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Re: [PATCH][4.3][RFT] Fix PR37868, backport some PTA fixes


On Mon, 3 Nov 2008, Richard Guenther wrote:

> On Sat, 25 Oct 2008, Eric Botcazou wrote:
> 
> > > Still this is a quite big patch - so I appreciate testing and won't
> > > install this at the moment.
> > 
> > Tested locally (C/C++/Ada) on i586-suse-linux and run through AdaCore's 
> > internal testsuite on x86 and x86-64.  No problems detected.
> 
> Thanks for testing.  I'll throw it on openSUSE and likely will apply it
> if there are no problems detected.  Other opinions welcome of course.

Successfully tested on our other architectures and with a re-build of
openSUSE packages.  Applied to the branch.

Patch appended for reference.  I'll apply the new testcases to the
trunk as well.

Richard.

2008-11-20  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/37868
	* tree-ssa-structalias.c (set_uids_in_ptset): Add SFTs based on
	pointed to variable and access size.

	* gcc.dg/torture/pr37868.c: New testcase.
	* gcc.c-torture/execute/pr38048-1.c: Likewise.
	* gcc.c-torture/execute/pr38048-2.c: Likewise.

	Backport from mainline:
	2008-07-07  Richard Guenther  <rguenther@suse.de>

        * tree-ssa-structalias.c (struct variable_info): Add is_full_var flag.
        (new_var_info): Set it to false.
        (solution_set_add): Correctly handle pointers outside a var and
        inside a field.
        (type_safe): Treat variables with is_full_var properly.
        (do_sd_constraint): Likewise.
        (do_ds_constraint): Likewise.
        (process_constraint): Remove zeroing offset for !use_field_sensitive.
        (get_constraint_for_ptr_offset): New function.
        (get_constraint_for_component_ref): Handle is_full_vars properly.
        (get_constraint_for): Handle POINTER_PLUS_EXPR.
        (handle_ptr_arith): Remove.
        (find_func_aliases): Handle POINTER_PLUS_EXPR through generic
	get_constraint_for code.
        (create_function_info_for): For parameter and result varinfos set
        is_full_var flag.
        (create_variable_info_for): Set is_full_var flag whenever we
        just created a single varinfo for a decl.
        (init_alias_vars): Initialize use_field_sensitive from
        max-fields-for-field-sensitive parameter.

	* gcc.dg/torture/pta-ptrarith-1.c: New testcase.
	* gcc.dg/torture/pta-ptrarith-2.c: Likewise.

Index: gcc-4_3-branch/gcc/testsuite/gcc.dg/torture/pta-ptrarith-1.c
===================================================================
*** /dev/null	1970-01-01 00:00:00.000000000 +0000
--- gcc-4_3-branch/gcc/testsuite/gcc.dg/torture/pta-ptrarith-1.c	2008-10-22 15:28:30.000000000 +0200
***************
*** 0 ****
--- 1,29 ----
+ /* { dg-do run } */
+ 
+ struct Foo {
+   int *p;
+ };
+ 
+ void __attribute__((noinline))
+ foo (void *p)
+ {
+   struct Foo *f = (struct Foo *)p - 1;
+   *f->p = 0;
+ }
+ 
+ int bar (void)
+ {
+   struct Foo f;
+   int i = 1;
+   f.p = &i;
+   foo (&f + 1);
+   return i;
+ }
+ extern void abort (void);
+ int main()
+ {
+   if (bar () != 0)
+     abort ();
+   return 0;
+ }
+ 
Index: gcc-4_3-branch/gcc/testsuite/gcc.dg/torture/pta-ptrarith-2.c
===================================================================
*** /dev/null	1970-01-01 00:00:00.000000000 +0000
--- gcc-4_3-branch/gcc/testsuite/gcc.dg/torture/pta-ptrarith-2.c	2008-10-22 15:28:30.000000000 +0200
***************
*** 0 ****
--- 1,36 ----
+ /* { dg-do run } */
+ /* { dg-options "-fdump-tree-salias" } */
+ /* { dg-skip-if "" { *-*-* } { "-O0" } { "" } } */
+ 
+ struct Foo {
+   int **p;
+   int **q;
+ };
+ 
+ int __attribute__((noinline))
+ bar (void)
+ {
+   struct Foo f;
+   int j, i = 1;
+   char *p;
+   int *x = &i;
+   int *y = &j;
+   f.p = &y;
+   f.q = &x;
+   p = (char *)&f;
+   for (j = 0; j < sizeof (int *); ++j)
+     p++;
+   return ***(int ***)p;
+ }
+ extern void abort (void);
+ int main()
+ {
+   if (bar () != 1)
+     abort ();
+   return 0;
+ }
+ 
+ /* In theory = { i } is the correct solution.  But it's not easy to scan
+    for that reliably, so just use what we create now.  */
+ /* { dg-final { scan-tree-dump "= { i j }" "salias" } } */
+ /* { dg-final { cleanup-tree-dump "salias" } } */
Index: gcc-4_3-branch/gcc/tree-ssa-structalias.c
===================================================================
*** gcc-4_3-branch.orig/gcc/tree-ssa-structalias.c	2008-10-22 15:28:17.000000000 +0200
--- gcc-4_3-branch/gcc/tree-ssa-structalias.c	2008-10-22 18:12:58.000000000 +0200
***************
*** 241,246 ****
--- 241,249 ----
    /* True for variables that have unions somewhere in them.  */
    unsigned int has_union:1;
  
