[PATCH] Fix PR59993

[Richard Biener]

This fixes an oversight with the (p + o1) + o2 association with
respect to abnormal-used SSA names.  I've also added a single-use
test so we don't add extra computations.

Bootstrap and regtest running on x86_64-unknown-linux-gnu.

Richard.

2014-01-30  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/59993
        * tree-ssa-forwprop.c (associate_pointerplus): Check we
        can propagate form the earlier stmt and avoid the transform
        when the intermediate result is needed.

        * gcc.dg/torture/pr59993.c: New testcase.

Index: gcc/tree-ssa-forwprop.c
===================================================================
*** gcc/tree-ssa-forwprop.c     (revision 207299)
--- gcc/tree-ssa-forwprop.c     (working copy)
*************** associate_pointerplus (gimple_stmt_itera
*** 2926,2936 ****
    /* Associate (p +p off1) +p off2 as (p +p (off1 + off2)).  */
    ptr = gimple_assign_rhs1 (stmt);
    off1 = gimple_assign_rhs2 (stmt);
!   if (TREE_CODE (ptr) != SSA_NAME)
      return false;
    def_stmt = SSA_NAME_DEF_STMT (ptr);
    if (!is_gimple_assign (def_stmt)
!       || gimple_assign_rhs_code (def_stmt) != POINTER_PLUS_EXPR)
      return false;
    ptr = gimple_assign_rhs1 (def_stmt);
    off2 = gimple_assign_rhs2 (def_stmt);
--- 2926,2938 ----
    /* Associate (p +p off1) +p off2 as (p +p (off1 + off2)).  */
    ptr = gimple_assign_rhs1 (stmt);
    off1 = gimple_assign_rhs2 (stmt);
!   if (TREE_CODE (ptr) != SSA_NAME
!       || !has_single_use (ptr))
      return false;
    def_stmt = SSA_NAME_DEF_STMT (ptr);
    if (!is_gimple_assign (def_stmt)
!       || gimple_assign_rhs_code (def_stmt) != POINTER_PLUS_EXPR
!       || !can_propagate_from (def_stmt))
      return false;
    ptr = gimple_assign_rhs1 (def_stmt);
    off2 = gimple_assign_rhs2 (def_stmt);
Index: gcc/testsuite/gcc.dg/torture/pr59993.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr59993.c      (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr59993.c      (working copy)
***************
*** 0 ****
--- 1,13 ----
+ /* { dg-do compile } */
+ 
+ #include <setjmp.h>
+ 
+ extern int optind;
+ jmp_buf jump_buf;
+ int
+ main (int argc, char **argv)
+ {
+   foo (jump_buf, setjmp(jump_buf));
+   argv += optind;
+   bar(argv[1]);
+ }