tree-optimization/93381 fix integer offsetting in points-to analysis

We were incorrectly assuming a merge operation is conservative enough
for not explicitely handled operations but we also need to consider
offsetting within fields when field-sensitive analysis applies.

2020-01-22  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/93381
	* tree-ssa-structalias.c (find_func_aliases): Assume offsetting
	throughout, handle all conversions the same.

	* gcc.dg/torture/pr93381.c: New testcase.

gcc/ChangeLog

+2020-01-22  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/93381
+	* tree-ssa-structalias.c (find_func_aliases): Assume offsetting
+	throughout, handle all conversions the same.
+
 2020-01-22  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/93335

gcc/testsuite/ChangeLog

+2020-01-22  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/93381
+	* gcc.dg/torture/pr93381.c: New testcase.
+
 2020-01-22  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/93335

gcc/testsuite/gcc.dg/torture/pr93381.c

+/* { dg-do run } */
+
+static struct S { int *p1; int *p2; } s;
+typedef __UINTPTR_TYPE__ uintptr_t;
+int foo()
+{
+  int i = 1, j = 2;
+  struct S s;
+  int **p;
+  s.p1 = &i;
+  s.p2 = &j;
+  p = &s.p1;
+  uintptr_t pi = (uintptr_t)p;
+  pi = pi + sizeof (int *);
+  p = (int **)pi;
+  **p = 3;
+  return j;
+}
+
+int main()
+{
+  if (foo () != 3)
+    __builtin_abort ();
+  return 0;
+}

gcc/tree-ssa-structalias.c

@@ -5008,11 +5008,12 @@ find_func_aliases (struct function *fn, gimple *origt)
 		   || code == FLOOR_MOD_EXPR
 		   || code == ROUND_MOD_EXPR)
 	    /* Division and modulo transfer the pointer from the LHS.  */
-	    get_constraint_for_rhs (gimple_assign_rhs1 (t), &rhsc);
-	  else if ((CONVERT_EXPR_CODE_P (code)
-		    && !(POINTER_TYPE_P (gimple_expr_type (t))
-			 && !POINTER_TYPE_P (TREE_TYPE (rhsop))))
+	    get_constraint_for_ptr_offset (gimple_assign_rhs1 (t),
+					   NULL_TREE, &rhsc);
+	  else if (CONVERT_EXPR_CODE_P (code)
 		   || gimple_assign_single_p (t))
+	    /* See through conversions, single RHS are handled by
+	       get_constraint_for_rhs.  */
 	    get_constraint_for_rhs (rhsop, &rhsc);
 	  else if (code == COND_EXPR)
 	    {
@@ -5031,14 +5032,16 @@ find_func_aliases (struct function *fn, gimple *origt)
 	    ;
 	  else
 	    {
-	      /* All other operations are merges.  */
+	      /* All other operations are possibly offsetting merges.  */
 	      auto_vec<ce_s, 4> tmp;
 	      struct constraint_expr *rhsp;
 	      unsigned i, j;
-	      get_constraint_for_rhs (gimple_assign_rhs1 (t), &rhsc);
+	      get_constraint_for_ptr_offset (gimple_assign_rhs1 (t),
+					     NULL_TREE, &rhsc);
 	      for (i = 2; i < gimple_num_ops (t); ++i)
 		{
-		  get_constraint_for_rhs (gimple_op (t, i), &tmp);
+		  get_constraint_for_ptr_offset (gimple_op (t, i),
+						 NULL_TREE, &tmp);
 		  FOR_EACH_VEC_ELT (tmp, j, rhsp)
 		    rhsc.safe_push (*rhsp);
 		  tmp.truncate (0);