+   /* True for (sub-)fields that represent a whole variable.  */
+   unsigned int is_full_var : 1;
+ 
    /* True if this is a heap variable.  */
    unsigned int is_heap_var:1;
  
***************
*** 363,368 ****
--- 366,372 ----
    ret->is_heap_var = false;
    ret->is_special_var = false;
    ret->is_unknown_size_var = false;
+   ret->is_full_var = false;
    ret->has_union = false;
    var = t;
    if (TREE_CODE (var) == SSA_NAME)
***************
*** 742,764 ****
  
    EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
      {
!       /* If this is a properly sized variable, only add offset if it's
! 	 less than end.  Otherwise, it is globbed to a single
! 	 variable.  */
  
!       if ((get_varinfo (i)->offset + offset) < get_varinfo (i)->fullsize)
  	{
! 	  unsigned HOST_WIDE_INT fieldoffset = get_varinfo (i)->offset + offset;
! 	  varinfo_t v = first_vi_for_offset (get_varinfo (i), fieldoffset);
  	  if (!v)
! 	    continue;
  	  bitmap_set_bit (result, v->id);
! 	}
!       else if (get_varinfo (i)->is_artificial_var
! 	       || get_varinfo (i)->has_union
! 	       || get_varinfo (i)->is_unknown_size_var)
! 	{
! 	  bitmap_set_bit (result, i);
  	}
      }
  
--- 746,778 ----
  
    EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
      {
!       varinfo_t vi = get_varinfo (i);
  
!       /* If this is a variable with just one field just set its bit
! 	 in the result.  */
!       if (vi->is_artificial_var
! 	  || vi->is_unknown_size_var
! 	  || vi->has_union
! 	  || vi->is_full_var)
! 	bitmap_set_bit (result, i);
!       else
  	{
! 	  unsigned HOST_WIDE_INT fieldoffset = vi->offset + offset;
! 	  varinfo_t v = first_vi_for_offset (vi, fieldoffset);
! 	  /* If the result is outside of the variable use the last field.  */
  	  if (!v)
! 	    {
! 	      v = vi;
! 	      while (v->next != NULL)
! 		v = v->next;
! 	    }
  	  bitmap_set_bit (result, v->id);
! 	  /* If the result is not exactly at fieldoffset include the next
! 	     field as well.  See get_constraint_for_ptr_offset for more
! 	     rationale.  */
! 	  if (v->offset != fieldoffset
! 	      && v->next != NULL)
! 	    bitmap_set_bit (result, v->next->id);
  	}
      }
  
***************
*** 1371,1377 ****
       0.  */
    if (ninfo->is_special_var
        || ninfo->is_artificial_var
!       || ninfo->is_unknown_size_var)
      {
        *offset = 0;
        return true;
--- 1385,1392 ----
       0.  */
    if (ninfo->is_special_var
        || ninfo->is_artificial_var
!       || ninfo->is_unknown_size_var
!       || ninfo->is_full_var)
      {
        *offset = 0;
        return true;
***************
*** 1411,1416 ****
--- 1426,1432 ----
  	  unsigned int t;
  
  	  v = first_vi_for_offset (get_varinfo (j), fieldoffset);
+ 	  /* If the access is outside of the variable we can ignore it.  */
  	  if (!v)
  	    continue;
  	  t = find (v->id);
***************
*** 1460,1468 ****
  	 unsigned HOST_WIDE_INT fieldoffset = jvi->offset + loff;
  	 varinfo_t v;
  
