name, otherwise just return it.  */
  
Index: gcc/testsuite/gcc.dg/torture/pr71866.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr71866.c	(revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr71866.c	(working copy)
@@ -0,0 +1,40 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-ftree-pre -fcode-hoisting" } */
+
+typedef unsigned char u8;
+extern unsigned long pci_io_base;
+u8 in_8 (const volatile void *);
+int eeh_enabled ();
+void eeh_check_failure ();
+static inline 
+u8 eeh_readb(const volatile void *addr)
+{
+  u8 val = in_8(addr);
+  if (((val) == (u8)~0 && eeh_enabled()))   eeh_check_failure();
+  return val;
+}
+extern struct ppc_pci_io {
+    void (*outb) (u8 val, unsigned long port);
+}
+ppc_pci_io;
+static inline
+u8 readb (const volatile void * addr)
+{
+  return eeh_readb((addr));
+}
+static inline
+u8 inb (unsigned long port)
+{
+  return readb((volatile void *)pci_io_base + port);
+}
+static inline
+void outb (u8 val, unsigned long port)
+{
+  if (ppc_pci_io.outb != ((void *)0)) ppc_pci_io.outb (val, port);
+};
+void frob_econtrol(unsigned long base_hi, unsigned char m, unsigned char v)
+{
+  unsigned char ectr = 0;
+  if (m != 0xff)   ectr = inb((base_hi + 0x2));
+  outb((ectr & ~m) ^ v, (base_hi + 0x2));
+}