On December 19, 2017 6:23:55 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>As the testcase shows, we weren't handling the case where we have
>_34 = MEM_REF[&b, 4B];
>- we would (if it exists) find the string length for b.a, but not
>for the second field. Using get_addr_stridx handles that well.
>The reason to use get_stridx on the MEM_REF first operand is to handle
>the case when the MEM_REF is based on SSA_NAME, that is something
>get_addr_stridx doesn't handle.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
>2017-12-19 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/83444
> * tree-ssa-strlen.c (strlen_check_and_optimize_stmt): For the
> character load case, if get_stridx on MEM_REF's operand doesn't
> look usable, retry with get_addr_stridx.
>
> * gcc.dg/strlenopt-38.c: New test.
>
>--- gcc/tree-ssa-strlen.c.jj 2017-12-19 08:43:35.000000000 +0100
>+++ gcc/tree-ssa-strlen.c 2017-12-19 12:52:37.007267178 +0100
>@@ -3155,14 +3155,27 @@ strlen_check_and_optimize_stmt (gimple_s
> {
> tree off = integer_zero_node;
> unsigned HOST_WIDE_INT coff = 0;
>- int idx = -1;
>+ int idx = 0;
> tree rhs1 = gimple_assign_rhs1 (stmt);
> if (code == MEM_REF)
> {
> idx = get_stridx (TREE_OPERAND (rhs1, 0));
>- off = TREE_OPERAND (rhs1, 1);
>+ if (idx > 0)
>+ {
>+ strinfo *si = get_strinfo (idx);
>+ if (si
>+ && si->nonzero_chars
>+ && TREE_CODE (si->nonzero_chars) == INTEGER_CST
>+ && (wi::to_widest (si->nonzero_chars)
>+ >= wi::to_widest (off)))
>+ off = TREE_OPERAND (rhs1, 1);
>+ else
>+ /* This case is not useful. See if get_addr_stridx
>+ returns something usable. */
>+ idx = 0;
>+ }
> }
>- else
>+ if (idx <= 0)
> idx = get_addr_stridx (rhs1, NULL_TREE, &coff);
> if (idx > 0)
> {
>--- gcc/testsuite/gcc.dg/strlenopt-38.c.jj 2017-12-19
>08:43:35.000000000 +0100
>+++ gcc/testsuite/gcc.dg/strlenopt-38.c 2017-12-19 12:53:19.006730543
>+0100
>@@ -36,3 +36,14 @@ baz (void)
> if (s.b[0] != 0)
> abort ();
> }
>+
>+void
>+boo (void)
>+{
>+ struct S s;
>+ strcpy (s.b, "012");
>+ strcpy (s.c, "");
>+ strcpy (s.b, s.c);
>+ if (strlen (s.b) != 0)
>+ abort ();
>+}
>
> Jakub