! 	 v = first_vi_for_offset (get_varinfo (j), fieldoffset);
! 	 if (!v)
! 	   continue;
  	 t = find (v->id);
  
  	 if (!bitmap_bit_p (get_varinfo (t)->solution, anything_id))
--- 1476,1489 ----
  	 unsigned HOST_WIDE_INT fieldoffset = jvi->offset + loff;
  	 varinfo_t v;
  
! 	 v = get_varinfo (j);
! 	 if (!v->is_full_var)
! 	   {
! 	     v = first_vi_for_offset (v, fieldoffset);
! 	     /* If the access is outside of the variable we can ignore it.  */
! 	     if (!v)
! 	       continue;
! 	   }
  	 t = find (v->id);
  
  	 if (!bitmap_bit_p (get_varinfo (t)->solution, anything_id))
***************
*** 1491,1496 ****
--- 1512,1518 ----
  	  bitmap tmp;
  
  	  v = first_vi_for_offset (get_varinfo (j), fieldoffset);
+ 	  /* If the access is outside of the variable we can ignore it.  */
  	  if (!v)
  	    continue;
  	  t = find (v->id);
***************
*** 2519,2530 ****
    gcc_assert (rhs.var < VEC_length (varinfo_t, varmap));
    gcc_assert (lhs.var < VEC_length (varinfo_t, varmap));
  
-   if (!use_field_sensitive)
-     {
-       t->rhs.offset = 0;
-       t->lhs.offset = 0;
-     }
- 
    /* ANYTHING == ANYTHING is pointless.  */
    if (lhs.var == anything_id && rhs.var == anything_id)
      return;
--- 2541,2546 ----
***************
*** 2593,2600 ****
    tree type = TREE_TYPE (t);
  
    if (POINTER_TYPE_P (type)
!       || AGGREGATE_TYPE_P (type)
!       || TREE_CODE (type) == COMPLEX_TYPE)
      return true;
  
    return false;
--- 2609,2615 ----
    tree type = TREE_TYPE (t);
  
    if (POINTER_TYPE_P (type)
!       || AGGREGATE_TYPE_P (type))
      return true;
  
    return false;
***************
*** 2635,2640 ****
--- 2650,2769 ----
    return false;
  }
  
+ 
+ /* Get constraint expressions for offsetting PTR by OFFSET.  Stores the
+    resulting constraint expressions in *RESULTS.  */
+ 
+ static void
+ get_constraint_for_ptr_offset (tree ptr, tree offset,
+ 			       VEC (ce_s, heap) **results)
+ {
+   struct constraint_expr *c;
+   unsigned int j, n;
+   unsigned HOST_WIDE_INT rhsunitoffset, rhsoffset;
+ 
+   /* If we do not do field-sensitive PTA adding offsets to pointers
+      does not change the points-to solution.  */
+   if (!use_field_sensitive)
+     {
+       get_constraint_for (ptr, results);
+       return;
+     }
+ 
+   /* If the offset is not a non-negative integer constant that fits
+      in a HOST_WIDE_INT, we have to fall back to a conservative
+      solution which includes all sub-fields of all pointed-to
+      variables of ptr.
+      ???  As we do not have the ability to express this, fall back
+      to anything.  */
+   if (!host_integerp (offset, 1))
+     {
+       struct constraint_expr temp;
+       temp.var = anything_id;
+       temp.type = SCALAR;
+       temp.offset = 0;
+       VEC_safe_push (ce_s, heap, *results, &temp);
+       return;
+     }
+ 
+   /* Make sure the bit-offset also fits.  */
+   rhsunitoffset = TREE_INT_CST_LOW (offset);
+   rhsoffset = rhsunitoffset * BITS_PER_UNIT;
+   if (rhsunitoffset != rhsoffset / BITS_PER_UNIT)
+     {
+       struct constraint_expr temp;
+       temp.var = anything_id;
+       temp.type = SCALAR;
+       temp.offset = 0;
+       VEC_safe_push (ce_s, heap, *results, &temp);
+       return;
+     }
+ 
+   get_constraint_for (ptr, results);
+   if (rhsoffset == 0)
+     return;
+ 
+   /* As we are eventually appending to the solution do not use
+      VEC_iterate here.  */
+   n = VEC_length (ce_s, *results);
+   for (j = 0; j < n; j++)
+     {
+       varinfo_t curr;
+       c = VEC_index (ce_s, *results, j);
+       curr = get_varinfo (c->var);
+ 
+       if (c->type == ADDRESSOF
+ 	  && !curr->is_full_var)
+ 	{
+ 	  varinfo_t temp, curr = get_varinfo (c->var);
+ 
+ 	  /* Search the sub-field which overlaps with the
+ 	     pointed-to offset.  As we deal with positive offsets
+ 	     only, we can start the search from the current variable.  */
+ 	  temp = first_vi_for_offset (curr, curr->offset + rhsoffset);
+ 
+ 	  /* If the result is outside of the variable we have to provide
+ 	     a conservative result, as the variable is still reachable
+ 	     from the resulting pointer (even though it technically
+ 	     cannot point to anything).  The last sub-field is such
+ 	     a conservative result.
+ 	     ???  If we always had a sub-field for &object + 1 then
+ 	     we could represent this in a more precise way.  */
+ 	  if (temp == NULL)
+ 	    {
+ 	      temp = curr;
+ 	      while (temp->next != NULL)
+ 		temp = temp->next;
+ 	      continue;
+ 	    }
+ 
+ 	  /* If the found variable is not exactly at the pointed to
+ 	     result, we have to include the next variable in the
+ 	     solution as well.  Otherwise two increments by offset / 2
+ 	     do not result in the same or a conservative superset
+ 	     solution.  */
+ 	  if (temp->offset != curr->offset + rhsoffset
+ 	      && temp->next != NULL)
+ 	    {
+ 	      struct constraint_expr c2;
+ 	      c2.var = temp->next->id;
+ 	      c2.type = ADDRESSOF;
+ 	      c2.offset = 0;
+ 	      VEC_safe_push (ce_s, heap, *results, &c2);
+ 	    }
+ 	  c->var = temp->id;
+ 	  c->offset = 0;
+ 	}
+       else if (c->type == ADDRESSOF
+ 	       /* If this varinfo represents a full variable just use it.  */
+ 	       && curr->is_full_var)
+ 	c->offset = 0;
+       else
+ 	c->offset = rhsoffset;
+     }
+ }
+ 
+ 
  /* Given a COMPONENT_REF T, return the constraint_expr for it.  */
  
  static void
***************
*** 2682,2688 ****
    if (TREE_CODE (t) != ADDR_EXPR && result->type == ADDRESSOF)
      result->type = SCALAR;
  
!   if (result->type == SCALAR)
      {
        /* In languages like C, you can access one past the end of an
  	 array.  You aren't allowed to dereference it, so we can
--- 2811,2821 ----
    if (TREE_CODE (t) != ADDR_EXPR && result->type == ADDRESSOF)
      result->type = SCALAR;
  
!   if (result->type == SCALAR
!       && get_varinfo (result->var)->is_full_var)
!     /* For single-field vars do not bother about the offset.  */
!     result->offset = 0;
!   else if (result->type == SCALAR)
      {
        /* In languages like C, you can access one past the end of an
  	 array.  You aren't allowed to dereference it, so we can
***************
*** 2801,2833 ****
  	      struct constraint_expr *c;
  	      unsigned int i;
  	      tree exp = TREE_OPERAND (t, 0);
- 	      tree pttype = TREE_TYPE (TREE_TYPE (t));
  
  	      get_constraint_for (exp, results);
  
- 
- 	      /* Complex types are special. Taking the address of one
- 		 allows you to access either part of it through that
- 		 pointer.  */
- 	      if (VEC_length (ce_s, *results) == 1 &&
- 		  TREE_CODE (pttype) == COMPLEX_TYPE)
- 		{
- 		  struct constraint_expr *origrhs;
- 		  varinfo_t origvar;
- 		  struct constraint_expr tmp;
- 
- 		  gcc_assert (VEC_length (ce_s, *results) == 1);
- 		  origrhs = VEC_last (ce_s, *results);
- 		  tmp = *origrhs;
- 		  VEC_pop (ce_s, *results);
- 		  origvar = get_varinfo (origrhs->var);
- 		  for (; origvar; origvar = origvar->next)
- 		    {
- 		      tmp.var = origvar->id;
- 		      VEC_safe_push (ce_s, heap, *results, &tmp);
- 		    }
- 		}
- 
  	      for (i = 0; VEC_iterate (ce_s, *results, i, c); i++)
  		{
  		  if (c->type == DEREF)
--- 2934,2942 ----
***************
*** 2943,2948 ****
--- 3052,3067 ----
  	    }
  	  }
        }
+     case tcc_binary:
+       {
+ 	if (TREE_CODE (t) == POINTER_PLUS_EXPR)
+ 	  {
+ 	    get_constraint_for_ptr_offset (TREE_OPERAND (t, 0),
+ 					   TREE_OPERAND (t, 1), results);
+ 	    return;
+ 	  }
+ 	break;
+       }
      case tcc_exceptional:
        {
  	switch (TREE_CODE (t))
***************
*** 3512,3590 ****
  }
  
  
- /* Handle pointer arithmetic EXPR when creating aliasing constraints.
-    Expressions of the type PTR + CST can be handled in two ways:
- 
-    1- If the constraint for PTR is ADDRESSOF for a non-structure
-       variable, then we can use it directly because adding or
-       subtracting a constant may not alter the original ADDRESSOF
-       constraint (i.e., pointer arithmetic may not legally go outside
-       an object's boundaries).
- 
-    2- If the constraint for PTR is ADDRESSOF for a structure variable,
-       then if CST is a compile-time constant that can be used as an
-       offset, we can determine which sub-variable will be pointed-to
-       by the expression.
- 
-    Return true if the expression is handled.  For any other kind of
-    expression, return false so that each operand can be added as a
-    separate constraint by the caller.  */
- 
- static bool
- handle_ptr_arith (VEC (ce_s, heap) *lhsc, tree expr)
- {
-   tree op0, op1;
-   struct constraint_expr *c, *c2;
-   unsigned int i = 0;
-   unsigned int j = 0;
-   VEC (ce_s, heap) *temp = NULL;
-   unsigned HOST_WIDE_INT rhsunitoffset, rhsoffset;
- 
-   if (TREE_CODE (expr) != POINTER_PLUS_EXPR)
-     return false;
- 
-   op0 = TREE_OPERAND (expr, 0);
-   op1 = TREE_OPERAND (expr, 1);
-   gcc_assert (POINTER_TYPE_P (TREE_TYPE (op0)));
- 
-   /* If the offset is not a non-negative integer constant that fits
-      in a HOST_WIDE_INT, we cannot handle it here.  */
-   if (!host_integerp (op1, 1))
-     return false;
- 
-   /* Make sure the bit-offset also fits.  */
-   rhsunitoffset = TREE_INT_CST_LOW (op1);
-   rhsoffset = rhsunitoffset * BITS_PER_UNIT;
-   if (rhsunitoffset != rhsoffset / BITS_PER_UNIT)
-     return false;
- 
-   get_constraint_for (op0, &temp);
- 
-   for (i = 0; VEC_iterate (ce_s, lhsc, i, c); i++)
-     for (j = 0; VEC_iterate (ce_s, temp, j, c2); j++)
-       {
- 	if (c2->type == ADDRESSOF && rhsoffset != 0)
- 	  {
- 	    varinfo_t temp = get_varinfo (c2->var);
- 
- 	    /* An access one after the end of an array is valid,
- 	       so simply punt on accesses we cannot resolve.  */
- 	    temp = first_vi_for_offset (temp, rhsoffset);
- 	    if (temp == NULL)
- 	      continue;
- 	    c2->var = temp->id;
- 	    c2->offset = 0;
- 	  }
- 	else
- 	  c2->offset = rhsoffset;
- 	process_constraint (new_constraint (*c, *c2));
-       }
- 
-   VEC_free (ce_s, heap, temp);
- 
-   return true;
- }
- 
  /* For non-IPA mode, generate constraints necessary for a call on the
     RHS.  */
  
--- 3631,3636 ----
***************
*** 3815,3824 ****
        tree rhsop = GIMPLE_STMT_OPERAND (t, 1);
        int i;
  
!       if ((AGGREGATE_TYPE_P (TREE_TYPE (lhsop))
! 	   || TREE_CODE (TREE_TYPE (lhsop)) == COMPLEX_TYPE)
! 	  && (AGGREGATE_TYPE_P (TREE_TYPE (rhsop))
! 	      || TREE_CODE (TREE_TYPE (lhsop)) == COMPLEX_TYPE))
  	{
  	  do_structure_copy (lhsop, rhsop);
  	}
--- 3861,3868 ----
        tree rhsop = GIMPLE_STMT_OPERAND (t, 1);
        int i;
  
!       if (AGGREGATE_TYPE_P (TREE_TYPE (lhsop))
! 	  && AGGREGATE_TYPE_P (TREE_TYPE (rhsop)))
  	{
  	  do_structure_copy (lhsop, rhsop);
  	}
***************
*** 3842,3847 ****
--- 3886,3892 ----
  		  case tcc_expression:
  		  case tcc_vl_exp:
  		  case tcc_unary:
+ 		  case tcc_binary:
  		      {
  			unsigned int j;
  
***************
*** 3854,3874 ****
  			    for (k = 0; VEC_iterate (ce_s, rhsc, k, c2); k++)
  			      process_constraint (new_constraint (*c, *c2));
  			  }
- 
  		      }
  		    break;
  
- 		  case tcc_binary:
- 		      {
- 			/* For pointer arithmetic of the form
- 			   PTR + CST, we can simply use PTR's
- 			   constraint because pointer arithmetic is
- 			   not allowed to go out of bounds.  */
- 			if (handle_ptr_arith (lhsc, rhsop))
- 			  break;
- 		      }
- 		    /* FALLTHRU  */
- 
  		  /* Otherwise, walk each operand.  Notice that we
  		     can't use the operand interface because we need
  		     to process expressions other than simple operands
--- 3899,3907 ----
***************
*** 4257,4264 ****
    stats.total_vars++;
  
    /* If it's varargs, we don't know how many arguments it has, so we
!      can't do much.
!   */
    if (is_varargs)
      {
        vi->fullsize = ~0;
--- 4290,4296 ----
    stats.total_vars++;
  
    /* If it's varargs, we don't know how many arguments it has, so we
!      can't do much.  */
    if (is_varargs)
      {
        vi->fullsize = ~0;
***************
*** 4292,4297 ****
--- 4324,4330 ----
        VEC_safe_push (varinfo_t, heap, varmap, argvi);
        argvi->offset = i;
        argvi->size = 1;
+       argvi->is_full_var = true;
        argvi->fullsize = vi->fullsize;
        argvi->has_union = false;
        insert_into_field_list_sorted (vi, argvi);
***************
*** 4329,4334 ****
--- 4362,4368 ----
        resultvi->offset = i;
        resultvi->size = 1;
        resultvi->fullsize = vi->fullsize;
+       resultvi->is_full_var = true;
        resultvi->has_union = false;
        insert_into_field_list_sorted (vi, resultvi);
        stats.total_vars ++;
***************
*** 4464,4469 ****
--- 4498,4504 ----
  	  vi->is_unknown_size_var = 1;
  	  vi->fullsize = ~0;
  	  vi->size = ~0;
+ 	  vi->is_full_var = true;
  	  VEC_free (fieldoff_s, heap, fieldstack);
  	  return index;
  	}
***************
*** 4502,4507 ****
--- 4537,4544 ----
  	  stats.total_vars++;
  	}
      }
+   else
+     vi->is_full_var = true;
  
    VEC_free (fieldoff_s, heap, fieldstack);
  
***************
*** 4749,4765 ****
  	      && (sv = get_subvars_for_var (vi->decl)))
  	    {
  	      /* If VI->DECL is an aggregate for which we created
! 		 SFTs, add the SFT corresponding to VI->OFFSET.
  		 If we didn't do field-sensitive PTA we need to to
  		 add all overlapping SFTs.  */
  	      unsigned int j;
! 	      tree sft = get_first_overlapping_subvar (sv, vi->offset,
! 						       vi->size, &j);
  	      gcc_assert (sft);
  	      for (; VEC_iterate (tree, sv, j, sft); ++j)
  		{
  		  if (SFT_OFFSET (sft) > vi->offset
! 		      && vi->size <= SFT_OFFSET (sft) - vi->offset)
  		    break;
  
  		  bitmap_set_bit (into, DECL_UID (sft));
--- 4786,4807 ----
  	      && (sv = get_subvars_for_var (vi->decl)))
  	    {
  	      /* If VI->DECL is an aggregate for which we created
! 		 SFTs, add the SFT corresponding to VI->OFFSET (the
! 		 pointed-to location) and the access size.
  		 If we didn't do field-sensitive PTA we need to to
  		 add all overlapping SFTs.  */
  	      unsigned int j;
! 	      unsigned HOST_WIDE_INT size = -1;
! 	      tree sft, tsize = TYPE_SIZE (TREE_TYPE (TREE_TYPE (ptr)));
! 	      if (tsize
! 		  && host_integerp (tsize, 1))
! 		size = TREE_INT_CST_LOW (tsize);
! 	      sft = get_first_overlapping_subvar (sv, vi->offset, size, &j);
  	      gcc_assert (sft);
  	      for (; VEC_iterate (tree, sv, j, sft); ++j)
  		{
  		  if (SFT_OFFSET (sft) > vi->offset
! 		      && size <= SFT_OFFSET (sft) - vi->offset)
  		    break;
  
  		  bitmap_set_bit (into, DECL_UID (sft));
***************
*** 5156,5161 ****
--- 5198,5205 ----
  static void
  init_alias_vars (void)
  {
+   use_field_sensitive = (MAX_FIELDS_FOR_FIELD_SENSITIVE > 1);
+ 
    bitmap_obstack_initialize (&pta_obstack);
    bitmap_obstack_initialize (&oldpta_obstack);
    bitmap_obstack_initialize (&predbitmap_obstack);
Index: gcc-4_3-branch/gcc/testsuite/gcc.dg/torture/pr37868.c
===================================================================
*** /dev/null	1970-01-01 00:00:00.000000000 +0000
--- gcc-4_3-branch/gcc/testsuite/gcc.dg/torture/pr37868.c	2008-10-22 15:28:30.000000000 +0200
***************
*** 0 ****
--- 1,28 ----
+ /* { dg-do run } */
+ /* { dg-options "-fno-strict-aliasing" } */
+ 
+ extern void abort (void);
+ 
+ struct X {
+   unsigned char pad : 4;
+   unsigned int a : 32;
+   unsigned int b : 24;
+   unsigned int c : 6;
+ } __attribute__((packed));
+ 
+ int main (void)
+ {
+   struct X x;
+   unsigned int bad_bits;
+ 
+   x.pad = -1;
+   x.a = -1;
+   x.b = -1;
+   x.c = -1;
+ 
+   bad_bits = ((unsigned int)-1) ^ *(1+(unsigned int *) &x);
+   if (bad_bits != 0)
+     abort ();
+   return 0;
+ }
+ 
Index: gcc-4_3-branch/gcc/testsuite/gcc.c-torture/execute/pr38048-1.c
===================================================================
*** gcc-4_3-branch/gcc/testsuite/gcc.c-torture/execute/pr38048-1.c	(revision 0)
--- gcc-4_3-branch/gcc/testsuite/gcc.c-torture/execute/pr38048-1.c	(revision 0)
***************
*** 0 ****
--- 1,22 ----
+ extern void abort(void);
+ 
+ int foo ()
+ {
+   int mat[2][1];
+   int (*a)[1] = mat;
+   int det = 0;
+   int i;
+   mat[0][0] = 1;
+   mat[1][0] = 2;
+   for (i = 0; i < 2; ++i)
+     det += a[i][0];
+   return det;
+ }
+ 
+ int main()
+ {
+   if (foo () != 3)
+     abort ();
+   return 0;
+ }
+ 
Index: gcc-4_3-branch/gcc/testsuite/gcc.c-torture/execute/pr38048-2.c
===================================================================
*** gcc-4_3-branch/gcc/testsuite/gcc.c-torture/execute/pr38048-2.c	(revision 0)
--- gcc-4_3-branch/gcc/testsuite/gcc.c-torture/execute/pr38048-2.c	(revision 0)
***************
*** 0 ****
--- 1,28 ----
+ extern void abort (void);
+ 
+ static int inv_J(int a[][2])
+ {
+   int i, j;
+   int det = 0.0;
+    for (j=0; j<2; ++j)
+      det += a[j][0] + a[j][1];
+   return det;
+ }
+ 
+ int foo()
+ {
+   int mat[2][2];
+   mat[0][0] = 1;
+   mat[0][1] = 2;
+   mat[1][0] = 4;
+   mat[1][1] = 8;
+   return inv_J(mat);
+ }
+ 
+ int main()
+ {
+   if (foo () != 15)
+     abort ();
+   return 0;
+ }
+ 


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